Cobalt-Mediated η5-Pentadienyl/Alkyne [5 + 2] Cycloaddition Reactions: Substitution Effects, Bicyclic Synthesis, and Photochemical η4-Cycloheptadiene Demetalation

Article abstract of DOI:10.1021/acs.organomet.5b00346

The preparation of seven-membered carbocycles via traditional organic synthesis is difficult, yet essential, due to the prevalence of these moieties in bioactive compounds. As we report, the Co-mediated pentadienyl/alkyne [5 + 2] cycloaddition reaction generates kinetically stable η²,η³-cycloheptadienyl complexes in high yield at room temperature, which isomerize to the thermodynamically preferred η⁵-cycloheptadienyl complexes upon heating at 60-70 °C. Here we describe an extended investigation of this reaction manifold, exploring substituent effects and extending the reaction to tandem cycloaddition/nucleophilic cyclizations, generating fused bicyclic compounds. We also describe a new high-yielding photolytic method for the decomplexation of organic cycloheptadienes from Co(I) complexes. Both C₅Me₅ (Cp?) and C₅H₅ (Cp) half-sandwich complexes are active in [5 + 2] cycloaddition with alkynes, with Cp? generally providing higher yields of cycloheptadienyl complexes. Cp cycloheptadienyl complexes, however, are resistant to thermal η²,η³ ' η⁵ isomerization. The reaction remains limited to open pentadienyl complexes incorporating substituents in the terminal (1 and 5) positions, except for the unsubstituted CpCo(η⁵-cycloheptadienyl)⁺ complex, which is modestly reactive. Incorporation of tethered latent nucleophiles allows cyclization onto the intermediate cycloheptadienyl cations, producing bicyclo[5.3.0]decadiene and bicyclo[5.4.0]undecadiene systems with complete diastereocontrol. A selection of intermediate complexes have been crystallographically characterized. Addition of tethered malonate nucleophiles occurs reversibly with equilibration to a thermodynamic elimination product, while enolate nucleophiles cyclize reliably under kinetic control. The resulting bicyclic products are decomplexed in high (>90%) yield by UV photolysis in the presence of allyl bromide to provide the organic bicyclic diene with complete retention of ring fusion geometry and without double-bond isomerization.

Full text of DOI:10.1021/acs.organomet.5b00346

Article
pubs.acs.org/Organometallics
Cobalt-Mediated η5‑Pentadienyl/Alkyne [5 + 2] Cycloaddition
Reactions: Substitution Effects, Bicyclic Synthesis, and
Photochemical η4‑Cycloheptadiene Demetalation
Kai E. O. Ylijoki,*,† Andrew D. Kirk,‡ Sebastian Bocklein,‡,§ Ross D. Witherell,‡ and Jeffrey M. Stryker*,‡
̈
†Department of Chemistry, Saint Mary’s University, Halifax, Nova Scotia, Canada B3H 3C3
‡Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada T6G 2G2
S
* Supporting Information
ABSTRACT: The preparation of seven-membered carbocycles via traditional organic synthesis is difficult, yet essential, due to
the prevalence of these moieties in bioactive compounds. As we report, the Co-mediated pentadienyl/alkyne [5 + 2] cyclo-
addition reaction generates kinetically stable η2,η3-cycloheptadienyl complexes in high yield at room temperature, which
isomerize to the thermodynamically preferred η5-cycloheptadienyl complexes upon heating at 60−70 °C. Here we describe an
extended investigation of this reaction manifold, exploring substituent effects and extending the reaction to tandem
cycloaddition/nucleophilic cyclizations, generating fused bicyclic compounds. We also describe a new high-yielding photolytic
method for the decomplexation of organic cycloheptadienes from Co(I) complexes. Both C5Me5 (Cp*) and C5H5 (Cp) half-
sandwich complexes are active in [5 + 2] cycloaddition with alkynes, with Cp* generally providing higher yields of cyclo-
heptadienyl complexes. Cp cycloheptadienyl complexes, however, are resistant to thermal η2,η3 → η5 isomerization. The reaction
remains limited to open pentadienyl complexes incorporating substituents in the terminal (1 and 5) positions, except for the
unsubstituted CpCo(η5-cycloheptadienyl)+ complex, which is modestly reactive. Incorporation of tethered latent nucleophiles
allows cyclization onto the intermediate cycloheptadienyl cations, producing bicyclo[5.3.0]decadiene and bicyclo[5.4.0]-
undecadiene systems with complete diastereocontrol. A selection of intermediate complexes have been crystallographically
characterized. Addition of tethered malonate nucleophiles occurs reversibly with equilibration to a thermodynamic elimination
product, while enolate nucleophiles cyclize reliably under kinetic control. The resulting bicyclic products are decomplexed in high
(>90%) yield by UV photolysis in the presence of allyl bromide to provide the organic bicyclic diene with complete retention of
ring fusion geometry and without double-bond isomerization.
pentadienyl fragment, a reaction that generally requires
mediation by a transition metal.4 The reaction has traditionally
been hampered by poor control over the stoichiometry of
alkyne incorporation, with most reactions leading to complex
multicyclic systems. We have addressed this difficulty in our
recent disclosure5 of the [5 + 2] cycloaddition reaction of
alkynes with Cp*Co(η5-pentadienyl)+ cations (Cp* = η5-C5Me5),6
which proceeds with complete control of alkyne stoichiometry
and ring size, yielding cycloheptadienyl complexes (Scheme 1).
Under kinetic control, thermally stable η2,η3-cycloheptadienyl
complexes 2 are obtained for some substitution patterns, a
previously unprecedented coordination mode for unbridged
cycloheptadienyl systems.7
INTRODUCTION
■
Since the first report of the Diels−Alder reaction, cycloaddition
methodology has become a key component of the synthetic
organic chemist’s toolbox. This utility is largely due to the
formation of multiple carbon−carbon bonds in a single step,
often with excellent control of regiochemistry and stereoselec-
tivity. Thermal, photochemical, and metal-mediated cyclo-
addition reactions for the synthesis of small- and medium-sized
carbocycles have been developed, with four-, five-, and six-
membered rings receiving most of the attention (i.e., [2 + 2],
[3 + 2], and [4 + 2] cycloaddition reactions). In contrast, the
preparation of seven-membered rings by cycloaddition remains
less developed,1 despite the almost continuous discovery of
bioactive natural products with seven-membered-ring structures
in the core.2 One important pathway to access the seven-
membered ring is the formal [5 + 2] cycloaddition reaction,
which has a rich and varied history.3 Among unsolved problems
in [5 + 2] cycloaddition is the cyclization of an alkyne with a
Our interest in the cycloaddition chemistry of η5-pentadienyl
cobalt complexes 1 was piqued by our observation of allyl/alkyne
Received: April 27, 2015
Published: June 25, 2015
© 2015 American Chemical Society
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Scheme 1. Pentadienyl/Alkyne [5 + 2] Cycloaddition
the anomalous [3 + 2 + 2] cycloaddition reaction prompted us
to investigate directly the reactivity of alkynes with acyclic
pentadienyl complexes of cobalt. While the [5 + 2] cyclo-
addition reactions indeed proceed,5 the isolation of kinetically
stable η2,η3-cycloheptadienyl complexes 2, not observed during
the anomalous [3 + 2 + 2] reaction, clearly demonstrates that
the [5 + 2] cycloaddition is a mechanistically independent reac-
tion manifold. Here we describe an extended investigation of
(i) the effects of pentadienyl substitution and variation of the
ancillary ligand on cycloaddition reactivity and product dis-
tribution and (ii) a proof-of-principle extension of the [5 + 2]
reaction manifold to the synthesis of conjugated and non-
conjugated bicyclo[5.3.0]- and bicyclo[5.4.0]-diene ring sys-
tems. We also report a novel photolytic method for the efficient
decomplexation of cobalt η4-cycloheptadiene complexes in high
yield, addressing a longstanding problem in organocobalt
chemistry.
[3 + 2 + 2] cycloaddition reactions (eq 1) and anomalous
[3 + 2 + 2] cyclo-rearrangements of Cp*Co(η3-allyl)X
complexes upon treatment with alkynes (eqs 2 and 3).8,9 The
[3 + 2 + 2] reaction proceeds via a coordinatively unsaturated
RESULTS AND DISCUSSION
■
Cp*Co(η5-pentadienyl)/alkyne [5 + 2] Cycloaddition.
We began our investigations by preparing a series of mono-, di-,
and trisubstituted pentadienyl complexes (Scheme 2).5,6 Simple
Scheme 2. Preparation of η5-Pentadienyl Complexes from
1,3- and 1,4-Pentadienols
η3-allylmetal intermediate, which incorporates 2 equiv of ter-
minal alkyne to produce cationic Cp*Co(η5-cycloheptadienyl)+
complexes in reasonable yield. Corresponding reactions of
internal alkynes, however, afforded anomalous cycloaddition
products, proceeding in a superficially similar fashion to the
standard [3 + 2 + 2] reaction but producing unexpected sub-
stituent patterns in both the cycloheptadienyl ring (eq 2) and,
oddly, the ancillary cyclopentadienyl ligand (eq 3). Isotopic
1,3- and 1,4-pentadienols add to Cp*Co(C2H4)2 in the pres-
ence of HBF4·OEt2 to yield Cp*Co(η5-pentadienyl) cations 1
in reasonable to good yields. The yield decreases with an
increasing number of pentadienyl substituents, presumably due
to competing off-metal reactions. The air-stable complexes are
readily isolated and purified by benchtop chromatography. In
some cases, the purity was improved by an aqueous exchange of
2
(13C, H) labeling and synthetic studies established that these
reactions proceed by a carbon−carbon bond activation of an
intermediate η3-cyclopentadienyl ring, an unexpected electro-
philic cleavage of an unstrained ring system (eq 4).10
−
−
the BF4 counterion for PF6 .
Despite being coordinatively saturated, η5-pentadienyl
complexes 1a,c−e react smoothly with excess ethyne at room
temperature, providing the coordinatively saturated η2,η3-
cycloheptadienyl complexes 2a,c−e with excellent selectivity
and complete diastereocontrol (Table 1, entries 1−4 and
7−11). The complexes 2a,c,d could be quantitatively
isomerized to more typical η5-cycloheptadienyl complexes
3a,f,i by heating to 70 °C in CH2Cl2 (entries 1, 6, and 9). It
could be debated whether the isomerization is a thermal
β-hydride elimination/reinsertion process or is mediated by an
external basic agent from the solvent or glass. However, η2,η3-
cycloheptadienyl complex 2e, bearing two methyl groups
proximal (syn) to the metal (entry 10), is completely inert at
elevated temperature (see Figure 1 for the solid-state structure
Two decades ago, Spencer et al., showed that upon
protonation with HBF4 Cp*Co(η4-cyclopentadiene) and
Cp*Co(η5-cyclooctadiene) complexes undergo a suspiciously
similar C−C bond cleavage reaction, yielding ring-opened
cationic η5-pentadienyl complexes (eq 5).11 The possibility that
such a bond activation could be embedded in the mechanism of
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a
Table 1. Cp*Co(cycloheptadienyl)+ Synthesis via [5 + 2] Cycloaddition
b
c
entry
substrate
1a (R1 = Me; R2 ,R3, R4, R5 = H)
alkyne
R, R′ = H
R, R′ = Me
2/yield (%)
2a/98
3/yield (%)
1
2
3
3a/99
3b/99
1a
1a
R = H, R′ = OEt
3c:3c′ (2:1)/82
3c: R = H, R′ = OEt
3c′: R = OEt, R′ = H
3d:3d′ (2:1)/91
n
4
1a
R = H, R′ = Pr
n
3d: R = H, R′ = Pr
n
3d′: R = Pr, R′ = H
d
5
1b (R1, R2 = Me; R3, R4, R5 = H)
1c (R1 = Ph; R2, R3, R4 ,R5 = H)
1c
R, R′ = H
R, R′ = H
R, R′ = Me
R = H, R′ = TMS
R, R′ = H
R, R′ = H
R, R′ = Me
R, R′ = H
R, R′ = H
R, R′ = H
R, R′ = H
R, R′ = H
R, R′ = H
2b:3e (3.8:1)/68
2c/89
6
3f/99
7
3g/96
e
8
1c
3h/26 R = H, R′ = TMS
3i/99
9
1d (R1 = Et; R2, R3, R4, R5 = H)
1e (R1, R5 = Me; R2, R3, R4 = H)
1e
2d/91
2e/94
2f/85
10
11
12
13
14
15
16
17
1f (R1, R2, R3, R4, R5 = H)
1g (R2 = Me; R1, R3, R4, R5 = H)
1h (R3 = Me; R1, R2, R4, R5 = H)
1i (R1, R3 = Me; R2, R4, R5 = H)
1j (R1, R4 = Me; R2, R3, R5 = H)
1k (R1, R2, R4 = Me; R3,R5 = H)
a
Detailed conditions are reported in the Supporting Information; yields of products after SiO2 chromatography (3−4% MeOH in CH2Cl2) are given.
b
c
Conditions: ethyne (saturated solution in CH2Cl2), room temperature, 12−72 h (10 equiv of 2-butyne, room temperature, 72 h for 2f). As above,
d
but 40−60 °C, 24−72 h (room temperature, 72 h for 3f). An additional minor byproduct, tentatively identified as a [3 + 2 + 2] cycloadduct, is
e
detected in the 1H NMR spectrum of this product. Yield determined by 1H NMR integration using 1,3,5-trimethoxybenzene as an internal standard.
Scheme 3. Mechanism of η2,η3 → η5 Isomerization
Figure 1. X-ray structure diagram for [Cp*Co(η2,η3-1,5-dimethylcy-
cloheptadienyl)]+BF4− (2e), with non-hydrogen atoms represented by
thermal ellipsoids at the 20% probability level. Final residuals: R1 =
0.0312, wR2 = 0.0781.13
2-Butyne is also an effective coupling partner; however,
the cycloaddition reaction is considerably slower. To achieve
of complex 2e). This result clearly demonstrates that a
unimolecular β-hydride elimination mechanism is most likely
at play during isomerization. This mechanistic proposal
is supported by density functional theory (DFT) calcu-
lations, where the lowest energy mechanism entails
reversible dissociation of the η2-alkene moiety with conc-
omitant formation of an agostic allyl hydride intermediate
(Scheme 3).12 This hydride undergoes β-hydride elimina-
tion and reinsertion to form a second agostic hydride,
with subsequent dissociation of the C−H bond and associa-
tion of the free olefin to form the final η5-cycloheptadienyl
complex.
reasonable reaction rates, the system is heated to 40 °C; under
these conditions, formation of the intermediate η2,η3-cyclo-
heptadienyl complex is not observed and the reaction proceeds
directly to the η5-dimethylcycloheptadienyl complexes 3. The
lower barrier to isomerization is attributed to weaker
Co−alkene bonding arising from steric repulsion between the
alkene methyl groups and the Cp* ancillary ligand, leading to
facile alkene dissociation (2 → 5 in Scheme 3).12 Only
cycloadduct 2e, obtained from 1,5-dimethylpentadienyl com-
plex 1e (Table 1, entry 11), is kinetically stable under the reac-
tion conditionsthe η2,η3 → η5 isomerization is again blocked
by the syn-methyl substituents. The η2,η3-cycloheptadienyl
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complex 2e decomposes without isomerization at elevated
temperature, and the complex slowly decomposes in solution
at room temperature. Interestingly, the cycloadditions of
pentadienyl complexes 1c,e with 2-butyne proceed at room
temperature to yield the η5-cycloheptadienyl complexes 3g
(entry 7), characterized by X-ray diffraction (Figure 2), and
single isolable product, η5-cycloheptadienyl complex 3h, but in
poor yield (entry 8). While the product appears to be that
arising from a sterically controlled regioselective insertion of
the alkyne unit, the low yield suggests that the reaction is not
truly regioselective. For the alternate regioisomer to form, a
C−C bond must be formed between two secondary positions:
steric effects between the TMS and Me substituents are
expected to raise the TS energy for this process significantly,
allowing unproductive (and thus far uncharacterized) side
processes to become kinetically competitive. Trials with
phenylacetylene led to similarly complex crude product
mixtures and were not further investigated.
To our considerable consternation, pentadienyl complexes
lacking 1-substituents or bearing additional internal methyl
groups (i.e., 2- or 3-substituents) display considerably
attenuated reactivity. This trend is most clearly illustrated by
the reactions of ethyne with methylpentadienyl complexes
1a,g,h and the unsubstituted complex 1f (Table 1, entries 1,
12−14). Only the terminally substituted complex 1a is reactive;
neither unsubstituted complex 1f nor the 2- or 3-substituted
complexes 1h,g show any conversion to tractable products.
This trend immediately suggests that a 1-substituent is critical
for dissociative reactivity. Necessary, but not sufficient,
however: no reaction with ethyne is observed for the 1,3- or
1,4-dimethylated complexes 1i,j (entries 15 and 16) or for the
1,2,4-trisubstituted complex 1k (entry 17). Only the 1,2-
disubstituted pentadienyl complex 1b displays productive
reactivity and gives a reasonable yield (entry 5).
Figure 2. X-ray structure diagram for [Cp*Co(η5-cycloheptadienyl)]+BF4−
(3g), with non-hydrogen atoms represented by thermal ellipsoids at the
20% probability level. Final residuals: R1 = 0.0479, wR2 = 0.1374.13
η2,η3-cycloheptadienyl complex 2f (entry 11), respectively,
suggesting a much higher degree of reactivity for terminally
substituted pentadienyl systems.12
The reaction of 1-pentyne with pentadienyl complex 1a re-
quires heating at 40 °C, providing η5-cycloheptadienyl complex
3d in 91% yield as a 2:1 mixture of regioisomers (Table 1,
entry 4). The reaction with isosteric but electronically biased
ethoxyacetylene proceeds at a significantly accelerated rate
(entry 3), albeit with no improvement in regioselectivity. The
sterically differentiated terminal alkyne TMS-acetylene yields a
A DFT investigation of the reaction mechanism12 suggests
that the rate-limiting step of the cycloaddition process is alkyne
capture by dissociative interchange, forming cationic Cp*(η3-
pentadienyl)alkyne complex 6 (eq 6). The energy barrier
for complex formation is related to the dihedral angle between
the planes defined by the five carbon atoms of the open
pentadienyl ligand and the five carbon atoms of the ancillary
Cp*: the smaller the angle, the lower the TS energy barrier,
a
−
Table 2. CpCo(cycloheptadienyl)+BF4 Synthesis via [5 + 2] Cycloaddition
b
c
entry
substrate
7a (R1 = Me; R2, R3, R4 = H)
alkyne
8/yield (%)
8a/55
9/yield (%)
9a/99
1
2
3
4
R, R′ = H
R, R′ = Me
R, R′ = H
R, R′ = Me
7a
8b/43
8c/94
7b (R1 = TMS; R2, R3, R4 = H)
d
7b
8d + 9b (19:1)/68
9b: R1, R2, R3, R4 = H
8e/12
5
7c (R1 = Ph; R2, R3, R4 = H)
7c
7d (R1, R2, R3, R4, R5 = H)
R, R′ = H
R, R′ = Me
R, R′ = H
R, R′ = Me
R, R′ = Me
R, R′ = Me
R, R′ = Me
R, R′ = Me
6
8f + 9c (7:1)/63
8g + 9d (1:1.8)/47
7
e
e
8
7d
8h (1:2)
9e (1:3)/14
9
7e (R2 = Me; R1, R3, R4 = H)
7f (R3 = Me; R1, R2, R4 = H)
7g (R1, R2 = Me; R3, R4 = H)
7h (R1, R4 = Me; R2, R3 = H)
10
11
12
a
Detailed conditions are reported in the Supporting Information; yields of isolated products after SiO2 chromatography (3−4% MeOH in CH2Cl2)
b
c
are given. Conditions: ethyne (saturated solution in CH2Cl2), 40 °C, 72 h or 2-butyne (10 equiv), 40 °C, 72 h. As above, but 65−90 °C for 72 h.
d
e
The TMS group is cleaved under the conditions leading to η2,η3 → η5 isomerization.14 Formed as a mixture favoring an unidentified coproduct.
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cycloaddition reactions with 2-butyne. When TMS-substituted
7b is exposed to 2-butyne under the standard reaction
conditions, the major isolated product (19:1) is the η2,η3-
cycloheptadienyl isomer, despite the reaction being conducted
at 40 °C (Table 2, entry 4). For Ph-substituted 7c, the ratio of
η2,η3 to η5 isomers is 7:1 (entry 6); in contrast, the Cp*
analogue 2c shows significant isomerization even at room tem-
perature in CH2Cl2.15 DFT studies have suggested the lower
barrier to isomerization in the Cp* case is the result of in-
creased steric repulsion between the alkene substituents and
the methyl groups of the Cp* ancillary ligand, leading to facile
dissociation of the alkene prior to β-hydride elimination (2 → 5
in Scheme 3).12
The reduced cycloaddition reactivity of the Cp vs the Cp*
pentadienyl system is likely a result of differing steric effects.
Computations have indicated that steric repulsion between
the Cp* ancillary ligand and terminal pentadienyl substituents,
manifested as a decrease in the dihedral angle between the
pentadienyl planes, activates the system for cycloaddition
(vide supra).12 In the Cp system, the steric effects of the
ancillary ligand are significantly reduced, likely leading to a
larger dihedral angle and attenuated reactivity.
Preparation of Bicyclic Systems via Intramolecular
Cyclization. Preparation of Pentadienyl Complexes. Nucle-
ophilic addition to cationic metal species bearing unsaturated
ligands is well-known.16 We reasoned that an intramolecular
nucleophilic addition of a tethered latent nucleophile could be
used to prepare bicyclo[5.3.0] and bicyclo[5.4.0] systems from
the cationic η2,η3- and η5-cycloheptadienylcobalt complexes pre-
pared via [5 + 2] cycloaddition. To this end, we synthesized the
malonate-bearing pentadienol substrates 15 from the correspond-
ing dibrominated alkanes 10 (Scheme 4). The α,ω-bromoalkenes
with angles of ca. 7.5° or less providing optimal reactivity. Only
small deviations from coplanarity result from steric repulsions
between the terminal (1 and 5) substituents and the ancillary
ligand, but internal substituents serve to significantly raise the
dihedral angle. Complexes with smaller dihedral angles are
higher in energy and lie on the pathway for η5 → η3 isomeriza-
tion of the pentadienyl ligand leading to alkyne capture (eq 6).
CpCo(η5-pentadienyl)/Alkyne [5 + 2] Cycloaddition.
To explore the effects of the ancillary ligand on the [5 + 2]
cycloaddition reaction (eq 7 in Table 2), we prepared a series of
CpCo(η5-pentadienyl)+ complexes 7 (Table 2). Significantly
reduced yields in comparison with the Cp* series were ob-
tained in almost all cases; the primary exception to this trend is
that of unsubstituted complex 7d (Table 2, entries 7 and 8).
The structure of 7-methyl-η2,η3-cycloheptadienyl complex 7a
was unambiguously confirmed by X-ray diffraction (Figure 3).
Scheme 4. Preparation of Malonyl 1,3-Pentadienol
Substrates (15)
Figure 3. X-ray structure diagram for [CpCo(η2,η3-1-methylcyclo-
−
heptadienyl)]+BF4 (8a), with non-hydrogen atoms represented by
thermal ellipsoids at the 20% probability level. Final residuals: R1 =
0.0336, wR2 = 0.0870.13
For cycloadditions with ethyne to proceed, the reaction mixture
must be heated to 40 °C. Little to no reaction is observed at
room temperature; in contrast, the Cp* analogues are reactive
at room temperature and the reactions proceed to give excellent
yields. In several cases, the cycloaddition reactions do not pro-
ceed to completion after 3 days at 40 °C, even for pentadienyl
ligands known to be highly reactive such as Cp* analogues.
Despite the generally reduced reactivity of the CpCo(η5-
pentadienyl)+ complexes, unsubstituted complex 7d is un-
expectedly more reactive, giving a moderate yield of the
inseparable η2,η3- and η5-cycloheptadienyl complexes 8d (17%)
and 9b, respectively (30%, entry 7). This result is particularly
surprising in comparison to the complete lack of reactivity
observed for the unsubstituted Cp* analogue 1f (Table 1,
entry 12). Complex 7d is also reactive toward 2-butyne,
providing the η2,η3-cycloheptadienyl adduct 8h as a minor
product in combination with an unidentified major product
(entry 8). The nonconjugated η2,η3-cycloheptadienyl complexes
cleanly isomerize to the η5 isomers upon heating at 65 °C.
It is striking that the CpCo(η2,η3-cycloheptadienyl)+ isomers
display a higher degree of thermal stability than the Cp*
analogues, resisting η2,η3 → η5 isomerization during [5 + 2]
11 were prepared by “flash pyrolysis” in HMPA in acceptable
yields (32 and 54%, n = 1, 2, respectively).17 The malonate
nucleophile was installed by using dimethyl malonate in
THF/DMF (84 and 85%).18 Cross metathesis of diester 12
with crotonaldehyde using Grubbs’ second-generation catalyst
yields aldehydes 13 and 14.19 The use of 3 equiv of croton-
aldehyde is required to drive the reaction to completion; in the
absence of excess crotonaldehyde, significant amounts of
pseudodimerized 12 are observed after 16 h. Use of acrolein
in place of crotonaldehyde gave reduced yields due to catalyst
poisoning, indicated by a significant amount of undimerized 12
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in the 1H NMR spectrum of the crude reaction product.
Whether this poisoning is due to the acrolein itself or an
impurity was not investigated. Finally, addition of 2 equiv of
vinylmagnesium bromide yields the nonconjugated 1,4-
pentadienols 15 in reasonable to good yields (60 and 80%).
Attempted purification of aldehyde 14 by silica gel chromatog-
raphy leads instead to an intramolecular Michael addition
(eq 8) generating cyclic aldehyde 16, an undesired reaction that
spectrum of chromatography-purified material exhibiting para-
magnetic impurities. Complex 22 also decomposes slowly in
solution during crystallization and in the solid state at low
temperature in air. Such sensitivity was not observed for any
other Co(III) η5-pentadienyl complex we have prepared. We
tentatively ascribe this sensitivity to spontaneous intramolecular
cyclization, analogous to that observed for noncomplexed enal
14. An attempt to deliberately prepare such a cyclization prod-
uct via deprotonation with Hunig’s base under argon resulted in
̈
a complex mixture and was not further explored.
Acetal-protected pentadienol 20 was loaded onto the metal
under the same low-temperature protonolysis conditions
described previously (Scheme 7). With this method, the
also occurs slowly under the metathesis reaction conditions. As
a consequence, enal 14 was carried forward to dienol 15
without purification.
Scheme 7. Preparation and [5 + 2] Cycloaddition Reactions
of Ketone Substituted Pentadienyl Complex 30
The tethered pronucleophile was varied by introduction of a
masked ketone functionality (20) (Scheme 5). Acid-catalyzed
Scheme 5. Preparation of Masked Ketone Containing 1,3-
Pentadienol 20
acetal formation under Dean−Stark conditions converts
1-hexen-5-one (17) into the protected alkene 18.20 Ruthenium-
catalyzed cross metathesis and vinylmagnesium bromide
addition, as described, complete the synthesis. We did not
attempt unmasking of the ketone due to the possibility of a
competing Nazarov cyclization,21 opting instead to load acetal
20 directly onto the metal.
Both malonyl pentadienols 15 convert to cobalt pentadienyl
complexes in good yields under the standard reaction con-
ditions (Scheme 6). Pentadienylcobalt complex 21 was readily
protected pentadienyl complex 29 is obtained exclusively; the
acetal functionality is stable under the reaction conditions and
to silica gel chromatography but does hydrolyze slowly during
slow crystallization from (presumably wet) CH2Cl2/Et2O. The
protecting group can be removed without competitive cycliza-
tion using catalytic HBF4·OEt2 in wet acetone at reflux to yield
ketone-substituted pentadienyl complex 30 in 81% yield. The
structure was confirmed by X-ray diffraction (Figure 4).
Tethered Substrates: [5 + 2] Cycloaddition. Malonyl-tethered
pentadienyl complexes 21 and 22 both undergo clean cyclo-
addition in the presence of excess ethyne to yield η2,η3-
cycloheptadienyl complexes 23 and 24 in 89 and 81% yields,
respectively (Scheme 6). Complex 24, bearing the three-carbon
tether, was unambiguously characterized by X-ray crystallog-
raphy (Figure 5); no decomposition of this material is ob-
served, suggesting that the intramolecular nucleophilic
cyclization is not competitive with the cycloaddition, in con-
trast to the case for the open pentadienyl complex 22 and
organic enal 14. Isomerizations of 23 and 24 to the thermo-
dynamically favored η5-cycloheptadienyl complexes 25 and 26
also proceed smoothly at 60 °C.22 The cycloaddition reactions
with 2-butyne also proceed in good to excellent yields, providing
η5-1,2-dimethylcycloheptadienyl complexes 27 (70%) and 28
(93%), respectively.
Scheme 6. Preparation and [5 + 2] Cycloaddition Reactions
of Substituted Pentadienyls 21 and 22
The cycloaddition of η5-pentadienyl ketone complex 30
(Scheme 7) with ethyne leads cleanly to η2,η3-cycloheptadienyl
complex 31, with subsequent thermal isomerization to η5-
cycloheptadienyl complex 32 also proceeding cleanly in
purified and characterized. The homologous complex 22,
1
however, could not be rigorously purified, with the H NMR
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Figure 4. X-ray structure diagram for [Cp*Co(η5-1-(2-butanoyl)-
−
pentadienyl)]+BF4 (30), with non-hydrogen atoms represented by
thermal ellipsoids at the 20% probability level. Final residuals: R1 =
0.0363, wR2 = 0.0953.13
Figure 7. X-ray structure diagram for [Cp*Co(η5-cycloheptadie-
−
nyl)]+BF4 (32), with non-hydrogen atoms represented by thermal
ellipsoids at the 20% probability level. Final residuals: R1 = 0.0361,
wR2 = 0.0961.13
experiments, this material was obtained in approximately 10%
yield. Qualitative observations made over a series of experi-
ments suggest that higher concentrations of 2-butyne minimize
or eliminate the formation of this byproduct, although no
rationale can be offered for this effect.
The η5-pentadienyl acetal 29 also yields the expected η2,η3-
cycloheptadienyl complex 34 upon reaction with ethyne
(Scheme 8), as characterized by X-ray crystallography (Figure 8).
Figure 5. X-ray structure diagram for [Cp*Co(η2,η3-cycloheptadienyl)]+BF4−
(24), with non-hydrogen atoms represented by thermal ellipsoids at the
20% probability level. Final residuals: R1 = 0.0549, wR2 = 0.1584.13
Scheme 8. [5 + 2] Cycloaddition Reactions of Acetal-
Protected Pentadienyl Complex 29
excellent yield. Cycloheptadienyl complexes 31 and 32
were both crystallographically characterized, as illustrated in
Figures 6 and 7. The X-ray structure of η5-pentadienyl ketone
Figure 6. X-ray structure diagram for [Cp*Co(η2,η3-cycloheptadienyl)]+BF4−
(31), with non-hydrogen atoms represented by thermal ellipsoids at the
20% probability level. Final residuals: R1 = 0.0613, wR2 = 0.1641.13
complex 30 displays a dihedral angle of 7.40°, which supports
our structure/reactivity model.12 The corresponding cyclo-
addition with 2-butyne, however, does not consistently return
spectroscopically homogeneous η5-cycloheptadienyl ketone
complex 33. The byproduct is tentatively assigned as a co-
baltocenium complex believed to arise via competitive [3 + 2]
cycloaddition of the η3-pentadienyl intermediate, on the basis of
the characteristically small geminal coupling constants observed
in the 1H NMR spectra of cyclopentadienyl derivatives. In most
Figure 8. X-ray structure diagram for [Cp*Co(η2,η3-cycloheptadie-
−
nyl)]+BF4 (34), with non-hydrogen atoms represented by thermal
ellipsoids at the 20% probability level. Final residuals: R1 = 0.0582,
wR2 = 0.1601.13
However, the thermal η2,η3 → η5 isomerization to produce
complex 35, also unambiguously characterized by X-ray diffrac-
tion (Figure 9), is accompanied by partial acetal hydrolysis,
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conjugated product 38 is obtained exclusively in high yield.
Importantly, the cyclization proceeds with complete diaster-
eoselectivity, leading to the trans-fused bicyclic system
exclusively.
Surprisingly, cyclization of the three-carbon-tethered com-
plex 24 proceeds smoothly upon treatment with NaOMe in
MeCN, providing only the 1,4-cycloheptadiene complex 39 in
76% yield, with no isomerization to the conjugated diene
system (eq 9). Hunig’s base was ineffective in inducing
̈
Figure 9. X-ray structure diagram for [Cp*Co(η5-cycloheptadien-
−
yl)]+BF4 (35), with non-hydrogen atoms represented by thermal
ellipsoids at the 20% probability level. Final residuals: R1 = 0.0436,
cyclization. The thermal stability of bicyclic complexes 37 and
39 differs significantlybicyclo[5.4.0] complex 39 is indef-
initely stable in the solid state at −35 °C under a nitrogen
atmosphere, while the bicyclo[5.3.0] system 37 slowly
decomposes under identical conditions. 1H NMR spectroscopy
of the decomposition products suggests that reopening of the
five-membered ring is relatively facile in solution, presumably
by reionization of the tether. This process can be avoided by
prompt demetalation (vide infra) and has not been investigated
further.
The 2-butyne cycloadducts 27 and 28 were constructed with
the goal of introducing quaternary centers into the bicyclic sys-
tem upon nucleophilic cyclization. Using the NaOMe/MeCN
cyclization conditions, both 27 and 28 returned mixtures of two
products in a 2:1 ratio, as revealed by 1H NMR spectroscopy of
the isolated crude products. The major product is the desired
bicyclic complex 40, accompanied by a species tentatively
assigned as cycloheptatriene complex 41, arising from com-
petitive deprotonation of the terminal methyl group (eq 10).
wR2 = 0.1189.13
which also occurs slowly during crystallization at room tem-
perature. A similar competitive deprotection occurs during the
cycloaddition of 2-butyne at 40 °C. Cyclic acetals are generally
stable under neutral conditions, but it is possible that the
Co(III) complex itself functions as a Lewis or Brønsted acid,
resulting in competitive acetal hydrolysis by adventitious water
at elevated temperature. Acid-catalyzed hydrolysis of both the
η2,η3- and η5-cycloheptadienyl acetal complexes 34 and 35
leads to η5-cycloheptadienyl complex 32, identical with that
obtained via direct treatment of η5-pentadienyl ketone complex
30 with ethyne followed by isomerization. Since acetal cleavage
and η2,η3 → η5 isomerization can be achieved in one pot, the
transformation of acetal complex 29 to ketone cycloheptadienyl
complex 32 can be conducted conveniently as a one-step
procedure.
Intramolecular Cyclization. With cyclopheptadienyl com-
plexes 23, 24, 27, 28, and 31−33 in hand, we turned our
attention to the formation of bicyclic adducts via intramolecular
nucleophilic addition. Initial attempts to deprotonate η2,η3-
cycloheptadienyl complexes 23 and 24 were performed using
NaOMe in MeCN at room temperature. The 1H NMR spectra
of the crude bicyclic reaction product contained significant
impurities. The use of Hunig’s base in THF at −78 °C reduced
̈
these side reactions, but the process unfortunately also proved
to be irreproducible. Ultimately, we settled on the use of
K2CO3 suspended in MeOH at room temperature as optimal
(Scheme 9), returning a 77% yield of cyclization products, but
Upon heating in benzene-d6 at 70 °C for 16 h, the crude
product mixture equilibrates to a 1:5 ratio, now favoring the
undesired exocyclic cycloheptatriene 41. A reasonable equi-
libration mechanism invokes a reversible kinetic cyclization/
reionization to the bicyclic complex 40 proceeding more slowly
than deprotonation to give the thermodynamically favored
triene 41.
Scheme 9. Cyclization of Cycloheptadienyl Complex 23
Equilibration of the kinetic cyclization product should be
less favorable in the ketone enolate systems generated by
deprotonation of complexes 31−33. The use of the standard
kinetic base LDA led to complex product mixtures, likely due to
competing deprotonation of the allylic ring protons or a single-
electron-transfer cascade. These difficulties were circumvented
classically, by generating enamine intermediates23 using
pyrrolidine.24 Treatment of η5-ketone complex 32 with a
stoichiometric amount of pyrrolidine in wet methanol leads
to bicyclic 1,3-cycloheptadiene complex 42 in moderate yield,
as an unselective 2:1 mixture of the anticipated 1,4-cyclo-
heptadiene complex 37 and the isomerized 1,3-cycloheptadiene
complex 38. Using K2CO3 in wet MeOH, however, the
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Scheme 10. Alternate Cyclization Mechanisms Leading to
Bicyclic Isomers 42 and 43
isolated as a spectroscopically pure compound after filtration
through Celite under nitrogen (eq 11). Hydrolysis of the
putative iminium intermediate occurs in situ; when rigorously
dried MeOH is used as the reaction solvent, no cyclization
products are obtained. The trans ring fusion was unambigu-
ously determined through single-crystal X-ray diffraction
(Figure 10).
spectroscopically analogous to that of the crystallographically
characterized complex 42.
Decomplexation of Co(I) Cycloheptadiene Cycloadducts.
The stereoselective synthesis of bicyclic cycloheptadiene com-
pounds is completed by decomplexation to give the metal-free
organic product. Standard methods, such as one- or two-
electron oxidation using ferrocenium salts in biphasic pentane/
MeCN,8b are productive but low-yielding. To improve the
decomplexation yield and enable recyclability of the metal, we
report a novel allylative demetalation procedure, potentially
applicable to other demetalation-resistant cobalt diene systems.
In the presence of allyl bromide under UV photochemical
irradiation,26 Cp*Co(cycloheptadiene) complexes are cleanly
converted to Cp*Co(η3-allyl)Br27 with near-quantitative
liberation of the intact cycloheptadiene ligand. The reaction
is successful for both conjugated and nonconjugated diene
complexes. Photolysis of the conjugated [5.3.0] complex 38 in
the presence of excess allyl bromide, for example, provides an
excellent yield of trans-hexahydroazulene 47 with complete
retention of the ring fusion and diene position (eq 14). In
Figure 10. X-ray structure diagram for [Cp*Co(η4-[5.4.0]-bicycloun-
−
decadienone)]+BF4 (42), with non-hydrogen atoms represented by
thermal ellipsoids at the 20% probability level. Final residuals: R1 =
0.0294, wR2 = 0.0778.13
Exposure of η2,η3-cycloheptadienyl complex 31 to the same
pyrrolidine-mediated conditions produces a 4:1 mixture of the
desired 1,4-cycloheptadiene complex 43 accompanied by minor
amounts of the conjugated 1,3-diene complex 42 (eq 12). The
absence of strong base in this reaction suggests that competitive
deprotonation/reprotonation is not likely to induce diene iso-
merization. We suggest, however, that the cyclization reaction
proceeds via competitive kinetic alkylation at two electrophilic
sites: the η3-allyl moiety, leading directly to the nonconjugated
product 43, and the η2-olefin, in accordance with the Davies−
Green−Mingos selectivity rules (Scheme 10).25 The latter gives
rise to the η1:η3 intermediate 44, which can undergo β-hydride
elimination/reinsertion, resulting in the conjugated product 42.
It is conceivable that such a pathway is also at play in the
formation of malonyl adducts 37 and 38 (Scheme 9). Such
mechanistic ambiguities remain under investigation.
addition to the liberated organic, Cp*Co(η3-allyl)Br is isolated
as a red solid in moderate yield via silica gel chromatography,
opening up the possibility for recycling of the metal reagent.
Under the same conditions, decomplexation of the non-
conjugated diene complex 39 returns an 85% yield of
bicyclo[5.4.0]undecadiene 48, again with complete retention
of geometric and structural features (eq 15). Unfortunately,
Upon exposure of 2-butyne cycloadduct 33 to pyrrolidine,
the expected bicyclic complex 46 is obtained in a reasonable
65% yield (eq 13). The angular methyl substituent at the qua-
ternary stereocenter is produced as a single diastereoisomer,
and the ring fusion is tentatively assigned as trans and is
photochemical decomplexation of the mixture of complexes 37
and 38 results in a mixture of two organic products; the minor
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“reaction bomb” and “bomb” refer to a thick-walled glass vessel with a
Teflon stopcock capable of withstanding moderately elevated internal
pressure.
component is tentatively assigned as the desired nonconjugated
bicycle, while the major component in the mixture could not be
identified. The H NMR spectrum of the crude product mix-
1
IR spectra were recorded on either a Nicolet Magna 750 FTIR
spectrometer or a Nic-Plan FTIR microscope. 1H NMR and 13C NMR
spectra were recorded on a Varian Unity-Inova 300 (1H, 300 MHz),
Varian Unity-Inova 400 (1H, 400 MHz; 13C, 100 MHz), Varian
Mercury 400 (1H, 400 MHz; 13C, 100 MHz), Varian Unity-Inova 500
(1H, 500 MHz; 13C, 125 MHz), Varian DirectDrive 500 (1H, 500
MHz; 13C, 125 MHz), or Varian Unity-Inova 600 (1H, 600 MHz)
spectrometer. High-resolution mass spectra, performed by the
University of Alberta Mass Spectrometry Facility, were obtained on
an Applied Biosystems Mariner Biospectrometry Workstation (electro-
spray ionization) or a Kratos Analytical MS-50G workstation (electron
impact ionization) with an ionization energy of 70 eV. Elemental
analyses were performed by the University of Alberta Microanalysis
Laboratories, using a Carlos Erba Instruments CHSN-O EA1108
Elemental Analyzer. X-ray diffraction data were recorded on a Bruker
Platform diffractometer with a SMART 1000 CCD area detector at
−80 °C. Data collection, structure solution, and refinements were
performed by Drs. Robert McDonald and Michael J. Ferguson of the
University of Alberta X-ray Crystallography Laboratory. Crystals
suitable for X-ray crystallography were often grown with a technique
herein referred to as “two-chambered liquid diffusion”. In this method,
a small quantity of material was dissolved in a single solvent and
placed in a small glass crystallization tube, which was then topped
up with additional solvent if needed. The tube was sealed with an
NMR-tube cap that was perforated once with a narrow-gauge needle.
This tube was placed in a large sample vial and immersed in a second
solvent in which the complex has minimal solubility. Due to the very
slow diffusion rate via the pinhole, several weeks may be required
to achieve complete crystallization. 1H NMR chemical shifts are
reported relative to residual protiated solvent. 13C NMR chemical
shifts are reported relative to the deuterated solvent. All spectra were
recorded at 27 °C. Values of the coupling constants were obtained
directly from the spectrum. GCOSY denotes the standard COSY
experiment, acquired using field gradients. Data for the 1H−1H
COSY or GCOSY are presented such that correlations are listed only
once.
ture displays signals reminiscent of the monocyclic organo-
metallic precursor 23, suggesting that this product derives
from an oxidatively induced ring-opening process. The use of
alternate decomplexation conditions, including ferrocenium
oxidation or iodinolysis, resulted in similar complex product
mixtures.
Photolytic decomplexations of the ketone-containing bicyclic
complexes 42 and 46 proceed quantitatively; bicyclic ketones
49 and 50 were isolated as pure materials in 96% and 95%
yields, respectively (eq 16). No loss of stereochemical or com-
positional integrity was detected in either system.
CONCLUSION
■
While still an underexplored reaction, the metal-mediated
[5 + 2] cycloaddition manifold is becoming increasingly utilized
by the synthetic community.3 Here we have established the
synthetic scope of the cobalt-mediated pentadienyl/alkyne
[5 + 2] cycloaddition reaction. Both Cp*- and CpCo-
(pentadienyl)+ complexes undergo selective single insertion/
cyclization upon reaction with alkynes. In comparison to the
more general Cp* system, the CpCo(η2,η3-cycloheptadienyl)+
complexes are obtained in reduced yields but show a higher
barrier to η2,η3 → η5 isomerization of the seven-membered
ring. While the substituent scope remains modest, limited to
substituents at the 1- and 5-positions of the pentadienyl frag-
ment, metal-directed intramolecular cyclization of tethered
nucleophiles postcycloaddition leads to an efficient synthesis of
bicyclic organic products of reasonable structural complexity,
with complete diastereocontrol. The process can be used to
introduce quaternary stereocenters in high selectivity. From a
more general perspective, the novel photolytic oxidative de-
complexation addresses a longstanding problem in synthetic
organocobalt chemistry, offering improved prospects for
applications of Co(III)-mediated cycloaddition reactions to
complex molecule synthesis.
Materials. Compounds prepared by published procedures are as
follows: pentadienyl complexes 1a−k and 7a−h,6 Cp*Co(CH2CH2)2
(4),28 1-bromo-3-butene and 1-bromo-4-pentene (11),17 methyl pent-1-
ene-5-methylcarboxyloate and methyl hex-1-ene-6-methylcarboxyloate
(12),18 enal 13,22 5-hexen-2-one cyclic 1,2-ethandiyl acetal (18).20
Cp*Co(η2,η3-4-methylcycloheptadienyl)+PF6− (2a). A test tube
was charged with a solution of pentadienyl 1a (39.5 mg, 0.0940 mmol)
in freshly distilled dichloromethane (10 mL). The tube was fitted with
a septum, and acetylene was streamed through the solution for ∼15 min,
to ensure saturation. The solution was maintained at room tem-
perature for 19 h, before the removal of solvent by rotary evaporation.
The orange-red residue was chromatographed on silica gel with a 4%
methanol in dichloromethane mixture, affording 2a as a red solid
(41.3 mg, 0.0925 mmol, 98%). A small amount of 2a suitable for X-ray
diffraction analysis was obtained by crystallization by pinhole diffusion
from a 50:50 mixture of diethyl ether and dichloromethane. IR
(microscope, cm−1): 2974 (w), 2920 (w), 2876 (m), 1711 (s), 1575
(s), 1502 (w), 1470 (w), 1434 (w), 1381 (w), 1337 (s), 1303 (m),
1285 (m), 1262 (m), 1184 (s), 1161 (s), 1141 (s), 1113 (s), 1075
(m), 1027 (w), 987 (m), 967 (m), 912 (m), 845 (w), 796 (w), 740
EXPERIMENTAL SECTION
■
General Experimental Procedures. All manipulations of air-
sensitive compounds were performed under an argon or nitrogen
atmosphere using standard Schlenk techniques or in an MBraun
LABmaster sp drybox. Diethyl ether and tetrahydrofuran were distilled
from sodium/benzophenone ketyl under nitrogen. Pentane was
distilled from potassium/benzophenone ketyl under nitrogen.
Dichloromethane and acetonitrile were distilled from calcium hydride
and degassed. Acetone was dried over boric oxide, degassed via three
freeze−pump−thaw cycles, vacuum-transferred, and stored under
nitrogen. All other reagents were used without further purification.
Flash column chromatography was performed with Silicycle silica gel
(40−63 μm), neutralized with 1 mL of triethylamine for acid-sensitive
compounds. Alumina filtrations were performed with Sigma-Aldrich
neutral aluminum oxide, Brockman I, standard grade, 150 mesh, 58 Å,
deactivated to Activity IV with 10 wt % water. Photolysis reactions
were performed with a Hanovia 450 W high-pressure mercury lamp
filtered through Pyrex or a Rayonette UV reaction carousel. The terms
1
(m). H NMR (500 MHz, dichloromethane-d2): δ 3.85 (app td, 1H,
J1−2 = 7.6 Hz, J1−7eq = 8.5 Hz, J1−7ax = 4.2 Hz, H1), 3.55 (dd, 1H, J2−3
=
7.6 Hz, J3−4 = 3.7 Hz, H3), 3.22 (t, 1H, J1−2 = J2−3 = 7.6 Hz, H2), 3.06
(ddd, 1H, J7ax−7eq = 14.2 Hz, J1−7eq = 8.5 Hz, J6−7eq = 8.3 Hz, H7eq),
2.77 (ddd, 1H, J5−6 = 6.6 Hz, J6−7eq = 8.3 Hz, J6−7ax = 4.7 Hz, H6), 2.40
(m, 1H, H4), 2.35 (dd, 1H, J5−6 = 6.6 Hz, H4−5 = 5.0 Hz, H5), 2.17 (dt,
1H, J7ax−7eq = 14.2 Hz, J6−7ax = 4.7 Hz, J1−7ax = 4.2 Hz, H7ax), 1.82 (s,
15H, CpMe5), 1.47 (d, 3H, J4−CH = 6.9 Hz, H4−CH3). 13C NMR
3
(125 MHz, dichloromethane-d2): δ 98.1 (C5Me5), 92.5 (C2), 55.9
(C5), 52.4 (C3), 46.0 (C6), 44.4 (C1), 27.3 (C4), 22.1 (C7), 19.7 (C4−CH3),
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9.9 (C5Me5). HMQC (500 MHz, dichloromethane-d2): δ 92.5 ↔ δ 3.22; δ
55.9 ↔ δ 2.35; δ 52.4 ↔ δ 3.55; δ 46.0 ↔ δ 2.77; δ 44.4 ↔ δ 3.85;
δ 27.3 ↔ δ 2.40; δ 22.1 ↔ δ 3.06, δ 2.17; δ 19.7 ↔ δ 1.47; δ 9.9 ↔
δ 1.82. HMBC (500 MHz, dichloromethane-d2): δ 92.5 ↔ δ 3.06;
δ 55.9 ↔ δ 3.06, δ 1.47; δ 52.4 ↔ δ 1.47; δ 46.0 ↔ δ 3.06, δ 2.35, δ
2.17; δ 44.4 ↔ δ 3.55, δ 3.22, δ 3.06, δ 2.17; δ 27.3 ↔ δ 3.22, δ
2.77, δ 1.47; δ 22.1 ↔ δ 3.22, δ 2.77, δ 2.35; δ 19.7 ↔ δ 2.35. Anal.
Calcd for C18H26CoPF6: C, 48.44; H, 5.87. Found: C, 48.18; H,
5.91.
H5), 2.19 (app dt, 1H, JH1−H7ax = 4.2 Hz, JH7ax−H7eq = 14.2 Hz,
JH6−H7ax = 4.7 Hz, H7ax), 2.16 (m, 1H, H4), 1.85 (m, 2H, -CH2CH3),
1.81 (s, 15H, CpMe5), 1.04 (t, 3H, JCH ‑CH = 7.4 Hz, −CH2CH3).
2
3
1H−1H GCOSY (500 MHz, dichloromethane-d2) δ 3.84 ↔ δ 3.23, δ
3.07, δ 2.19; δ 3.61 ↔ δ 3.23, δ 2.16; δ 3.23 ↔ δ 2.19; δ 3.07 ↔ δ 2.79,
δ 2.39, δ 2.19; δ 2.79 ↔ δ 2.39, δ 2.19; δ 2.39 ↔ δ 2.16; δ 2.16 ↔ δ
1.85; δ 1.85 ↔ δ 1.04; 13C NMR (100 MHz, dichloromethane-d2): δ
98.1 (C5Me5), 92.5 (C2), 54.7 (C5), 50.9 (C3), 46.2 (C6), 44.5 (C1),
34.1 (C4), 27.5 (-CH2CH3), 22.1 (C7), 10.9 (−CH2CH3), 9.9
(C5Me5). HMQC (400 MHz, dichloromethane-d2): δ 92.5 ↔ δ
3.23; δ 54.7 ↔ δ 2.39; δ 50.9 ↔ δ 3.61; δ 46.2 ↔ δ 2.79; δ 44.5 ↔ δ
3.84; δ 27.5 ↔ δ 1.85; δ 22.1 ↔ δ 3.07, δ 2.19; δ 10.9 ↔ δ 1.04;
δ 9.9 ↔ δ 1.81. HMBC (500 MHz, dichloromethane-d2): δ 98.1 ↔ δ
1.81; δ 92.5 ↔ δ 3.07; δ 54.7 ↔ δ 3.07, δ 2.79, δ 1.85; δ 50.9 ↔ δ 3.84,
δ 3.23, δ 1.85; δ 46.2 ↔ δ 3.07, δ 2.39, δ 2.19; δ 44.5 ↔ δ 3.61, δ 3.23,
δ 3.07; δ 27.5 ↔ δ 3.61, δ 2.39, δ 1.04; δ 22.1 ↔ δ 3.23, δ 2.79, δ 2.39;
δ 10.9 ↔ δ 1.85. Anal. Calcd for C19H28CoPF6: C, 49.58; H, 6.13.
Found: C, 49.47; H, 5.98.
−
[Cp*Co(η2,η3-1-phenylcycloheptadienyl)]+BF4 (2c). [Cp*Co-
−
(η5-1-phenylpentadienyl)]+ BF4 (16 mg, 0.038 mmol) was dissolved
in CH2Cl2 (3 mL) and degassed with argon for 5 min. Simultaneously,
acetylene was bubbled through CH2Cl2 in a test tube for 25 min in
order to ensure saturation. Then, 2 mL of this saturated solution was
transferred to the bomb via cannula. The bomb was sealed and allowed
to stand at room temperature overnight. During this time, the color
was seen to change gradually from dark red to orange-red. The solvent
was then removed in vacuo and the product purified by silica gel
chromatography using 3% MeOH/CH2Cl2. The red fraction was
collected and dried, providing 15 mg (89%) of product as a thick, red
−
[Cp*Co(η2,η3-1,5-dimethylcycloheptadienyl)]+BF4 (2e).
−
[Cp*Co(η5-1,5-dimethylpentadienyl)]+BF4 (11 mg, 0.029 mmol)
1
oil. The H NMR spectrum showed that there was a small quantity
was dissolved in CH2Cl2 (3 mL) and degassed with argon for 5 min.
Simultaneously, acetylene was bubbled through CH2Cl2 in a test tube
for 25 min in order to ensure saturation. Then, 2 mL of this saturated
solution was transferred to the bomb via cannula. The bomb was
sealed and allowed to stand at room temperature for 3 days. The
solvent was removed in vacuo and the product purified by silica gel
chromatography using 3% MeOH/CH2Cl2. The red fraction was
collected and dried, providing 11 mg (94%) of product as a thick, red
oil. Crystallization via two-chambered liquid diffusion using CH2Cl2
and Et2O provided red crystals suitable for combustion and X-ray
analysis. IR (neat, cm−1): 2978 (w), 2930 (w), 2878 (w), 1460 (w),
1429 (w), 1383 (m), 1313 (w), 1283 (w), 1263 (w), 1050 (s), 1036
(s), 988 (w), 900 (w), 864 (w), 803 (w). 1H NMR (400 MHz,
CDCl3): δ 3.59 (dd, J2−1 = 7.6 Hz, J2−3 = 3.8 Hz, 2H, H2), 3.42 (tt,
J1−2 = 7.7 Hz, J1−3 = 0.7 Hz, 1H, H1), 2.38 (d, J4−3 = 3.2 Hz, 2H, H4),
2.34 (m, 2H, H3), 1.87 (s, 15H, C5Me5), 1.47 (d, JMe‑3 = 6.8 Hz, 6H,
(ca. 10%) of the fully conjugated isomer present. Since the product
slowly isomerizes at room temperature, only spectroscopic character-
ization was obtained. IR (neat, cm−1): 3639 (w), 3552 (w), 3061 (s),
3032 (s), 2964 (s), 2916 (s), 2861 (s), 2262 (s), 1817 (w), 1603 (s),
1552 (w), 1494 (s), 1453 (s), 1430 (s), 1384 (s), 1286 (s), 1184 (w),
1097 (s), 916 (s), 830 (w), 794 (w), 761 (s), 734 (s), 702 (s). H
NMR (400 MHz, CDCl3): δ 7.51−7.34 (m, 5H, Ph, overlaps solvent
signal), 4.10 (dd, J1−2 = 7.3 Hz, J1−7 = 4.0 Hz, 1H, H1), 4.06 (td,
1
J3−4endo = J3−2 = 8.2 Hz, J3−4exo = 4.1 Hz, 1H, H3), 3.51 (t, J2−1 = J2−3
=
7.7 Hz, 1H, H2), 3.40 (t, J7−1 = J7−6 = 4.2 Hz, 1H, H7), 3.30 (dt,
J4endo−4exo = 14.1 Hz, J4endo−3 = J4endo−‑5 = 8.6 Hz, 1H, H4endo), 3.02 (td,
J5−4endo = J5−6 = 7.5 Hz, J5−4exo = 4.8 Hz, 1H, H5), 2.75 (td, J6−5
J6−7 = 6.0 Hz, J6−4exo = 0.3 Hz, 1H, H6), 2.31 (br app dt, J4exo−4endo
=
=
13.9 Hz, J4exo−3 = J4exo−5 = 4.4 Hz, 1H, H4exo), 1.84 (s, 15H, C5Me5).
1H−1H GCOSY (400 MHz, CDCl3): δ 4.10 (H1) ↔ δ 3.51 (H2), 3.40
(H7); δ 4.06 (H3) ↔ δ 3.51 (H2), 3.30 (H4endo), 2.31 (H4exo); δ 3.51
(H2) ↔ δ 3.30 (H4endo), 2.31 (H4exo); δ 3.40 (H7) ↔ δ 2.75 (H6), 2.31
(H4exo); δ 3.30 (H4endo) ↔ δ 3.02 (H5), 2.75 (H6), 2.31 (H4exo); δ 3.02
(H5) ↔ δ 2.75 (H6), 2.31 (H4exo); δ 2.75 (H6) ↔ δ 2.31 (H4exo).
13C{1H} NMR (100 MHz, CDCl3): δ 139.4, 129.4, 128.9, 128.0,
126.5, 98.0, 91.7, 48.7, 45.7, 45.5, 36.2, 21.7, 9.7. Electrospray MS:
m/z calculated for C23H28Co (M+ − BF4) 363.15175, found
363.15182 (100%).
1
Me). H−1H GCOSY (400 MHz, CDCl3): δ 3.59 (H2) ↔ δ 3.42
(H1), 2.34 (H3); δ 3.42 (H1) ↔ δ 2.34 (H3); δ 2.38 (H4) ↔ δ 2.34
(H3); δ 2.34 (H3) ↔ δ 1.47 (Me). 13C{1H} NMR (100 MHz, CDCl3):
δ 98.1, 91.7, 54.2, 52.9, 27.8, 19.9, 10.2. Electrospray MS: m/z cal-
culated for C19H28Co (M+ − BF4) 315.15175, found 315.15156
(100%). Anal. Calcd for C19H28CoBF4: C, 56.74; H, 7.02. Found: C,
56.36, H, 7.33.
−
[Cp*Co(η2,η3-1,2,3,4-tetramethylcycloheptadienyl)]+BF4
−
Cp*Co(η2,η3-4-ethylcycloheptadienyl)+PF6 (2d). A test tube
(2f). [Cp*Co(η5-1,5-dimethylpentadienyl]+BF4− (80 mg, 0.213 mmol)
was dissolved in CH2Cl2 (15 mL) in a reaction bomb and degassed
with argon for 5 min. To this was added 2-butyne (80 μL, 1.02 mmol)
via syringe. The bomb was sealed and heated at 40 °C for 3 days in an
oil bath. The solvent was then removed in vacuo and the product
purified by silica gel chromatography using 3% MeOH/CH2Cl2. The
red fraction was collected and dried, providing 78 mg (85%) of
product as a thick, red oil. Crystallization attempts would lead only to
decomposition; thus, spectroscopic characterization alone was ob-
tained. IR (neat, cm−1): 3032 (w), 2966 (m), 2905 (m), 1473 (m),
1390 (m), 1329 (w), 1282 (w), 1259 (s), 1181 (w), 1044 (s), 901 (w),
861 (w), 799 (s). 1H NMR (400 MHz, CDCl3): δ 3.67 (dd, J2−1 = 7.4
Hz, J2−3 = 4.5 Hz, 2H, H2), 3.12 (t, J1−2 = 7.4 Hz, 1H, H1), 2.69 (qd,
J3−Me = 6.7 Hz, J3−2 = 4.4 Hz, 2H, H3), 1.73 (s, 15H, C5Me5), 1.72 (s,
was charged with a solution of 1d (47.9 mg, 0.127 mmol) in freshly
distilled dichloromethane (5 mL). The tube was fitted with a septum,
and acetylene was streamed through the solution for ∼15 min, to
ensure saturation. The solution was maintained at room tempera-
ture for 18 h, before the removal of solvent by rotary evaporation. The
orange-red residue was chromatographed on silica gel with a 4%
methanol in dichloromethane mixture, affording a red gum (46.6 mg,
−
0.116 mmol, 91%) which was comprised primarily of 2d as the BF4
1
salt but contained traces (less than 5% each by H NMR integration)
of minor impurities. The salt was completely dissolved in water
(∼3 mL) and treated with saturated aqueous KPF6 (5 mL). The red
precipitate was collected by filtration and chromatographed on silica
gel with a 4% methanol in dichloromethane mixture to furnish 2d as a
−
1
red powder (41.3 mg, 0.0897 mmol, 77% from BF4 salt). Crystals of
6H, Me), 1.46 (d, JMe‑3 = 7.1 Hz, 6H, Me). H−1H GCOSY (400
analytical purity suitable for an X-ray diffraction study were grown
from a 50:50 mixture of diethyl ether and dichloromethane at −80 °C.
IR (microscope, cm−1): 3003 (w), 2968 (m), 2928 (m), 2879 (w),
1470 (m), 1460 (m), 1388 (m), 1379 (m), 1308 (w), 1290 (w), 1236
(w), 1073 (w), 1028 (w), 991 (w), 940 (w), 907 (w), 891 (w), 877
(m), 843 (s), 806 (m), 777 (w). 1H NMR (400 MHz, dichloro-
MHz, CDCl3): δ 3.67 (H2) ↔ δ 3.12 (H1), 2.69 (H3); δ 3.12 (H1) ↔
δ 2.69 (H3); δ 2.69 (H3) ↔ δ 1.72 (Me), 1.46 (Me). 13C{1H} NMR
(100 MHz, CDCl3): δ 96.6, 89.6, 63.3, 52.1, 32.0, 18.5, 14.2, 9.5.
Electrospray MS: m/z calculated for C21H32Co (M+ − BF4): 343.18305,
found 343.18302 (100%).
−
Cp*Co(7-methylcycloheptadienyl)+PF6 (3a). An NMR tube
methane-d2): δ 3.84 (dtm, 1H, J1−2 = 7.6 Hz, J1−7eq = 8.4 Hz, J1−7ax
=
was charged with a solution of 2a (10.7 mg, 0.161 mmol, >95% pure)
in dichloromethane-d2 (∼750 μL). The tube was tightly sealed and
4.2 Hz, H1), 3.61 (dd, 1H, J2−3 = 7.6 Hz, J3−4 = 3.6 Hz, H3), 3.23 (tm,
1H, J1−H = J2−3 = 7.6 Hz, H2), 3.07 (dtm, 1H, J7ax−7eq = 14.2 Hz, J1−7eq
1
stored at room temperature for 4 days, at which point H NMR anal-
= 8.4 Hz, J6−7eq = 8.4 Hz, H7eq), 2.79 (dtapp, 1H, J5−6 = 6.6 Hz, J6−7eq
=
ysis revealed a 12% conversion of 2a to η5-cycloheptadienyl complex
3a. The NMR tube was then heated at 60 °C for 17 h, at which point
8.4 Hz, J6−7ax = 4.7 Hz, H6), 2.39 (dd, 1H, J5−6 = 6.6 Hz, J4−5 = 4.6 Hz,
3345
DOI: 10.1021/acs.organomet.5b00346
Organometallics 2015, 34, 3335−3357

Organometallics
Article
1
the conversion was determined by H NMR to be >98% complete.
Upon removal of solvent in vacuo, 3a (10.7 mg, 0.161 mmol, 100%,
>95% pure) was recovered as an orange-red solid. As complex 3a had
been previously prepared and characterized, no further purification or
characterization was undertaken.29
6.40 (tappd, 1H, J2−3 = 6.9 Hz, J3−4 = 7.6 Hz, J3−5 = 1.0 Hz, H3), 4.87
(d, 1H, J2−3 = 6.9 Hz, H2), 4.79 (ddm, 1H, J3−4 = 7.6 Hz, J4−5 = 6.4 Hz,
H4), 4.04 (tappdd, 1H, J4−5 = 6.4 Hz, J5−6ax = 8.0 Hz, J5−6eq = 4.7 Hz,
J3−5 = 1.0 Hz, H5), 1.95 (m, 1H, J5−6ax = 8.0 Hz, J6ax−6eq = 15.2 Hz,
H6ax), 1.77 (s, 15H, CpMe5), 1.67 (m, 1H, J7−CH = 6.8 Hz, H7), 1.40
3
Cp*Co(η5-1,2,7-trimethylcycloheptadienyl)+PF6 (3b). A glass
(t, 3H, J = 7.0 Hz, −OCH2CH3), 1.32 (td, 1H, J5−6eq = 4.7 Hz, J6eq−7 =
−
bomb was charged with a solution of 1a (67.8 mg, 0.161 mmol) in
dichloromethane (∼4 mL). Argon was streamed through the solu-
tion for several minutes, prior to the injection via syringe of 2-butyne
(75 μL, ∼0.96 mmol). The bomb was sealed, and the solution was
maintained at 42 °C for 72 h. The solvent was removed in vacuo, and
the red residue was chromatographed on silica gel with a 3%
methanol/dichloromethane eluent. The deep red fraction was
collected and, upon removal of solvent and subsequent drying under
high vacuum, analytically pure 3b (75.6 mg, 0.159 mmol, 99%) was
obtained. IR (microscope, cm−1): 2971 (s), 2912 (s), 2826 (s), 1675
(w), 1576 (w), 1436 (s), 1381 (s), 1325 (m), 1298 (m), 1230 (w),
1206 (w), 1195 (m), 1160 (w), 1118 (w), 1074 (m), 1029 (s), 961
(m), 933 (w), 904 (m), 874 (m), 843 (m), 776 (m), 740 (m), 677
4.7 Hz, J6ax−6eq = 15.2 Hz, H6eq), 1.17 (d, 3H, J7−CH = 6.8 Hz, C7−
3
CH3). 1H−1H GCOSY (400 MHz, chloroform-d): major isomer 3c, δ
6.24 ↔ δ 5.07, δ 3.75; δ 5.07 ↔ δ 4.31; δ 4.31 ↔ δ 2.03, δ 1.64; δ
4.12 ↔ δ 3.97, δ 1.40; δ 3.97 ↔ δ 1.40; δ 3.75 ↔ δ 1.11; δ 2.03 ↔ δ
1.64, δ 1.11; δ 1.64 ↔ δ 1.11; δ 1.15 ↔ δ 1.11. 1H−1H GCOSY (400
MHz, chloroform-d): minor isomer 3c′, δ 6.40 ↔ δ 4.87, δ 4.79; δ
4.79 ↔ δ 4.04; δ 4.04 ↔ δ 1.95, δ 1.32; δ 3.81 ↔ δ 3.79, δ 1.40; δ
3.79 ↔ δ 1.40; δ 1.95 ↔ δ 1.67, δ 1.32; δ 1.67 ↔ δ 1.32, δ 1.17; δ 1.32
↔ δ 1.17. 13C NMR (100 MHz, chloroform-d): major isomer 3c, δ
139.7 (C2), 98.3 (C5Me5), 94.8 (C4), 89.0 (C5), 84.8 (C3), 77.2 (C1),
67.3 (-OCH2CH3), 43.6 (C6), 36.1 (C7), 22.7 (C7−CH3), 14.5
(−OCH2CH3), 9.9 (C5Me5); 13C NMR (100 MHz, chloroform-d)
Minor Isomer 3c′: δ 151.2 (C1), 97.0 (C5Me5), 95.6 (C4), 91.8 (C3),
79.5 (C5), 78.2 (C2), 66.2 (-OCH2CH3), 42.4 (C7), 41.2 (C6), 18.2
(C7−CH3), 14.3 (−OCH2CH3), 9.4 (C5Me5); HMQC (400 MHz,
chloroform-d): major isomer 3c, δ 94.8 ↔ δ 5.07; δ 89.0 ↔ δ 4.31; δ
84.8 ↔ δ 6.24; δ 77.2 ↔ δ 3.75; δ 67.3 ↔ δ 4.12, δ 3.97; δ 43.6 ↔ δ
2.03, δ 1.64; δ 36.1 ↔ δ 1.11; δ 22.7 ↔ δ 1.15; δ 14.5 ↔ δ 1.40; δ
9.9 ↔ δ 1.82. HMQC (400 MHz, chloroform-d): minor isomer 3c′, δ
95.6 ↔ δ 4.79; δ 91.8 ↔ δ 6.40; δ 79.5 ↔ δ 4.04; δ 78.2 ↔ δ 4.87; δ
66.2 ↔ δ 3.81, δ 3.79; δ 42.9 ↔ δ 1.67; δ 41.2 ↔ δ 1.95, δ 1.32; δ 18.2
↔ δ 1.17; δ 14.3 ↔ δ 1.40; δ 9.4 ↔ δ 1.77. Electrospray high-
resolution mass spectrometry: mass calculated for C20H30CoO
345.16231, found 345.16234. Anal. Calcd for C20H30CoOPF6: C,
48.99; H, 6.17. Found: C, 50.15; H, 6.24.
1
(m). H NMR (400 MHz, chloroform-d3): δ 6.46 (d, 1H, J3−4 = 7.4
Hz, H3), 4.58 (ddd, 1H, J3−4 = 7.4 Hz, J4−5 = 9.0 Hz, J4−6eq = 1.2 Hz,
H4), 4.29 (ddd, 1H, J4−5 = 9.0 Hz, J5−6ax = 3.0 Hz, J5−6eq = 4.4 Hz, H5),
2.49 (ddd, 1H, J5−6ax = 3.0 Hz, J6ax−6eq = 16.8 Hz, J6ax−7 = 11.6 Hz,
H6ax), 2.20 (s, 3H, C2−CH3), 2.17 (ddt, 1H, J4−6eq = 1.2 Hz, J5−6eq
4.4 Hz, J6ax−6eq = 16.8 Hz, J6eq−7 = 4.4 Hz, H6eq), 1.74 (s, 15H,
=
CpMe5), 1.28 (s, 3H, C1−CH3), 0.86 (d, 3H, J7−CH = 6.8 Hz,
3
C7−CH3), 0.27 (m, 1H, J7−CH = 6.8 Hz, H7). H−1H GCOSY (400
1
3
MHz, chloroform-d3): δ 6.46 ↔ δ 4.58, δ 2.20; δ 4.58 ↔ δ 4.29, δ
2.17; δ 4.29 ↔ δ 2.49, δ 2.17; δ 2.49 ↔ δ 2.17, δ 0.27; δ 2.17 ↔ δ
0.27; δ 0.86 ↔ δ 0.27. 13C NMR (100 MHz, chloroform-d3): δ 108.4
(C2), 102.2 (C1), 98.8(C3), 97.5 (C5Me5), 96.4 (C4), 87.1 (C5), 50.3
(C6), 36.6 (C7), 19.5 (C1−CH3), 17.3 (C2−CH3), 16.0 (C7−CH3),
9.0 (C5Me5). HMQC (400 MHz, chloroform-d3): δ 98.8 ↔ δ 6.46; δ
96.4 ↔ δ 4.58; δ 87.1 ↔ δ 4.29; δ 50.3 ↔ δ 2.49, δ 2.17; δ 19.4 ↔ δ
1.28; δ 17.3 ↔ δ 2.20; δ 16.0 ↔ δ 0.86; δ 9.0 ↔ δ 1.74. HMBC
(400 MHz, chloroform-d3): δ 108.4 ↔ δ 6.46, δ 4.58, δ 2.20, δ 1.28; δ
102.2 ↔ δ 6.46, δ 2.20, δ 1.28, δ 0.86; δ 98.8 ↔ δ 4.29, δ 2.20; δ 97.5
↔ δ1.74; δ 96.4 ↔ δ 6.46, δ 2.49; δ 87.1 ↔ δ 6.46, δ 4.58, δ 2.49, δ
0.86; δ 50.3 ↔ δ 4.58, δ 0.86; δ 36.6 ↔ δ 4.29, δ 2.49, δ 1.28, δ 0.86;
δ 17.3 ↔ δ 6.46; δ 16.0 ↔ δ 1.28. Electrospray high-resolution mass
spectrometry: mass calculated for C20H30Co 329.16740, found
329.16741. Anal. Calcd for C20H30CoPF6: C, 50.64; H, 6.37. Found:
C, 50.53; H, 6.53.
−
Cp*Co(η5-7-methyl-2-propylcycloheptadienyl)+PF6− (3d)
and Cp*Co(η5-7-methyl-1-propylcycloheptadienyl)+PF6 (3d′).
A glass bomb was charged with a solution of 1a (17.8 mg, 0.0424 mmol)
in freshly distilled dichloromethane (∼1 mL). 1-Pentyne (25 μL,
∼0.25 mmol) was added via syringe, the bomb was sealed, and the
solution was maintained at 42 °C for 17 h. The solvent was removed
in vacuo, and the red residue was chromatographed on silica gel with a
3% methanol/dichloromethane eluent. The deep red fraction was
collected and, upon removal of solvent and subsequent drying under
high vacuum, a 69:31 mixture (as determined by 1H NMR integration)
of 3d and 3d′ (18.8 mg, 0.0385 mmol, 91%) was obtained. Although
pinhole diffusion of diethyl ether into dichloromethane afforded
analytically pure material, efforts to grow X-ray-quality crystals proved
fruitless. The product was characterized as a mixture, although the
NMR data for 3d and 3d′ are presented individually. IR (micro-
scope, cm−1): 2967 (s), 2934 (s), 2874 (s), 1578 (w), 1464 (s), 1384 (s),
1335 (w), 1316 (w), 1306 (w), 1241 (w), 1203 (w), 1156 (w), 1083
(m), 1026 (m), 968 (w), 936 (m), 906 (m), 857 (s), 775 (m), 741
(m), 724 (m). 1H NMR (600 MHz, chloroform-d3): major isomer 3d,
δ 6.38 (dd, 1H, J3−4 = 7.0 Hz, J1−3 = 1.6 Hz, H3), 4.96 (ddm, 1H,
Cp*CoIII 7-Methyl-2-ethoxycycloheptadienyl Hexafluorophos-
phate (3c) and Cp*CoIII 7-Methyl-1-ethoxy-cycloheptadienyl
Hexafluorophosphate (3c′). A glass bomb was charged with a
solution of 1a (29.2 mg, 0.0695 mmol) in freshly distilled
dichloromethane (∼1 mL). Ethoxyacetylene (50 μL, 40% solution in
hexanes, ∼0.29 mmol) was added via syringe, the bomb was sealed,
and the solution was maintained at 42 °C for 18 h. The solvent was
removed in vacuo, and the red residue was chromatographed on silica
gel with a 3% methanol/dichloromethane eluent. The deep red frac-
tion was collected and, upon removal of solvent and subsequent drying
under high vacuum, a 64:36 mixture (as determined by 1H NMR
integration) of 3c and 3c′ (27.9 mg, 0.0569 mmol, 82%) was obtained.
The product was characterized as a mixture, although the NMR data
for 3c and 3c′ are presented individually. IR (microscope, cm−1): 2979
(m), 2927 (m), 1471 (m), 1381 (m), 1326 (w), 1296 (w), 1234 (w),
1199 (m), 1176 (m), 1152 (w), 1103 (w), 1077 (w), 1026 (m), 875
J3−4 = 7.0 Hz, J4−5 = 9.1 Hz, H4), 4.40 (ddd, 1H, J4−5 = 9.1 Hz, J5−6ax
=
4.8 Hz, J5−6eq = 3.3 Hz, H5), 3.61 (dd, 1H, J1−7 = 3.5 Hz, J1−3 = 1.6 Hz,
H1), 2.51 (m, 1H, −CH2CH2CH3), 2.27 (ddd, 1H, J5−6ax = 4.8 Hz,
J6ax−6eq = 16.7 Hz, J6ax−7 = 8.8 Hz, H6ax), 1.95 (m, 1H, J5−6eq = 3.3 Hz,
J6ax−6eq = 16.7 Hz, H6eq), 1.84 (s, 15H, CpMe5), 1.8−1.7 (m, 3H,
−CH2CH2CH3 (1H) and −CH2CH2CH3 (2H)), 1.08 (d, 3H, J7−CH
=
6.8 Hz, C7−CH3), 1.00 (t, 3H, J = 7.1 Hz, −CH2CH2CH3), 0.85 (3m,
1H, J7−CH = 6.8 Hz, H7). 1H NMR (600 MHz, chloroform-d3): minor
3
1
(m), 838 (s), 739 (w). H NMR (400 MHz, chloroform-d): major
isomer 3c, δ 6.24 (dd, 1H, J3−4 = 7.2 Hz, J1−3 = 3.2 Hz, H3), 5.07 (ddd,
1H, J3−4 = 7.2 Hz, J4−5 = 9.0 Hz, J4−6eq = 1.4 Hz, H4), 4.31 (ddd, 1H,
isomer 3d′, δ 6.52 (app td, 1H, J2−3 = 7.0 Hz, J3−4 = 7.2 Hz, J3−5 = 1.2
Hz, H3), 5.19 (app t, 1H, J3−4 = 7.2 Hz, J4−5 = 6.5 Hz, H4), 4.93 (d,
1H, J2−3 = 7.0 Hz, H2), 4.28 (dddd, 1H, J4−5 = 6.5 Hz, J5−6ax = 7.5 Hz,
J4−5 = 9.0 Hz, J5−6ax = 5.5 Hz, J5−6eq = 3.3 Hz, H5), 4.12 (dq, 1H, Jgem
9.6 Hz, Jvic = 7.0 Hz, -OCH2CH3), 3.97 (dq, 1H, Jgem = 9.6 Hz, Jvic
7.0 Hz, −OCH2CH3), 3.75 (dd, 1H, J1−7 = 3.8 Hz, J1−3 = 3.2 Hz, H1),
2.03 (ddd, 1H, J5−6ax = 5.5 Hz, J6ax−6eq = 15.9 Hz, J6ax−7 = 6.8 Hz, H6ax),
1.82 (s, 15H, CpMe5), 1.64 (m, 1H, J5−6eq = 3.3 Hz, J6ax−6eq = 15.9 Hz,
=
=
J5−6eq = 5.0 Hz, J3−5 = 1.2 Hz, H5), 2.38 (ddd, 1H, Jgem = 12.7 Hz, Jvic =
10.0 Hz, Jvic = 4.6 Hz, −CH2CH2CH3), 1.94 (m, 1H, J7−CH = 6.8 Hz,
H7), 1.82 (s, 15H, CpMe5), 1.7 (m, 1H, −CH2CH2CH3), 31.51 (ddd,
1H, J5−6ax = 7.5 Hz, J6ax−6eq = 13.7 Hz, J6ax−7 = 2.8 Hz, H6ax), 1.45 (m,
1H, −CH2CH2CH3), 1.41 (d, 3H, J7−CH = 6.8 Hz, C7−CH3), 1.34
3
H6eq), 1.40 (t, 3H, J = 7.0 Hz, −OCH2CH3), 1.15 (d, 3H, J7−CH = 5.4
(ddd, 1H, Jgem = 12.7 Hz, Jvic = 10.6 Hz, Jvic = 6.2 Hz, −CH2CH2CH3),
0.98 (t, 3H, J = 7.3 Hz, −CH2CH2CH3), 0.49 (m, 1H, J5−6eq = 5.0 Hz,
J6ax−6eq = 13.7 Hz, H6eq). 1H−1H GCOSY (500 MHz, chloroform-d3): major
3
Hz, C7−CH3), 1.11 (m, 1H, J1−7 = 3.8 Hz, J7−CH = 5.4 Hz, J6ax−7 = 6.8
3
1
Hz, H7). H NMR (400 MHz, chloroform-d): minor isomer 3c′, δ
3346
DOI: 10.1021/acs.organomet.5b00346
Organometallics 2015, 34, 3335−3357

Organometallics
Article
isomer 3d, δ 6.38 ↔ δ 4.96, δ 4.40, δ 3.61; δ 4.96 ↔ δ 4.40, δ 1.95; δ
4.40 ↔ δ 2.27, δ 1.95; δ 3.61 ↔ δ 0.85; δ 2.51 ↔ δ 1.8, δ 1.7, δ 1.00; δ
2.27 ↔ δ 1.95, δ 0.85; δ 1.95 ↔ δ 0.85; δ 1.8 ↔ δ 1.7, δ 1.00; δ 1.7 ↔
δ 1.00; δ 1.08 ↔ δ 0.85. 1H−1H GCOSY (500 MHz, chloroform-d3):
minor isomer 3d′, δ 6.52 ↔ δ 5.19, δ 4.93, δ 4.28; δ 5.19 ↔ δ 4.93, δ
4.28, δ 0.49; δ 4.28 ↔ δ 1.51, δ 0.49; δ 2.38 ↔ δ 1.7, δ 1.45, δ 1.34; δ
1.94 ↔ δ 1.51, δ 1.41, δ 0.49; δ 1.7 ↔ δ 1.45, δ 1.34, δ 0.98; δ 1.51 ↔
δ 0.49; δ 1.45 ↔ δ 1.34, δ 0.98. 13C NMR (125 MHz, chloroform-d3):
major isomer 3d, δ 113.5 (C2), 99.0 (C3), 98.5 (C5Me5), 97.6 (C4),
91.1 (C5), 90.4 (C1), 46.3 (C6), 38.1 (−CH2CH2CH3), 36.0 (C7), 25.6
(−CH2CH2CH3), 22.4 (C7−CH3), 13.5 (−CH2CH2CH3), 9.7
(C5Me5). 13C NMR (125 MHz, chloroform-d3): minor isomer 3d′, δ
116.4 (C1), 99.8 (C4), 98.2 (C2), 97.9 (C5Me5), 97.2 (C3), 85.5 (C5),
46.2 (C7), 41.0 (−CH2CH2CH3), 36.2 (C6), 23.2 (−CH2CH2CH3),
22.0 (C7−CH3), 14.1 (−CH2CH2CH3), 9.6 (C5Me5). HMQC (500
MHz, chloroform-d3): major isomer 3d, δ 99.0 ↔ δ 6.38; δ 97.6 ↔ δ
4.96; δ 91.1 ↔ δ 4.40; δ 90.4 ↔ δ 3.61; δ 46.3 ↔ δ 2.27, δ 1.95; δ
38.1 ↔ δ 2.51, δ 1.7; δ 36.0 ↔ δ 0.85; δ 25.6 ↔ δ 1.8, δ 1.7; δ 22.4 ↔
δ 1.08; δ 13.5 ↔ δ 1.00; δ 9.7 ↔ δ 1.84. HMQC (500 MHz,
chloroform-d3): minor isomer 3d′, δ 99.8 ↔ δ 5.19; δ 98.2 ↔ δ 4.93; δ
97.2 ↔ δ 6.52; δ 85.5 ↔ δ 4.28; δ 46.2 ↔ δ 1.94; δ 41.0 ↔ δ 2.38, δ
1.34; δ 36.2 ↔ δ 1.51, δ 0.49; δ 23.2 ↔ δ 1.7, δ 1.45; δ 22.0 ↔ δ 1.41;
δ 14.1 ↔ δ 0.98; δ 9.6 ↔ δ 1.82. Electrospray high-resolution mass
spectrometry: mass calculated for C21H32Co 343.18305, found
343.18330. Anal. Calcd for C21H32CoPF6: C, 51.65; H, 6.60. Found:
C, 51.30; H, 6.35.
product as a thick, red oil. A sample suitable for combustion and X-ray
analysis was prepared by crystallization via two-chambered liquid
diffusion using CH2Cl2 and Et2O to yield red crystals. IR (CH2Cl2
cast, cm−1): 2920 (m), 1491 (w), 1456 (m), 1432 (w), 1384 (m),
1054 (s), 775 (m), 732 (m), 706 (m), 520 (w). 1H NMR (300 MHz,
CDCl3): δ 7.30−7.17 (m, 3H, Ph, overlaps solvent signal), 6.95 (m,
2H, Ph), 6.75 (d, J1−2 = 7.4 Hz, 1H, H1), 4.83 (t, J2−1 = J2−3 = 8.3 Hz,
1H, H2), 4.52 (dt, J3−2 = 9.2 Hz, J3−4endo = J3−4exo = 3.4 Hz, 1H, H3),
3.25 (ddd, J4endo−4exo = 16.5 Hz, J4endo−5 = 12.8 Hz, J4endo−3 = 3.1 Hz,
1H, H4endo), 2.39 (brapp dt, J4exo−4endo = 16.6 Hz, J4exo−5 = J4exo−3 = 4.8
Hz, 1H, H4exo, other couplings which do not resolve well are also
seen), 2.23 (s, 3H, Me), 1.80 (s, 15H, C5Me5), 1.30 (dd, J5−4endo = 12.8
Hz, J5−4exo = 4.0 Hz, 1H, H5), 0.84 (s, 3H, Me). 1H−1H GCOSY (300
MHz, CDCl3): δ 7.30−7.17 (Ph) ↔ δ 6.95 (Ph); δ 6.75 (H1) ↔ δ
4.83 (H2); δ 4.83 (H2) ↔ δ 4.52 (H3), 2.39 (H4endo); δ 4.52 (H3) ↔ δ
3.25 (H4endo), 2.39 (H4exo); δ 3.25 (H4endo) ↔ δ 2.39 (H4exo), 1.30
(H5); δ 2.39 (H4exo) ↔ δ 1.30 (H5). 13C{1H} NMR (100 MHz,
CDCl3): δ 137.7, 128.57, 128.55, 127.3, 108.5, 100.3, 99.7, 97.9, 96.5,
86.6, 47.1, 46.6, 21.7, 17.0, 9.1. Electrospray MS: m/z calculated for
C25H32Co (M+ − BF4) 391.18305, found 391.18328 (100%). Anal.
Calcd for C25H32CoBF4: C, 62.78; H, 6.74. Found: C, 62.95; H, 6.73.
−
[Cp*(η5-1-phenyl-3-trimethylsilylcyc−loheptadienyl)]+BF4
(3h). [Cp*Co(η5-1-phenylpentadienyl)]+BF4 (102 mg, 0.24 mmol)
was dissolved in CH2Cl2 (4 mL) in a reaction bomb and degassed with
argon for 5 min. To this was added TMS-acetylene (200 μL, 1.42 mmol).
The bomb was sealed and heated at 40 °C for 2 days. The solvent was
then removed in vacuo and the product purified by silica gel
chromatography using 3% MeOH/CH2Cl2. The red fraction was
collected and dried, providing 98 mg of product as a thick, red oil
which still contained significant impurities. The product yield (26%)
was determined by 1H NMR using 1,3,5-trimethoxybenzene as an
internal standard. Over several reactions, the yield was inexplicably
seen to range from as low as 26% to as high as 55%. A sample suitable
for combustion and X-ray analysis was prepared by crystallizing three
times via two-chambered liquid diffusion using CH2Cl2 and Et2O to
yield red crystals. IR (CH2Cl2 cast, cm−1): 3390 (w), 2957 (w), 2915
(w), 1601 (w), 1493 (m), 1454 (m), 1430 (m), 1383 (m), 1252 (m),
−
[Cp*Co(η5-1-phenylcycloheptadienyl)]+BF4 (3f). [Cp*Co(η5-
−
1-phenylpentadienyl)]+BF4 (105 mg, 0.25 mmol) was dissolved in
CH2Cl2 (3 mL) in a reaction bomb and degassed with argon for 5 min.
Simultaneously, acetylene was bubbled through CH2Cl2 in a test tube
for 25 min in order to ensure saturation. Then, 2 mL of this saturated
solution was transferred to the bomb via cannula. The bomb was
sealed and allowed to stand at room temperature for 3 days. During
this time, the color was seen to gradually change from dark red to
orange-red. The bomb was then heated at 60 °C in an oil bath for
1 day, and the color changed back to dark red. The solvent was re-
moved in vacuo and the product purified by silica gel chromatography
using 3% MeOH/CH2Cl2. The red fraction was collected and dried,
providing 111 mg (100%) of product as a thick, red oil. A sample
suitable for combustion analysis was obtained by crystallization via
two-chambered liquid diffusion using CH2Cl2 and Et2O to yield a light,
orange powder. IR (CH2Cl2 cast, cm−1): 3029 (w), 2917 (w), 1601
(w), 1493 (w), 1456 (w), 1384 (w), 1284 (w), 1056 (s), 878 (w), 762
(w), 732 (w), 704 (w). 1H NMR (400 MHz, CDCl3): δ 7.36 (m, 2H,
Ph), 7.27 (m, 1H, Ph, overlaps solvent signal), 7.12 (m, 2H, Ph), 6.90
(t, J3−2 = J3−4 = 6.3 Hz, 1H, H3), 5.42 (t, J2−1 = J2−3 = 7.1 Hz, 1H, H2),
1
1057 (s), 918 (w), 883 (w), 842 (s), 762 (m), 732 (w), 703 (m). H
NMR (400 MHz, CDCl3): δ 7.36 (t, J = 7.4 Hz, 2H, Ph), 7.26 (t, J =
7.3 Hz, 1H, Ph, overlaps solvent signal), 7.07 (d, J = 7.3 Hz, 2H, Ph),
6.73 (d, J3−4 = 6.9 Hz, 1H, H3), 5.25 (dd, J4−5 = 8.8 Hz, J4−3 = 7.5 Hz,
1H, H4), 4.79 (dt, J5−4 = 9.5 Hz, J5−6endo = J5−6exo = 3.6 Hz, 1H, H5),
3.93 (dd, J2−1 = 4.2 Hz, J2−3 = 0.7 Hz, 1H, H2), 3.06 (ddd, J6endo−6exo
=
17.1 Hz, J6endo−1 = 11.1 Hz, J6endo−5 = 4.2 Hz, 1H, H6endo), 2.36 (br app dt,
J6exo−6endo = 17.0 Hz, J6exo−1 = J6exo−5 = 3.6 Hz, 1H, H6exo), 1.90 (s,
15H, C5Me5), 1.48 (dt, J1−6endo = 10.8 Hz, J1−2 = J1−6exo = 4.8 Hz, 1H,
H1), 0.35 (s, 9H, SiMe3). 1H−1H GCOSY (400 MHz, CDCl3): δ 7.36
(Ph) ↔ δ 7.26 (Ph), 7.07 (Ph); δ 6.73 (H3) ↔ δ 5.25 (H4), 3.93 (H2);
δ 5.25 (H4) ↔ δ 4.79 (H5); δ 4.79 (H5) ↔ δ 3.06 (H6endo), 2.36
(H6exo); δ 3.93 (H2) ↔ δ 1.48 (H1); δ 3.06 (H6endo) ↔ δ 2.36 (H6exo),
1.48 (H1); δ 2.36 (H6exo) ↔ δ 1.48 (H1); 13C{1H} NMR (100 MHz,
CDCl3): δ 142.1, 129.1, 127.2, 126.6, 107.1, 102.3, 99.1, 98.0, 92.7,
91.6, 47.5, 47.2, 10.2, −0.7. Electrospray MS: m/z calculated for
C26H36SiCo (M+ − BF4) 435.19128, found 435.19152 (100%). Anal.
Calcd for C26H36SiCoBF4: C, 59.78; H, 6.95. Found: C, 59.98; H, 7.07.
5.16 (t, J4−3 = J4−5 = 8.6 Hz, 1H, H4), 4.52 (dt, J5−4 = 9.3 Hz, J5−6endo
=
J5−6exo = 3.7 Hz, 1H, H5), 4.32 (ddd, J1−2 = 8.1 Hz, J1−7 = 4.5 Hz, J1−3
=
1.1 Hz, 1H, H1), 2.99 (ddd, J6endo−6exo = 16.7 Hz, J6endo−7 = 10.4 Hz,
J6endo−5 = 4.2 Hz, 1H, H6endo), 2.30 (br app dt, J6exo−6endo = 16.7 Hz,
J6exo−5 = J6exo−7 = 3.7 Hz, 1H, H6exo), 1.91 (s, 15H, C5Me5), 1.78 (dt,
J7−6endo = 11.6, J7−1 = J7−6exo = 5.2 Hz, 1H, H7). 1H−1H GCOSY (400
MHz, CDCl3): δ 7.36 (Ph) ↔ δ 7.27 (Ph), 7.12 (Ph); δ 7.27 (Ph) ↔
δ 7.12 (Ph); δ 6.90 (H3) ↔ δ 5.42 (H2), 5.16 (H4), 4.32 (H1); δ 5.42
(H2) ↔ δ 4.32 (H1); δ 5.16 (H4) ↔ δ 4.52 (H5); δ 4.52 (H5) ↔ δ
2.99 (H6endo), 2.30 (H6exo); δ 4.32 (H1) ↔ δ 1.78 (H7); δ 2.99
(H6endo) ↔ δ 2.30 (H6exo), 1.78 (H7); δ 2.30 (H6exo) ↔ δ 1.78 (H7).
13C{1H} NMR (100 MHz, CDCl3): δ 141.8, 129.1, 127.3, 126.9,
101.1, 99.0, 98.1, 97.7, 95.1, 88.8, 49.0, 45.6, 9.8. Electrospray MS: m/z
calculated for C23H28Co (M+ − BF4), 363.15175, found 363.15171
(100%). Anal. Calcd for C23H28CoBF4: C, 61.36; H, 6.27. Found: C,
61.05; H, 6.03.
−
Cp*Co(η5-7-ethylcycloheptadienyl)+BF4 (3i). An NMR tube
was charged with a solution of 2d (11.1 mg, 0.161 mmol) in
dichloromethane-d2 (∼750 μL). The tube was tightly sealed, and the
reaction mixture was heated at 60 °C for 1 h, at which point 1H NMR
interrogation revealed an approximately 8% conversion to η5-
cycloheptadienyl product 3i. Heating at 60 °C was resumed; NMR
analysis revealed an approximately 75% conversion after 19 h and
complete conversion after 66 h. The deuterated solvent was removed
in vacuo, and the red-orange residue was chromatographed on silica
gel with 3% methanol/dichloromethane, furnishing 3i as an analyti-
cally pure powder (11.0 mg, 0.160 mol, 99%) after drying under high
vacuum. IR (microscope, cm−1): 2968 (m), 2918 (m), 2877 (m), 1496
(m), 1463 (m), 1434 (m), 1406 (s), 1380 (m), 1345 (w), 1313 (w),
1138 (w), 1076 (w), 1027 (m), 980 (w), 911 (w), 882 (s), 843 (s),
779 (w), 740 (w). 1H NMR (400 MHz, chloroform-d): δ 6.61 (app td,
−
[Cp*Co(η5-1-phenyl-2,3-dimethylcyc−loheptadienyl)]+BF4
(3g). [Cp*Co(η5-1-phenylpentadienyl)]+BF4 (101 mg, 0.24 mmol)
was dissolved in CH2Cl2 (4 mL) in a reaction bomb and degassed with
argon for 5 min. To this was added 2-butyne (100 μL, 1.28 mmol).
The bomb was sealed and allowed to stand at room temperature for
3 days. The solvent was then removed in vacuo and the product
purified by silica gel chromatography using 3% MeOH/CH2Cl2. The
red fraction was collected and dried, providing 110 mg (96%) of
3347
DOI: 10.1021/acs.organomet.5b00346
Organometallics 2015, 34, 3335−3357

Organometallics
Article
1H, J2−3 = 6.7 Hz, J3−4 = 6.9 Hz, J1−3 = 1.3 Hz, H3), 5.26 (ddm, 1H,
(dichloromethane/diethyl ether). IR (microscope, cm−1): 3388 (br,
3113 (w), 2972 (w), 1709 (w), 1522 (w), 1468 (m), 1435 (m), 1412
(m), 1382 (m), 1300 (w), 1053 (brs), 858 (s). H NMR (400 MHz,
J1−2 = 8.1 Hz, J2−3 = 6.7 Hz, H2), 4.90 (ddm, 1H, J3−4 = 6.9 Hz, J4−5
=
1
9.3 Hz, H4), 4.33 (ddd, 1H, J4−5 = 9.3 Hz, J5−6ax = 4.3 Hz, J5−6eq = 3.3
Hz, H5), 4.04 (ddd, 1H, J1−2 = 8.1 Hz, J1−7 = 4.0 Hz, J1−3 = 1.3 Hz,
H1), 2.37 (ddd, 1H, J5−6ax = 4.3 Hz, J6ax−6eq = 16.7 Hz, J6ax−7 = 9.4 Hz,
H6ax), 2.10 (dddd, 1H, J4−6eq = 1.4 Hz, J5−6eq = 3.3 Hz, J6ax−6eq = 16.7
CDCl3): δ 5.36 (m [overlapping with Cp], 1H, H3); 5.32 (s, 5H, Cp);
4.79 (dd, J = 4.5 Hz, J = 6.7 Hz, 1H, H1); 4.15 (t, J = 7.3 Hz, 1H, H2);
3.14 (dd, J = 9.3 Hz, J = 14.1 Hz, 1H, H4endo); 2.58 (t, J = 5.8 Hz, 1H,
H7exo); 2.53 (dd, J = 4.4 Hz, J = 14.1 Hz, 1H, H4exo); 2.04 (s, 3H,
Hz, J6eq−7 = 5.3 Hz, H6eq), 1.88 (s, 15H, CpMe5), 1.46 (dp, 1H, Jgem
=
1
14.6 Hz, JCH −CH = 7.3 Hz, J7−CH = 7.3 Hz, −CH2CH3), 1.36 (dp, 1H,
H8Me); 1.84 (s, 3H, H9Me); 1.54 (d, J = 7.0 Hz, 3H, H10endoMe). H
2
2
Jgem = 14.6 Hz, JC3 H −CH = 7.3 Hz, J7−CH = 7.3 Hz, −CH2CH3), 0.82 (t,
NMR (400 MHz, acetone-d6): δ 5.48 (s, 5H, Cp); 5.32 (ddd, 1H, H3);
4.86 (ddd, 1H, H1); 4.14 (t, J = 7.3 Hz, 1H, H2); 3.12 (dd, J = 9.3 Hz,
J = 14.2 Hz, 1H, H4endo); 2.70 (t, J = 6.2 Hz, 1H, H7exo); 2.63 (dd, J =
4.6 Hz, J = 14.0 Hz, 1H, H4exo); 2.09 (s, 3H, H8Me); 1.92 (s, 3H,
H9Me); 1.52 (d, J = 7.0 Hz, 3H, H10endoMe). GCOSY (300 MHz,
acetone-d6): δ 5.32 (H3) ↔ 4.14 (H2), 3.12 (H4endo); 4.86 (H1) ↔
4.14 (H2); 3.12 (H4endo) ↔ 2.63 (H4exo); 2.70 (H7exo) ↔ 1.52
(H10endoMe). 13C NMR (100 MHz, acetone-d6): δ 88.96 (Cp); 88.93
(C3); 88.85 (C2); 48.96 (C1); 32.05 (C7); 31.39 (C4); 23.70 (C8);
17.98 (C10); 16.00 (C9). gHSQC (400 MHz, acetone-d6): δ 88.96
(Cp) ↔ 5.48 (Cp); 88.85 (C2) ↔ 4.14 (H2); 48.96 (C1) ↔ 4.86 (H1);
32.05 (C7) ↔ 2.70 (H7exo); 31.39 (C4) ↔ 3.12 (H4endo), 2.63 (H4exo);
23.70 (C8) ↔ 2.09 (H8); 17.98 (C10) ↔ 1.52 (H10); 16.00 (C9) ↔
1.92 (H9) [missing correlation: 88.93 (C3) ↔ 5.32 (H3)]. Electrospray
MS: m/z calculated for C15H20Co (M+), 259.08915, found 259.08941.
Anal. Calcd for C15H20CoBF4: C, 52.06, H, 5.83; Found: C, 51.7911;
H, 5.7621.
3H, JCH −CH = 7.3 2Hz, −CH2CH3), 0.55 (m, 1H, J1−7 = 4.0 Hz, J6ax−7
=
3
2
2
3
9.4 Hz, J6eq−7 = 5.3 Hz, J7−CH = 7.3 Hz, H7). H−1H GCOSY (400
1
2
MHz, chloroform-d): δ 6.61 ↔ δ 5.26, δ 4.90, δ 4.04; δ 5.26 ↔ δ 4.04;
δ 4.90 ↔ δ 4.33, δ 2.10; δ 4.33 ↔ δ 2.37, δ 2.10; δ 4.04 ↔ δ 0.55; δ
2.37 ↔ δ 2.10, δ 0.55; δ 2.10 ↔ δ 0.55; δ 1.46 ↔ δ 1.36, δ 0.82, δ 0.55;
δ 1.36 ↔ δ 0.82, δ 0.55. 13C NMR (100 MHz, chloroform-d): δ 100.3
(C3), 98.3 (C5Me5), 97.7 (C2), 97.6 (C4), 94.9 (C1), 88.8 (C5), 46.4
(C6), 41.4 (C7), 29.3 (C7−CH2CH3), 12.0 (C7−CH2CH3), 9.7
(C5Me5). HMQC (400 MHz, chloroform-d): δ 100.3 ↔ δ 6.61; δ
97.7 ↔ δ 5.26; δ 97.6 ↔ δ 4.90; δ 94.9 ↔ δ 4.04; δ 88.8 ↔ δ 4.33; δ
46.4 ↔ δ 2.37, δ 2.10; δ 41.4 ↔ δ 0.55; δ 29.3 ↔ δ 1.46, δ 1.36; δ
12.0 ↔ δ 0.82; δ 9.7 ↔ δ 1.88. HMBC (400 MHz, chloroform-d):
δ 100.3 ↔ δ 4.33, δ 4.04; δ 98.3 ↔ δ 1.88; δ 97.7 ↔ δ 6.61, δ 4.90; δ
97.6 ↔ δ 6.61, δ 5.26, 2.37; δ 94.9 ↔ δ 6.46, δ 1.46, δ 1.36; δ 88.8 ↔ δ
6.46, δ 2.37; δ 46.4 ↔ δ 4.90, δ 4.04, δ 1.46, δ 1.36; δ 41.4 ↔ δ 5.26,
δ 2.37, δ 1.46, δ 1.36, δ 0.82; δ 29.3 ↔ δ 4.04, δ 2.37, δ 0.82; δ 12.0 ↔
δ 1.46, δ 1.36. Electrospray high-resolution mass spectrometry; mass
calculated for C19H28Co 315.15188, found 315.15175. Anal. Calcd for
C19H28CoPF6: C, 49.58; H, 6.13. Found: C, 49.52; H, 6.02.
[CpCo(η2,η3-1-trimethylsilylcyclohepta-2,5-dien-1-yl)][BF4]
(8c). Pentadienyl complex 7b (100 mg, 0.2856 mmol) was dissolved in
CH2Cl2 (3 mL) and placed in a reaction bomb. Simultaneously,
acetylene was bubbled through CH2Cl2 in a test tube for 20 min in
order to ensure saturation. Then, ∼2 mL of this saturated solution was
transferred to the bomb via cannula. The bomb was sealed and allowed
to stand at 40 °C over 3 days. The solvent was then removed in vacuo
and the product purified by silica gel chromatography using 3%
MeOH/CH2Cl2. The red fraction was collected and dried, providing
−
[CpCo(η2,η3-1-methylcycloheptadienyl)]+BF4 (8a). Complex
7a (100 mg, 0.3425 mmol) was dissolved in CH2Cl2 (3 mL) and
placed in a reaction bomb. Simultaneously, acetylene was bubbled
through CH2Cl2 in a test tube for 20 min in order to ensure saturation.
Then, ∼2 mL of this saturated solution was transferred to the bomb
via cannula. The bomb was sealed and allowed to stand at 40 °C over
3 days. The solvent was then removed in vacuo and the product
purified by silica gel chromatography using 3% MeOH/CH2Cl2. The
dark red fraction was collected and dried, providing 59.7 mg (55%) of
1
115.3 mg (94%) of 8c as a dark red powder. H NMR (400 MHz,
acetone-d6): δ 5.05 (m, 1H, H3), 4.95 (m, 1H, H1), 4.10 (m, 1H, H2),
3.90 (m, 1H, H5), 3.62 (m, 1H, H6), 3.10 (m, 1H, H4endo), 2.40 (m,
1H, H4exo), 1.88 (m, 1H, H7exo). GCOSY (400 MHz, acetone-d6): δ
5.05 (H3) ↔ 4.10 (H2), 3.10 (H4endo), 2.40 (H4exo); 4.95 (H1) ↔ 4.10
(H2), 1.88 (H7exo); 3.90 (H5) ↔ 3.62 (H6), 3.10 (H4endo); 3.62 (H6)
↔ 1.88 (H7exo); 3.10 (H4endo) ↔ 2.40 (H4exo). Electrospray MS: m/z
calculated for C15H22CoSi (M+) 289.08173, found 289.08147.
1
total product as a dark, red powder. By H NMR spectroscopy, this
fraction contained 8a with a small quantity of cobaltocenium by-
product. Crystals suitable for an X-ray diffraction analysis were grown
from pinhole diffusion (dichloromethane/diethyl ether) at room
temperature. IR (microscope, cm−1): 3401 (w), 3116 (w), 2936 (w),
2860 (w), 1636 (w), 1416 (s), 1299 (w), 1284 (w), 1054 (brs), 867
[CpCo(η2,η3-2,3-dimethyl-1-trimethylsilylcyclohepta-2,5-
dien-1-yl)][BF4] (8d). A glass reaction bomb was charged with a
solution of 7b (100 mg, 0.2856 mmol) in dichloromethane (∼3 mL).
An aliquot of 2-butyne (224 μL, ∼2.856 mmol) was injected via
syringe. The bomb was sealed, and the solution was maintained at
42 °C for 72 h. The solvent was removed in vacuo, and the red residue
was chromatographed on silica gel with a 3% methanol/dichloro-
methane eluent. The deep red fraction was collected and, upon
removal of solvent, was a powder that was identified as complex 8d
with a trace (∼5% by NMR spectroscopy) of the desilylated fully
1
(s). H NMR (400 MHz, acetone-d6): δ 5.75 (s, 5H, Cp); 5.10 (m,
1H, H3); 4.70 (m, 1H, H1); 4.10 (t, 1H, H2); 3.85 (dd, 1H, H5); 3.39
(m, 1H, H6); 3.12 (m, 1H, H4endo); 2.55 (m, 1H, H7exo); 2.28 (m, 1H,
H4exo); 1.53 (d, 3H, H8endoMe). GCOSY (400 MHz, acetone-d6): δ
5.10 (H3) ↔ 4.10 (H2), 3.12 (H4endo), 2.28 (H4exo); 4.70 (H1) ↔ 4.10
(H2), 2.55 (H7exo); 3.85 (H5) ↔ 3.39 (H6), 3.12 (H4endo), 2.28
(H4exo); 3.39 (H6) ↔ 2.55 (H7exo); 3.12 (H4endo) ↔ 2.28 (H4exo); 2.55
1
(H7exo) ↔ 1.53 (H8endoMe). H NMR (400 MHz, CDCl3): δ 5.61 (s,
5H, Cp); 5.04 (ddd, 1H, H3); 4.58 (dd, J = 3.7 Hz, J = 7.3 Hz, 1H,
H1); 4.01 (t, J = 7.5 Hz, 1H, H2), 3.73 (dd, J = 7.0 Hz, 1H, H5); 3.14−
3.24 (m, 2H, H6 + H4endo); 2.39 (dd, 1H, H7exo); 2.14 (dd, 1H, H4exo);
1.52 (d, 3H, H8endoMe). GCOSY (400 MHz, CDCl3): δ 5.04 (H3) ↔
4.01 (H2), 3.14 (H4endo), 2.14 (H4exo); 4.58 (H1) ↔ 4.01 (H2), 2.39
(H7exo); 3.73 (H5) ↔ 3.24 (H6); 3.24 (H6) ↔ 2.39 (H7exo); 3.14
(H4endo) ↔ 2.14 (H4exo); 2.39 (H7exo) ↔ 1.52 (H8endoMe). Electrospray
MS: m/z calculated for C13H16Co (M+) 231.05785, found 231.05809.
1
conjugated product 9b. H NMR (500 MHz, CDCl3): δ 5.43 (ddd,
1H, H3), 5.37 (s, 5H, Cp), 5.05 (dd, J = 5.9, J = 6.8 Hz, 1H, H1), 4.29
(dd, J = 6.1, J = 7.1 Hz, 1H, H2), 3.18 (dd, J = 9.5 Hz, J = 14.2 Hz, 1H,
H4exo), 2.68 (dd, J = 3.4 Hz, J = 14.4 Hz, 1H, H4endo), 2.10 (s, 3H,
H10Me), 2.02 (s, 3H, H9Me), 1.90 (d, J = 5.9 Hz, 1H, H7exo), 0.40 (s, 9H,
C8TMSMe). GCOSY (300 MHz, CDCl3): 5.43 (H3) ↔ 4.29 (H2), 3.18
(H4exo), 2.68 (H4endo); 5.05 (H1) ↔ 4.29 (H2), 1.90 (H7exo); 3.18
(H4exo) ↔ 2.68 (H4endo). 13C NMR (125 MHz, CDCl3): δ 88.88 (C2),
88.09 (Cp), 62.22 (C5), 61.29 (C6), 44.43 (C3), 40.84 (C1), 31.50
(C4), 28.12 (C7), 22.85 (C9), 21.22 (C10), −1.76 (C8). Electrospray
MS: m/z calculated for C17H26CoSi (M+) 317.11298, found 317.11303.
−
[CpCo(η2,η3-1,2,3-trimethylcycloheptadienyl)]+BF4 (8b). A
glass reaction bomb was charged with a solution of 7a (100 mg,
0.3425 mmol) in dichloromethane (∼3 mL). An aliquot of 2-butyne
(∼268 μL, 3.425 mmol) was injected via syringe. The bomb was
sealed, and the solution was maintained at 42 °C for 72 h. The solvent
was removed in vacuo, and the red residue was chromatographed on
silica gel with a 3% methanol/dichloromethane eluent. The deep red
fraction was collected and, upon removal of solvent, was comprised
primarily of the desired product but contained traces (less than 5%
−
[CpCo(η2,η3-1-phenylcycloheptadienyl)]+BF4 (8e). Complex
7c (100 mg, 0.2825 mmol) was dissolved in CH2Cl2 (3 mL) and
placed in a reaction bomb. Simultaneously, acetylene was bubbled
through CH2Cl2 in a test tube for 20 min in order to ensure saturation.
Then, ∼2 mL of this saturated solution was transferred to the bomb
via cannula. The bomb was sealed and allowed to stand at room tem-
perature over 3.5 days. The solvent was then removed in vacuo and the
1
each by H NMR integration) of minor impurities. Analytically pure
8b (51 mg, 43%) was obtained using pinhole diffusion crystallization
3348
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Organometallics
Article
product purified by silica gel chromatography using 3% MeOH/
CH2Cl2. The red fraction was collected and dried, providing 74.4 mg
(69%) of total product as a dark red powder. The 1H NMR spectrum
showed that there was a majority (ca. 83%) of starting complex 7c and
ca. 17% of 8e. IR (microscope, cm−1): 3520 (br, 3119 (m), 3026 (w),
2928 (m), 1668 (m), 1643 (m), 1619 (m), 1494 (w), 1450 (w), 1417
(H1/H3) ↔ 4.08 (H2), 3.15 (H4exo/H7exo), 2.30 (H4endo/H7endo); 4.08
(H2) ↔ 3.15 (H4exo/H7exo), 2.30 (H4endo/H7endo); 3.80 (H5/H6) ↔
3.15 (H4exo/H7exo), 2.30 (H4endo/H7endo); 3.15 (H4exo/H7exo) ↔ 2.30
(H4endo/H7endo). Electrospray MS: m/z calculated for C12H14Co (M+)
217.04220, found 217.04219.
−
[CpCo(η2,η3-1,2-dimethylcycloheptadienyl)]−+BF4 (8h) and
[CpCo(η5-1,2- dimethylcycloheptadienyl)]+BF4 (9e). A glass re-
action bomb was charged with a solution of 7d (100 mg, 0.3601 mmol) in
dichloromethane (∼3 mL). An aliquot of 2- butyne (282 μL, ∼3.601 mmol)
was injected via syringe. The bomb was sealed, and the solution was
maintained at 42 °C for 72 h. The solvent was removed in vacuo, and
the red residue was chromatographed on silica gel with a 3%
methanol/dichloromethane eluent. Two deep red fractions were
collected, and upon removal of solvent, the first fraction proved to be a
mixture of the allyl-olefin product and an unknown byproduct (1:2)
and the second fraction was the starting material.
1
(w), 1286 (w), 1054 (brs), 866 (m), 753 (m), 700 (m). H NMR
(500 MHz, CDCl3): δ 7.58 (m, 2H, Ph), 7.45 (m, 3H, Ph), 5.70 (s,
5H, Cp), 5.18 (ddd, 1H, H1), 4.95 (dd, 1H, H3), 4.15 (t, J = 7 Hz, 1H,
H2), 3.89 (ddd, 1H, H6), 3.57 (dd, 1H, H5), 3.44 (dd, 1H, H4endo),
2.34 (dd, 1H, H7exo or H4exo), 1.60 (m, 1H, H4exo or H7exo). GCOSY
(500 MHz, CDCl3): δ 7.55 (Ph) ↔ 7.45 (Ph); 4.95 (H3) ↔ 3.44
(H4endo); 3.89 (H6) ↔ 2.34 (H7exo). Electrospray MS: m/z calculated
for C18H18Co (M+) 293.07350, found 293.07370.
−
[CpCo(η2,η3-2,3-dimethyl-1-phenylcycloheptadienyl)]+BF4
(8f) and [CpCo(η5-2,3-dimethyl-1-phenylcycloheptadie-
nyl)]+BF4 (9c). A glass reaction bomb was charged with a solution
−
The above procedure was repeated with heating to 65 °C for 72 h,
isolating a single red fraction from column chromatography to
provide 66.8 mg (56%) of total product as a red powder. By NMR
spectroscopy, this fraction contained a mixture of the fully conjugated
product 9e and an unknown byproduct (1:3). Neither silica gel
column chromatography nor pinhole diffusion crystallization (ether
into dichloromethane) achieved further separation of the two com-
of complex 7c (100 mg, 0.2825 mmol) in dichloromethane (∼4 mL).
The bomb was sealed, and the solution was maintained at 42 °C for
72 h. The solvent was removed in vacuo, and the red residue was
chromatographed on silica gel with a 3% methanol/dichloromethane
eluent. The deep red fraction was collected and, upon removal of
solvent, provided 72.4 mg (63%) of total product as a red oily residue.
The 1H NMR spectrum showed that this product mixture was a
majority (ca. 87%) of 8f and only a minor amount (ca. 13%) of fully
conjugated 9c. The sample was purified by recrystallization using
pinhole diffusion to provide an analytically pure sample of the mixture
of isomers. Data for 9c are as follows. 1H NMR (500 MHz, CDCl3): δ
7.55 (d, 3H, Ph), 7.37 (t, 2H, Ph), 7.28 (m, 1H, H3), 5.76 (m, 1H,
H4), 5.64 (s, 5H, Cp), 5.34 (m, 1H, H5), 3.88 (m, 1H, H6exo), 2.38 (m,
1H, H6endo), 2.08 (s, 3H, H8), 1.52 (m, 1H, H7exo) 1.40 (s, 3H, H9).
GCOSY (500 MHz, CDCl3): δ 7. 55 (d, 3H, Ph) ↔ 7.37 (t, 2H, Ph);
7.28 (m, 1H, H3) ↔ 5.76 (m, 1H, H4); 5.34 (m, 1H, H5) ↔ 2.38 (m,
1H, H6endo); 3.88 (m, 1H, H6exo) ↔ 2.38 (m, 1H, H6endo), 1.52 (m, 1H,
H7exo); 2.38 (m, 1H, H6endo) ↔ 1.52 (m, 1H, H7exo). Data for 8f are as
1
pounds. Data for 8h are as follows. H NMR (400 MHz, acetone-d6):
δ 5.45 (s, 5H, Cp); 5.40 (ddd, 2H, H1/H3); 4.20 (t, 1H, H2); 3.11 (dd,
2H, H4endo/H7endo); 2.67 (dd, 2H, H4exo/H7exo); 2.20 (s, 3H, H8/H9).
GCOSY (400 MHz, acetone-d6): δ 5.40 (H1/H3) ↔ 4.20 (H2), 3.11
(H4endo), 2.67 (H4exo); 3.11 (H4endo) ↔ 2.67 (H4exo). Data for 9e (A)
1
are as follows. H NMR (400 MHz, acetone-d6): δ 7.17 (d, J2−3 = 7.3
Hz, 1H, H3), 5.65 (m, 1H, H2), 5.57 (s, 5H, Cp), 5.23 (ddd, J1−2 = 9.1
Hz, J1−7endo = 7.5 Hz, J1‑3= 1.5 Hz, 1H, H1), 3.19 (dddd, J7endo−7exo
=
19.9 Hz, J7endo−6exo = 11.7 Hz, J7endo−1 = 7.7 Hz, J7endo−6endo = 3.5 Hz,
1H, H7endo), 2.45 (s, 3H, H8), 2.05 (m, 1H, H7exo), 1.84 (s, 3H, H9),
1.50 (ddt, J6endo−6exo = 12.3 Hz, J6endo−7endo = 7.7 Hz, J6endo−7exo/9 = 1.5
Hz, 1H, H6endo), 0.32 (dt, J6exo−6endo/7exo = 12.4 Hz, J6exo−7exo = 5.3 Hz,
1H, H6exo). GCOSY (400 MHz, acetone- d6): δ 7.17 (H3) ↔ 5.23
(H1), 2.45 (H8), 1.84 (H9); 5.65 (H2) ↔ 5.23 (H1), 3.19 (H7endo),
2.05 (H7exo), 1.50 (H6endo); 5.23 (H1) ↔ 2.05 (H7exo); 3.19 (H7endo) ↔
2.05 (H7exo), 1.50 (H6endo), 0.32 (H6exo); 2.05 (H7exo) ↔ 0.32 (H6exo);
1.50 (H6endo) ↔ 0.32 (H6exo). Data for the unknown byproduct (B)
are as follows. 1H NMR (400 MHz, acetone-d6): δ 7.37 (d, J = 5.4 Hz,
1H), 5.65 (s, 5H, Cp), 5.59 (m, 1H), 3.83 (d, 1H), 2.20 (s, 3H), 1.63
(d, J = 12.5 Hz, 8H). GCOSY (500 MHz, acetone-d6): δ 7.37 ↔ 5.59,
3.83, 2.20, 1.63; 5.59 ↔ 3.83, 2.20, 1.63; 3.83, ↔ 1.63. Data for a
mixture of compounds A and B are as follows. IR (microscope, cm−1):
3113 (w), 2976 (w), 2942 (w), 2883 (w), 2835 (w), 1699 (w), 1458
(w), 1432 (w), 1411 (w), 1388 (w), 1285 (w), 1250 (w), 1055 (brs),
856 (w). 13C NMR (125 MHz, acetone-d6): δ 111.0, 108.0, 107.9,
99.1, 91.9, 91.2, 90.4, 89.1, 87.8, 87.6, 87.2, 86.9, 70.0, 55.7, 41.1, 33.8,
27.6, 20.4, 18.9, 18.4, 17.3, 11.8, 10.4. gHMQC (500 MHz, acetone-
d6): δ 99.3 ↔ 7.18 (B, H2), 92.0 ↔ 7.36 (A, H2), 87.6 ↔ 5.65 (A),
89.2 ↔ 5.56 (B), 55.9 ↔ 3.84 (B), 33.90 ↔ 1.61 (B), 27.6 ↔ 1.84 (A,
Me), 19.0 ↔ 1.62, 18.3 ↔ 2.15 (A), 17.4 ↔ 1.67, 17.1 ↔ 1.60.
Electrospray MS: m/z calculated for C14H18Co (M+) 245.07350, found
245.07387.
follows. H NMR (500 MHz, CDCl3): δ 7.53 (m, 2H, Ph), 7.48 (m,
1
3H, Ph), 5.43 (ddd, 1H, H3), 5.38 (s, 5H, Cp), 4.25 (t, 1H, H2), 3.67
(dd, 1H, H1), 3.24 (dd, 1H, H4endo), 2.74 (dd, 1H, H4exo), 2.38 (m, 1H,
H7exo), 2.06 (s, 3H, H8), 1.39 (s, 3H, H9). GCOSY (400 MHz,
CDCl3): δ 7.53 (Ph) ↔ 7.48 (Ph); 5.43 (H3) ↔ 4.25 (H2), 3.67 (H1),
3.24 (H4endo), 2.74 (H4exo); 3.67 (H1) ↔ 2.38 (H7exo); 3.24 (H4endo) ↔
2.74 (H4exo). Electrospray MS: m/z calculated for C20H22Co (M+)
321.10507, found 321.10480. Anal. Calcd for C15H17CoBF4: C, 58.86;
H, 5.43; Found, C, 59.1655; H, 5.5673.
−
[CpCo(η2,η3-cycloh−eptadienyl)]+BF4 (8g) and [CpCo(η5-cy-
cloheptadienyl)]+BF4 (9d). η5-Pentadienyl complex 7d (100 mg,
0.3601 mmol) was dissolved in CH2Cl2 (3 mL) and placed in a glass
reaction bomb. Simultaneously, acetylene was bubbled through
CH2Cl2 in a test tube for 20 min in order to ensure saturation.
Then, ∼2 mL of this saturated solution was transferred to the bomb
via cannula. The bomb was sealed and heated to 60 °C over 24 h. The
solution turned from orange to red. The solvent was then removed in
vacuo and the product purified by silica gel chromatography using 3%
MeOH/CH2Cl2. The red fraction was collected and dried, providing
68.4 mg (63%) of product as a dark red powder. The 1H NMR
spectrum showed that this was a mixture of the η3:η2 isomer and fully
conjugated η5 isomer in a 24:76 ratio. Although the product was
characterized as a mixture, the NMR data are presented separately.
Data for the isomeric mixture are as follows. IR (microscope, cm−1):
3479 (br, 3119 (s), 2934 (w), 2856 (w), 1709 (w), 1418 (s), 1286
[CpCo(η5-1,2,3-trimethylcycloheptadienyl)]+BF4− (9a). A glass
reaction bomb was charged with a solution of 7a (100 mg,
0.2890 mmol) in dichloroethane (∼4 mL). The bomb was sealed,
and the solution was maintained at 85−90 °C for 24 h. The solvent
was removed in vacuo, and the red residue was chromatographed on
silica gel with a 3% methanol/dichloromethane eluent. The deep red
fraction was collected, and upon removal of solvent, the sample was
comprised primarily of the desired product but contained traces (less
than 5% each by 1H NMR integration) of minor impurities (99%). IR
(microscope, cm−1): 3115 (m), 2973 (m), 2880 (m), 1474 (s), 1431
1
(m), 1054 (brs), 867 (s). Data for 9d are as follows. H NMR (400
MHz, acetone-d6): δ 7.41 (t, 1H, H3), 5.80 (dt, 2H, H2/H4), 5.78
(overlap with H2/H4, s, 5H, Cp), 5.60 (m, 2H, H1/H3), 2.49 (dd, 2H,
H6endo/H7endo), 1.25 (d, 2H, H6exo/H7exo). 1H−1H GCOSY (400 MHz,
acetone-d6): δ 7.41 (H3) ↔ 5.80 (H2/H4); 5.80 (H2/H4) ↔ 5.60
(H1/H3); 5.60 (H1/H3) ↔ 2.49 (H6endo/H7endo), 1.25 (H6exo/H7exo);
2.49 (H6endo/H7endo) ↔ 1.25 (H6exo/H7exo). Data for 8g are as follows.
1H NMR (400 MHz, acetone-d6): δ 5.10 (m, 2H, H1/H3), 4.08 (t, 1H,
H2), 3.80 (m, 2H, H6/H7), 3.15 (m, 2H, H4exo/H7exo), 2.30 (dd,
1
(s), 1413 (s), 1012 (s), 857 (s). H NMR (500 MHz, acetone-d6): δ
7.21 (d, J3−2 = 7.2 Hz, 1H, H3); 5.59 (s, 5H, Cp); 5.52 (obscured by
Cp, m, 1H, H5); 5.21 (t, J4−3/5 = 8.1 Hz, 1H, H4); 2.95 (ddd, J6endo−6exo
=
17.3, J6endo−5 = 11.7 Hz, J6endo−7exo = 3.4 Hz, 1H, H6endo); 2.50 (s, 3H,
H8); 2.15 (dddd, J6exo−6endo = 17.4 Hz, J6exo−7exo = 4.2 Hz, J6exo−5 = 1.6 Hz,
1
2H, H4endo/H7endo). H−1H GCOSY (400 MHz, acetone-d6): δ 5.10
3349
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1H, H6exo); 1.75 (s, 3H, H9); 0.97 (d, J10−6exo = 6.8 Hz, 3H, H10); 0.42
(ddd, J7exo−6exo = 4.6 Hz, J7exo−10 = 6.9 Hz, 1H, H7exo). GCOSY (500
MHz, acetone-d6) δ 7.21 (H3) ↔ 5.21 (H4), 2.50 (H8), 1.75 (H9);
5.52 (H5) ↔ 5.21 (H4), 2.95 (H6endo), 2.15 (H6exo); 5.21 (H4) ↔ 2.15
(H6exo); 2.95 (H6endo) ↔ 2.15 (H6exo), 0.42 (H7exo); 2.15 (H6exo) ↔
0.42 (H7exo); 0.97 (H10) ↔ 0.42 (H7exo). 13C NMR (125 MHz,
acetone-d6): δ 111.51 (C2), 110.52 (C1), 99.30 (C3), 91.07 (C4), 89.39
(Cp), 84.20 (C5), 50.56 (C6), 37.00 (C7), 23.53 (C9), 20.53 (C8),
16.06 (C10). gHSQC (500 MHz, acetone-d6): δ 99.30 (C3) ↔ 7.21
(H3); 91.07 (C4) ↔ 5.21(H4); 89.39 (Cp) ↔ 5.59 (Cp); 84.20
(C5) ↔ 5.52 (H5); 50.56 (C6) ↔ 2.95 (H6endo), 2.15 (H6exo); 37.00
(C7) ↔ 0.42 (H7); 23.53 (C9) ↔ 1.75 (H9); 20.53 (C8) ↔ 2.50 (H8);
16.06 (C10) ↔ 0.97 (H10); gHMBC (500 MHz, acetone-d6): δ 111.51
(C2) ↔ 2.50 (H8), 2.15 (H6exo); 110.52 (C1) ↔ 1.75 (H9), 0.97 (H10);
δ 99.30 (C3) ↔ 2.50 (H8); 91.07 (C4) ↔ 2.95(H6endo); 84.20 (C5) ↔
2.95(H6endo); 50.56 (C6) ↔ 5.21 (H4), 1.75 (H9), 0.97 (H10), 0.42
(H6exo); 37.00 (C7) ↔ 5.52 (H5), 2.95 (H6endo), 1.75 (H9), 0.97 (H10);
20.53 (C8) ↔ 7.21 (H3). Electrospray MS: m/z calculated for
C15H20Co (M+) 259.08915, found 259.08897. Anal. Calcd for
C15H20CoBF4: C, 52.06, H, 5.83; Found: C, 51.8668; H, 5.8396.
(E)-Dimethyl 2-(Hepta-1,4-diene-3-ol)malonate (15). Alde-
hyde 13 (1.6 g, 7.5 mmol), was dissolved in THF (5 mL) in a dry
Schlenk flask under an argon atmosphere. The flask was cooled to
−78 °C in a dry ice/acetone bath, and vinyl Grignard (0.34 M in THF,
44 mL, 15 mmol) was added via cannula. The mixture was stirred at
−78 °C for 30 min and then warmed to room temperature. The flask
was cooled again and the reaction quenched with aqueous NH4Cl.
This mixture was extracted with diethyl ether, washed with water and
then brine, and dried over NaSO4. The solvent was removed in vacuo
and the product purified via triethylamine neutralized silica gel
chromatography with 4:1 hexanes/EtOAc on the bench. The solvent
was removed to yield 1.1 g (60%) of dienol 15 as a clear oil. IR
(neat, cm−1): 3447 (br m), 3008 (w), 2956 (m), 2850 (w), 1737 (s),
1438 (m), 1346 (w), 1245 (m), 1201 (m), 1158 (m), 1082 (w), 992
(m), 972 (m), 925 (w), 692 (w). 1H NMR (400 MHz, CDCl3): δ 5.80
(ddd, J2−1trans = 16.1 Hz, J2−1cis = 10.3 Hz, J2−3 = 5.7 Hz, 1H, H2), 5.57
(dtd, J5−4 = 15.5 Hz, J5−6 = 6.3 Hz, J5−3 = 0.8 Hz, 1H, H5), 5.45 (ddt,
obtain analytical purity. IR (neat, cm−1): 3455 (br s), 3082 (w), 2958
(s), 2850 (s), 1737 (s), 1641 (w), 1438 (s), 1346 (s), 1261 (s), 1156
(s), 1091 (s), 1016 (s), 924 (m), 873 (w), 800 (m), 699 (w). 1H NMR
(400 MHz, CDCl3): δ 5.87 (ddd, J2−1trans = 17.2 Hz, J2−1cis = 10.4 Hz,
J2−3 = 5.8 Hz, 1H, H2), 5.65 (dtd, J5−4 = 15.3 Hz, J5−6 = 6.5 Hz, J5−3
=
0.7 Hz, 1H, H5), 5.50 (ddt, J4−5 = 15.5 Hz, J4−3 = 6.5 Hz, J4−6 = 1.3 Hz,
1H, H4), 5.23 (dt, J1trans‑2 = 17.2 Hz, J1trans‑1cis = J1trans‑3 = 1.4 Hz, 1H,
H1trans), 5.10 (dt, J1cis‑2 = 10.4, J1cis‑1trans = J1cis‑3 = 1.4 Hz, 1H, H1cis),
4.56 (br m, 1H, H3), 3.72 (s, 6H, −OMe), 3.34 (t, J9−8 = 7.6 Hz, 1H,
H9), 2.06 (q, J6−5 = J6−7 = 7.1 Hz, 2H, H6), 1.89 (m, 2H, CH2), 1.57
(d, JHO‑3 = 3.8 Hz, 1H, −OH), 1.40 (m, 2H, CH2). 13C{1H} NMR
(100 MHz, CDCl3): δ 169.6, 139.6, 131.7, 131.4, 114.7, 73.6, 52.3,
51.4, 31.6, 28.2, 26.6. Electrospray MS: m/z calculated for
C13H20O5Na (M+ + Na) 279.12030, found 279.12020 (100%). Anal.
Calcd for C13H20O5: C, 60.92; H, 7.87. Found: C, 61.21; H, 7.92.
(E)-2-Heptenal 6-Acetal (19). Protected allyl acetone 18 (1.34 g,
9.43 mmol) and crotonaldehyde (3.9 mL, 47.15 mmol) were dissolved
in CH2Cl2 (15 mL) under an argon atmosphere. Second-generation
Grubbs catalyst (120 mg, 0.14 mmol) was added and the reaction
mixture heated under reflux for 90 min. The solvent was removed in
vacuo and the product purified by silica gel chromatography using 4:1
hexanes:EtOAc to provide 1.38 g (86%) of aldehyde 19 as a clear oily
liquid. IR (neat, cm−1): 2984 (s), 2956 (m), 2886 (s), 2736 (w), 1690
(s), 1637 (m), 1479 (w), 1449 (w), 1378 (m), 1302 (w), 1255 (s),
1
1222 (s), 1150 (s), 1053 (s), 979 (m), 949 (m), 867 (s). H NMR
(300 MHz, CDCl3): δ 9.49 (d, J1−2 = 7.9 Hz, 1H, H1), 6.87 (dt, J3−2
=
15.6 Hz, J3−4 = 6.7 Hz, 1H, H3), 6.10 (ddt, J2−3 = 15.6 Hz, J2−1 = 7.9
Hz, J2−4 = 1.6 Hz, 1H, H2), 3.90 (m, 4H, −OCH2CH2O−), 2.45 (m,
1
2H, H4), 1.86 (m, 2H, H5), 1.33 (s, 3H, Me). H−1H GCOSY (400
MHz, CDCl3): δ 9.49 (H1) ↔ δ 6.10 (H2); δ 6.87 (H3) ↔ δ 6.10
(H2), 2.45 (H4); δ 6.10 (H2) ↔ δ 2.45 (H4); δ 2.45 (H4) ↔ δ 1.86
(H5). Electron impact MS: m/z calculated for C9H14O3 (M+)
170.09430, found 170.09481 (0.28%). 13C NMR (100 MHz, CDCl3):
δ 193.8, 158.4, 132.5, 109.1, 64.6, 36.9, 27.1, 23.9. Anal. Calcd for
C9H14O3: C, 63.51; H, 8.29. Found: C, 63.28; H, 8.31.
(E)-Nona-1,4-dien-3-ol 8-Acetal (20). A solution of vinyl
Grignard (0.34 M in THF, 18.2 mL, 6.18 mmol) was added to a
flame-dried Schlenk flask under an argon atmosphere and cooled
to −78 °C in a dry ice/acetone bath. To the resulting slurry was added
slowly aldehyde 19 (1.01 g, 5.88 mmol) via syringe. The mixture was
stirred at −78 °C for 30 min and then warmed slowly to room
temperature and stirred for an additional 15 min. The solution was
cooled again and quenched slowly with aqueous NH4Cl. The resulting
mixture was extracted with ether, washed with water and then brine,
and dried over NaSO4. The solvent was removed in vacuo and the
product purified by silica gel chromatography with 4:1 hexane/EtOAc
to provide 0.88 g (75%) of dienol 20 as a thick, pale yellow oil. IR
(neat, cm−1): 3440 (br s), 3080 (w), 2982 (s), 2947 (s), 2882 (s),
2678 (w), 1845 (w), 1668 (m), 1641 (m), 1477 (m), 1450 (m), 1422
(m), 1377 (s), 1344 (w), 1252 (s), 1221 (s), 1119 (s), 1058 (s), 974
(s), 949 (s), 923 (s), 862 (s), 817 (w), 787 (w), 762 (w), 668 (m). 1H
J4−5 = 16.3 Hz, J4−3 = 5.1 Hz, J4−6 = 1.1 Hz, 1H, H4), 5.16 (dt, J1trans‑2
17.2 Hz, J1trans‑1cis = J1trans‑3 = 1.5 Hz, 1H, H1trans), 5.04 (dt, J1cis‑2 = 10.4
Hz, J1cis‑1trans = J1cis‑3 = 1.3 Hz, 1H, H1cis), 4.49 (br app t, J3−2 = J3−4
=
=
5.6 Hz, 1H, H3), 3.65 (s, 6H, −OMe), 3.31 (t, J8−7 = 7.4 Hz, 1H, H8),
2.18 (br s, 1H, −OH), 2.01 (m, 2H, CH2), 1.92 (m, 2H, CH2).
13C{1H} NMR (100 MHz, CDCl3): δ 169.6, 139.5, 132.7, 129.8,
114.6, 73.2, 52.3, 50.7, 29.6, 27.9. Electrospray MS: m/z calculated for
C12H18O5Na (M+ + Na) 265.10465, found 265.10463 (100%). Anal.
Calcd for C12H18O5: C, 59.49; H, 7.49. Found: C, 59.44; H, 7.60.
(E)-Dimethyl 2-(Octa-1,4-diene-3-ol)malonate (15). 2-(1-Penten)-
dimethyl malonate (3.7 g, 18 mmol) and crotonaldehyde (4.5 mL,
54 mmol) were dissolved in CH2Cl2 (25 mL) in a dry three-neck
round-bottom flask. Second-generation Grubbs metathesis catalyst
(230 mg, 0.27 mmol) was added and the mixture heated at reflux
under an argon atmosphere for 90 min, at which time full conversion
NMR (400 MHz, CDCl3): δ 5.82 (ddd, J2−1trans = 17.2 Hz, J2−1cis
=
1
to aldehyde 14 was observed via H NMR spectroscopy. The solvent
10.4 Hz, J2−3 = 5.8 Hz, 1H, H2), 5.65 (dtd, J5−4 = 15.4 Hz, J5−6 = 6.6
Hz, J5−3 = 1.0 Hz, 1H, H5), 5.46 (ddt, J4−5 = 15.4 Hz, J4−3 = 6.6 Hz,
was removed in vacuo and the residue placed on the Schlenk line for
2 h to remove excess crotonaldehyde. The aldehyde product was
unstable to chromatography and was therefore taken directly to the
next step. The residue was taken up in THF (25 mL) and transferred
to a dry addition funnel under an argon atmosphere and added
dropwise to a vinyl Grignard solution (0.34 M in THF, 159 mL,
54 mmol) cooled to −78 °C in a dry ice/acetone bath. Upon complete
addition, the reaction mixture was stirred for an additional 30 min at
−78 °C and then warmed to room temperature. The flask was cooled
again and the reaction quenched with aqueous NH4Cl. This mixture
was extracted with diethyl ether, washed with water and then brine,
and dried over NaSO4. The solvent was removed in vacuo and the
product purified via triethylamine neutralized silica gel chromatog-
raphy with 4:1 hexanes/EtOAc on the bench. The solvent was
removed to yield 3.8 g (80%) of dienol 15 as a clear oil. The product
upon chromatography is spectroscopically pure and sufficient to be
carried forward, while additional chromatography was required to
J4−6 = 1.5 Hz, 1H, H4), 5.18 (dt, J1trans‑2 = 17.3 Hz, J1trans‑1cis = J1trans‑3
=
1.5 Hz, 1H, H1trans), 5.05 (dt, J1cis‑2 = 10.4 Hz, J1cis‑1trans = J1cis‑3 = 1.4
Hz, 1H, H1cis), 4.51 (br app t, J = 6.0 Hz, 1H, H3), 3.87 (m,
4H, -OCH2CH2O−), 2.09 (m, 3H, H6, −OH), 1.68 (m, 2H, H7), 1.26
1
(s, 3H, H8). H−1H GCOSY (400 MHz, CDCl3): δ 5.82 (H2) ↔ δ
5.18 (H1trans), 5.05 (H1cis), 4.51 (H3) ; δ 5.65 (H5) ↔ δ 5.46 (H4),
2.09 (H6); δ 5.46 (H4) ↔ δ 4.51 (H3), 2.09 (H6); δ 5.18 (H1trans) ↔ δ
5.05 (H1cis), 4.51 (H3); δ 5.05 (H1cis) ↔ δ 4.51 (H3); δ 2.09 (H6) ↔ δ
1.68 (H7). 13C{1H} NMR (100 MHz, CDCl3): δ 139.7, 131.9, 131.0,
114.5, 109.6, 73.5, 64.5, 38.2, 26.6, 23.8. Anal. Calcd for C11H18O3: C,
66.64; H, 9.15. Found: C, 66.55; H, 9.14.
−
[Cp*Co(η5-1-(dimethyl-2-ethylmalonyl)pentadienyl)]+BF4
(21). In the drybox, Cp*Co(C2H4)2 (0.94 g, 3.75 mmol) was dissolved
in acetone (15 mL) and placed in a Schlenk tube equipped with a stir
bar and septum. The sealed flask was removed to the Schlenk line and
cooled to −78 °C in a dry ice/acetone bath, and HBF4·Et2O (517 μL,
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Organometallics 2015, 34, 3335−3357

Organometallics
Article
3.75 mmol) was added. Upon addition of HBF4, an immediate color
change from red to black was observed. The reaction mixture was
stirred under argon for 15 min, then (E)-dimethyl 2-(hepta-1,4-diene-
3-ol)malonate (1.00 g, 4.13 mmol) was added via syringe ,and the
reaction mixture was warmed to room temperature overnight. A
gradual color change from black to red occurred. The solvent was
removed in vacuo and the product purified on the bench by silica gel
chromatography using 3% MeOH/CH2Cl2. The red fraction was
collected and dried to yield 1.61 g (85%) of product as a red oil. IR
(neat, cm−1): 3539 (w), 2956 (m), 2853 (w), 1731 (s), 1639 (w),
1438 (s), 1382 (w), 1260 (s), 1158 (s), 1078 (w), 1012 (m), 908 (w),
calculated for C24H34O4Co (M+ − BF4) 445.17836, found 445.17834
(100%).
[Cp*Co(η2,η3-1-(dimethyl-2-propylmalonyl)cycloheptadienyl)]+BF4−
(24). Pentadienyl complex 22 (827 mg, 1.59 mmol) was dissolved in
CH2Cl2 (10 mL) and degassed with argon for 5 min. Simultaneously,
acetylene was bubbled through CH2Cl2 in a test tube for 25 min in
order to ensure saturation. Then, 15 mL of this saturated solution was
transferred to the bomb via cannula. The bomb was sealed and allowed
to stand at room temperature for 3 days. The solvent was removed in
vacuo and the product purified by silica gel chromatography using 3%
MeOH/CH2Cl2. The red fraction was collected and dried, providing
702 mg (81%) of product as a thick, red oil. Crystallization via two-
chambered liquid diffusion using CH2Cl2 and Et2O provided red
crystals suitable for combustion and X-ray analysis. IR (CH2Cl2
cast, cm−1): 2955 (m), 2863 (w), 1732 (s), 1653 (w), 1457 (m),
1436 (m), 1388 (m), 1282 (m), 1220 (m), 1156 (m), 1054 (s), 891
875 (w), 843 (s). 1H NMR (400 MHz, CDCl3): δ 6.31 (t, J3−2 = J3−4
=
7.0 Hz, 1H, H3), 5.07 (dd, J4−5 = 11.7 Hz, J4−3 = 6.9 Hz, 1H, H4), 4.96
(ddd, J2−1anti = 11.7 Hz, J2−3 = 9.8 Hz, J2−1syn = 9.6 Hz, 1H, H2), 3.74
(s, 3H, −OMe), 3.72 (s, 3H, −OMe), 3.42 (t, J8−7 = 7.0 Hz, 1H, H8),
3.21 (dd, J1syn‑2 = 9.6 Hz, J1syn‑1anti = 3.4 Hz, 1H, H1syn), 2.16−2.03 (m,
2H), 1.99 (m, 2H), 1.82 (s, 15H, C5Me5), 1.77 (dd, J1anti‑2 = 12.5 Hz,
J1anti‑1syn = 3.9 Hz, 1H, H1anti), 1.50 (m, 1H). 13C{1H} NMR (100
MHz, CDCl3): δ 169.3, 99.6, 99.0, 98.6, 95.3, 64.4, 52.6, 50.3, 30.3,
29.4, 9.6. Electrospray MS: m/z calculated for C22H32O4Co (M+ −
BF4) 419.16271, found 419.16223 (100%). Anal. Calcd for
C22H32O4CoBF4: C, 52.20; H, 6.37. Found: C, 52.29; H, 6.52.
1
(w), 796 (w), 732 (m). H NMR (400 MHz, CDCl3): δ 3.96 (td,
J3−2 = J3−4endo = 8.4 Hz, J3−4‑exo = 4.0 Hz, 1H, H3), 3.73 (s, 6H,
−OMe), 3.58 (dd, J1−2 = 7.6 Hz, J1−7 = 3.8 Hz, 1H, H1), 3.41 (t,
J11−10 = 7.5 Hz, 1H, H11), 3.34 (t, J2−1 = J2−3 = 7.6 Hz, 1H, H2), 3.15
(dt, J4endo−4exo = 14.3 Hz, J4endo−3 = J4endo−5 = 8.7 Hz, 1H, H4endo), 2.87
(td, J5−4endo = J5−6 = 7.1 Hz, J5−4exo = 5.4 Hz, 1H, H5), 2.36 (dd, J6−5
=
−
[Cp*Co(η5-1-(dimethyl-2-propylmalonyl)pentadienyl)]+BF4
6.3 Hz, J6−7 = 4.7 Hz, 1H, H6), 2.18 (tt, J7−8 = 8.0 Hz, J7−1 = J7−6 = 3.7
Hz, 1H, H7), 2.10 (dt, J4exo−4endo = 14.4 Hz, J4exo−3 = J4exo−5 = 4.1 Hz,
1H, H4exo), 1.93 (q, J10−9 = J10−11 = 7.7 Hz, 2H, H10), 1.88−1.79 (m,
2H, H8, overlaps Cp* peak), 1.82 (s, 15H, C5Me5), 1.44 (m, 2H, H9).
1H−1H GCOSY (400 MHz, CDCl3): δ 3.96 (H3) ↔ δ 3.34 (H2), 3.15
(H4endo), 2.10 (H4exo); δ 3.58 (H1) ↔ δ 3.34 (H2), 2.18 (H7); δ 3.41
(H11) ↔ δ 1.93 (H10); δ 3.15 (H4endo) ↔ δ 2.87 (H5), 2.10 (H4exo); δ
2.87 (H5) ↔ δ 2.36 (H6), 2.10 (H4exo); δ 2.36 (H6) ↔ δ 2.18 (H7); δ
2.18 (H7) ↔ δ 1.88−1.79 (H8); δ 1.93 (H10) ↔ δ 1.44 (H9). 13C{1H}
NMR (100 MHz, CDCl3): δ 169.6, 97.7, 92.2, 53.5, 52.5, 51.1, 49.8,
45.9, 44.7, 33.5, 31.8, 28.2, 23.7, 21.6, 9.6. Electrospray MS: m/z
calculated for C25H36O4Co (M+ − BF4) 459.19401, found 459.19432
(100%). Anal. Calcd for C25H36O4CoBF4: C, 54.97; H, 6.64. Found:
C, 54.52; H, 6.64.
(22). In the drybox, Cp*Co(C2H4)2 (0.720 g, 2.88 mmol) was
dissolved in acetone (10 mL) and placed in a Schlenk tube equipped
with a stir bar and septum. The sealed flask was removed from the
Schlenk line and cooled to −78 °C in a dry ice/acetone bath, and
HBF4·Et2O (397 μL, 2.88 mmol) was added. Upon addition of HBF4,
an immediate color change from red to black was observed. The
reaction mixture was stirred under argon for 15 min, then (E)-
dimethyl-2-(octa-1,4-diene-3-ol)malonate (0.813 g, 3.17 mmol) was
added via syringe, and the reaction mixture was warmed to room
temperature overnight. A gradual color change from black to red
occurred. The solvent was removed in vacuo and the product purified
on the bench by silica gel chromatography using 3% MeOH/CH2Cl2.
The red fraction was collected and dried to yield 1.20 g (80%) of
product as a red oil. Spectroscopy was not successful due to slow
decomposition; therefore, this product was carried forward without
further characterization.
−
[Cp*Co(η5-1-(dimethyl-2-ethylmalonyl)cycloheptadienyl)]+BF4
(25). Allyl/olefin complex 23 (10 mg) was dissolved in CH2Cl2
(5 mL) in a reaction bomb and heated at 60 °C in an oil bath for
3 days. The solvent was removed and the residue filtered through silica
−
[Cp*Co(η2,η3-1-(dimethyl-2-ethylmalonyl)cycloheptadienyl)]+BF4
1
(23). Pentadienyl complex 21 (127 mg, 0.25 mmol) was dissolved in
CH2Cl2 (10 mL) and degassed with argon for 5 min. Simultaneously,
acetylene was bubbled through CH2Cl2 in a test tube for 25 min in
order to ensure saturation. Then, 2 mL of this saturated solution was
transferred to the bomb via cannula. The bomb was sealed and allowed
to stand at room temperature for 3 days. The solvent was removed in
vacuo and the product purified by silica gel chromatography using 3%
MeOH/CH2Cl2. The red fraction was collected and dried, providing
119 mg (89%) of product as a thick, red oil. Crystallization via two-
chambered liquid diffusion using CH2Cl2 and Et2O provided red
crystals suitable for combustion analysis. IR (CH2Cl2 cast, cm−1): 2957
(m), 2919 (w), 2865 (w), 1732 (s), 1455 (m), 1436 (m), 1389 (m),
1346 (w), 1285 (m), 1225 (m), 1153 (m), 1056 (s), 798 (w), 732 (w).
1H NMR (400 MHz, CDCl3): δ 3.92 (td, J3−2 = J3−4endo = 8.3 Hz,
J3−4exo = 4.1 Hz, 1H, H3), 3.71 (s, 3H, −OMe), 3.70 (s, 3H, −OMe),
3.60 (dd, J1−2 = 7.6 Hz, J1−7 = 3.8 Hz, 1H, H1), 3.41 (t, J10−9 = 6.9 Hz,
gel using 3% MeOH/CH2Cl2 to remove paramagnetic impurities. H
NMR spectroscopy indicated quantitative conversion to the fully
conjugated isomer. The spectra were identical with those previously
reported.22
−
[Cp*Co(η5-1-(dimethyl-2-propylmalonyl)cycloheptadienyl)]+BF4
(26). Allyl/olefin complex 24 (10 mg) was dissolved in CH2Cl2
(5 mL) in a reaction bomb and heated at 60 °C in an oil bath for
3 days. The solvent was removed and the residue filtered through silica
1
gel using 3% MeOH/CH2Cl2 to remove paramagnetic impurities. H
NMR spectroscopy indicated quantitative conversion to the fully
conjugated isomer. The spectra were identical with those previously
reported.22
[Cp*Co(η5-1,2-dimethyl-7-(dimethyl-2-ethylmalonyl)-
−
cycloheptadienyl)]+BF4 (27). Pentadienyl complex 21 (311 mg,
0.62 mmol) was dissolved in CH2Cl2 (10 mL) in a reaction bomb and
degassed with argon for 5 min. To this was added 2-butyne (325 μL,
4.15 mmol) via syringe. The bomb was sealed and heated at 40 °C for
3 days in an oil bath. The solvent was then removed in vacuo and the
product purified by silica gel chromatography using 3% MeOH/
CH2Cl2. The red fraction was collected and dried, providing 241 mg
(70%) of product as a thick, red oil. Crystallization via two-chambered
liquid diffusion using CH2Cl2 and Et2O provided red crystals suitable
for combustion analysis. IR (CH2Cl2 cast, cm−1): 2956 (m), 2909 (m),
1732 (s), 1435 (s), 1384 (m), 1345 (w), 1268 (m), 1239 (m), 1199
1H, H10), 3.30 (t, J2−1 = J2−3 = 7.6 Hz, 1H, H2), 3.10 (dt, J4endo−4exo
14.1 Hz, J4endo−3 = J4endo−5 = 8.5 Hz, 1H, H4endo), 2.83 (td, J5−4endo
J5−6 = 7.3 Hz, J5−4exo = 4.9 Hz, 1H, H5), 2.42 (dd, J6−5 = 6.6 Hz, J6−7
=
=
=
4.5 Hz, 1H, H6), 2.16 (tt, J7−8 = 7.6 Hz, J7−1 = J7−6 = 3.7 Hz, 1H, H7),
2.04 (dt, J4exo−4endo = 14.1 Hz, J4exo−3 = J4exo−5 = 4.3 Hz, 1H, H4exo),
1.90 (m, 2H, H9), 1.82−1.78 (m, 2H, H8, overlaps Cp* peak), 1.77 (s,
15H, C5Me5). 1H−1H GCOSY (400 MHz, CDCl3): δ 3.92 (H3) ↔ δ
3.60 (H1), 3.30 (H2), 3.10 (H4endo), 2.04 (H4exo); δ 3.60 (H1) ↔ δ
3.30 (H2), 2.16 (H7); δ 3.41 (H10) ↔ δ 1.90 (H9); δ 3.30 (H2) ↔ δ
2.04 (H4exo); δ 3.10 (H4endo) ↔ δ 2.83 (H5), 2.42 (H6), 2.04 (H4exo);
δ 2.83 (H5) ↔ δ 2.42 (H6), 2.04 (H4exo); δ 2.42 (H6) ↔ δ 2.16 (H7);
δ 2.16 (H7) ↔ δ 1.82−1.78 (H8); δ 1.90 (H9) ↔ δ 1.82−1.78 (H8).
13C{1H} NMR (100 MHz, CDCl3): δ 169.5, 97.8, 92.2, 53.1, 52.6,
50.8, 49.3, 45.8, 44.5, 31.9, 31.1, 25.3, 21.4, 9.5. Electrospray MS: m/z
1
(m), 1150 (m), 1054 (s), 910 (w), 864 (w), 732 (m), 700 (m). H
NMR (600 MHz, CDCl3): δ 6.59 (d, J1−2 = 7.4 Hz, 1H, H1), 4.69
(t, J2−1 = J2−3 = 8.4 Hz, 1H, H2), 4.36 (dt, J3−2 = 9.1 Hz, J3−4endo
J3−4exo = 3.3 Hz, 1H, H3), 3.71 (s, 3H, −OMe), 3.70 (s, 3H, −OMe),
3.21 (t, J8−7 = 7.1 Hz, 1H, H8), 2.48 (ddd, J4endo−4exo = 16.7 Hz, J4endo−5
=
=
11.9 Hz, J4endo−3 = 2.8 Hz, 1H, H4exo), 2.34 (dt, J4exo−4endo = 16.7 Hz,
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J4exo−3 = J4exo−5 = 3.1 Hz, 1H, H4exo), 2.22 (s, 3H, Me), 1.75 (s, 15H,
C5Me5), 1.61 (m, 1H, H7), 1.48 (dddd, J7′‑7 = 18.7 Hz, J7′‑6 = 11.8 Hz,
J7′‑8 = 7.2 Hz, J7′‑6′ = 4.5 Hz, 1H, H7′), 1.35 (tt, J6−6′ = J6−7′ = 12.3 Hz,
(dtd, J6′‑6 = 12.5 Hz, J6′‑5 = J6′‑7 = 10.2 Hz, J6′‑7′ = 5.5 Hz, 1H, H6′), 1.30
1
(s, 3H, Me). H−1H GCOSY (400 MHz, CDCl3): δ 6.46 (H3) ↔ δ
5.13 (H4), 5.03 (H2), 3.20 (H1syn), 1.96 (H5), 1.65 (H1anti); δ 5.13
(H4) ↔ δ 1.96 (H5); δ 5.03 (H2) ↔ δ 3.20 (H1syn), 1.65 (H1anti); δ
3.20 (H1syn) ↔ δ 1.65 (H1anti); δ 2.10 (H6) ↔ δ 1.96 (H5), 1.70 (H7),
1.56 (H6′); δ 1.96 (H5) ↔ δ 1.56 (H6′); δ 1.70 (H7) ↔ δ 1.56 (H6′).
13C{1H} NMR (100 MHz, CDCl3): δ 109.3, 99.87, 99.29, 98.7, 95.7,
87.8, 65.0, 64.9, 64.2, 40.2, 28.1, 24.2, 10.0. Electrospray MS: m/z
calculated for C21H32O2Co (M+ − BF4) 375.17288, found 375.17293
(100%). Anal. Calcd for C21H32O2CoBF4: C, 54.57; H, 6.98. Found:
C, 54.46; H, 7.02.
J6−5 = J6−7 = 5.0 Hz, 1H, H6), 1.29 (s, 3H, Me), 1.23 (tdd, J6′‑6 = J6′‑7
13.4 Hz, J6′‑5 = 9.0 Hz, J6′‑7′ = 5.2 Hz, 1H, H6′), 0.02 (ddt, J5−14endo
=
=
12.8 Hz, J5−6′ = 9.3 Hz, J5−4exo = J5−6 = 4.7 Hz, 1H, H5). H−1H
GCOSY (600 MHz, CDCl3): δ 6.59 (H1) ↔ δ 4.69 (H2); δ 4.69
(H2) ↔ δ 4.36 (H3); δ 4.36 (H3) ↔ δ 2.48 (H4endo), 2.34 (H4exo); δ
3.21 (H8) ↔ δ 1.61 (H7), 1.48 (H7′); δ 2.48 (H4endo) ↔ δ 2.34
(H4exo), 0.02 (H5); δ 2.34 (H4exo) ↔ δ 0.02 (H5); δ 1.61 (H7) ↔ δ
1.48 (H7′), 1.35 (H6), 1.23 (H6′); δ 1.48 (H7′) ↔ δ 1.35 (H6), 1.23
(H6′); δ 1.35 (H6) ↔ δ 1.23 (H6′), 0.02 (H5); δ 1.23 (H6′) ↔ δ 0.02
(H5). 13C{1H} NMR (100 MHz, CDCl3): δ 169.4, 108.7, 100.9, 99.1,
97.7, 96.1, 86.6, 52.6, 51.3, 47.9, 41.7, 28.2, 28.0, 19.2, 17.0, 9.0.
Electrospray MS: m/z calculated for C26H38O4Co (M+ − BF4)
473.20966, found 473.20964 (100%). Anal. Calcd for
C26H38O4CoBF4: C, 55.73; H, 6.84. Found: C, 55.48; H, 7.20.
[Cp*Co(η5-1,2-dimethyl-7-(dimethyl-2-propylmalonyl)-
−
[Cp*Co(η5-1-(3-butanoyl)pentadienyl)]+BF4 (30). Protected
pentadienyl complex 29 (52 mg, 0.11 mmol) was placed in a round-
bottom flask equipped with a reflux condenser and dissolved in off-the-
shelf acetone (15 mL). To this was added HBF4·OEt2 (10 μL) and the
mixture was heated at reflux overnight (∼16 h). The solvent was
removed in vacuo and the residue purified via benchtop silica gel
chromatography using 3% MeOH/CH2Cl2 to provide 38 mg (81%) of
deprotected pentadienyl complex 30. Crystallization via two-
chambered liquid diffusion using CH2Cl2 and Et2O provided red
crystals suitable for combustion and X-ray analysis. IR (neat, cm−1):
2923 (m), 1709 (s), 1460 (m), 1428 (m), 1391 (m), 1366 (w), 1285
(w), 1270 (m), 1184 (w), 1165 (m), 1054 (s), 951 (w), 920 (w), 895
−
cycloheptadienyl)]+BF4 (28). Pentadienyl complex 22 (53 mg,
0.10 mmol) was dissolved in CH2Cl2 (10 mL) in a reaction bomb and
degassed with argon for 5 min. To this was added 2-butyne (50 μL,
0.64 mmol) via syringe. The bomb was sealed and heated at 40 °C for
3 days in an oil bath. The solvent was then removed in vacuo and
the product purified by silica gel chromatography using 3%
MeOH/CH2Cl2. The red fraction was collected and dried, providing
54 mg (93%) of product as a thick, red oil. Crystallization was
unsuccessful for obtaining analytically pure material despite multiple
attempts, due to the oily nature of the product. IR (CH2Cl2 cast, cm−1):
2955 (m), 1732 (s), 1436 (m), 1384 (m), 1276 (m), 1232 (m), 1152
(w), 817 (w), 736 (w). 1H NMR (400 MHz, CDCl3): δ 6.33 (t, J3−2
=
J3−4 = 7.0 Hz, 1H, H3), 5.18 (dd, J4−5 = 11.9 Hz, J4−3 = 6.8 Hz, 1H,
H4), 4.98 (ddd, J2−1anti = 11.5 Hz, J2−1syn = 9.8 Hz, J2−3 = 7.2 Hz, 1H,
H2), 3.18 (dd, J1syn‑2 = 9.6 Hz, J1syn‑1‑anti = 3.5 Hz, 1H, H1syn), 2.65 (t,
J7−6 = J7−6′ = 6.9 Hz, 2H, H7), 2.28 (dtd, J6−6′ = 17.0 Hz, J6−7 = 6.9 Hz,
J6−5 = 4.0 Hz, 1H, H6), 2.08 (s, 3H, Me), 2.01 (m, 1H, H5), 1.84 (s,
15H, C5Me5), 1.80 (dd, J1anti‑2 = 11.8 Hz, J1anti‑1syn = 3.3 Hz, 1H,
H1anti), 1.69 (m, 1H, H6′). 1H−1H GCOSY (400 MHz, CDCl3): δ 6.33
(H3) ↔ δ 5.18 (H4), 4.98 (H2), 318 (H1syn), 2.01 (H5), 1.80 (H1anti); δ
5.18 (H4) ↔ δ 2.01 (H5); δ 4.98 (H2) ↔ δ 3.18 (H1syn), 1.80 (H1anti);
δ 3.18 (H1syn) ↔ δ 1.80 (H1anti); δ 2.65 (H7) ↔ δ 2.28 (H6), 1.69
(H6′); δ 2.28 (H6) ↔ δ 2.01 (H5), 1.69 (H6′); δ 2.01 (H5) ↔ δ 1.69
(H6′). 13C{1H} NMR (100 MHz, CDCl3): δ 207.4, 99.7, 99.3, 98.4,
95.2, 86.3, 64.3, 43.6, 30.0, 26.9, 9.7. Electrospray MS: m/z calculated
for C19H28OCo (M+ − BF4): 331.14666, found 331.14672 (100%).
Anal. Calcd for C19H28OCoBF4: C, 54.57; H, 6.75. Found: C, 54.56;
H, 6.91.
1
(m), 1056 (s), 909 (w), 733 (m). H NMR (400 MHz, CDCl3): δ
6.58 (d, J1−2 = 7.3 Hz, 1H, H1), 4.68 (t, J2−1 = J2−3 = 8.5 Hz, 1H, H2),
4.34 (dt, J3−2 = 9.3 Hz, J3−4endo = J3−4exo = 3.1 Hz, 1H, H3), 3.69 (s,
3H, −OMe), 3.68 (s, 3H, −OMe), 3.23 (t, J9−8 = 7.4 Hz, 1H, H9),
2.42 (ddd, J4endo−4exo = 16.9 Hz, J4endo−5 = 11.7 Hz, J4endo−3 = 2.9 Hz,
1H, H4endo), 2.30 (dt, J4exo−4endo = 17.1 Hz, J4exo−3 = J4exo−5 = 3.6 Hz,
1H, H4exo), 2.20 (s, 3H, Me), 1.90−1.70 (m, 2H, H8, overlaps Cp*
peak), 1.74 (s, 15H, C5Me5), 1.38−1.19 (m, 2H, H6, overlaps Me
peak), 1.26 (s, 3H, Me), 1.07 (m, 1H, H7), 0.88 (m, 1H, H7′), 0.00 (m,
1H, H5). 1H−1H GCOSY (400 MHz, CDCl3): δ 6.58 (H1) ↔ δ 4.68
(H2); δ 4.68 (H2) ↔ δ 4.34 (H3); δ 4.34 (H3) ↔ δ 2.42 (H4endo), 2.30
(H4exo); δ 3.23 (H9) ↔ δ 1.90−1.70 (H8); δ 2.42 (H4endo) ↔ δ 2.30
(H4exo), 0.00 (H5); δ 2.30 (H4exo) ↔ δ 0.00 (H5); δ 1.90−1.70 (H8) ↔
δ 1.07 (H7), 0.88 (H7′); δ 1.38−1.19 (H6) ↔ δ 1.07 (H7), 0.88 (H7′),
0.00 (H5); δ 1.07 (H7) ↔ δ 0.88 (H7′). 13C{1H} NMR (100 MHz,
CDCl3): δ 169.5, 108.6, 101.0, 99.2, 97.5, 96.3, 86.8, 52.4, 51.2, 48.0,
41.3, 30.3, 28.5, 26.5, 19.1, 16.9, 9.0. Electrospray MS: m/z calculated
for C27H40O4Co (M+ − BF4) 487.22531, found 487.22550 (100%).
−
[Cp*Co(η2,η3-1-(3-butanoyl)cycloheptadienyl)]+BF4 (31).
Pentadienyl complex 30 (141 mg, 0.34 mmol) was dissolved in
CH2Cl2 (10 mL) and degassed with argon for 5 min. Simultaneously,
acetylene was bubbled through CH2Cl2 in a test tube for 25 min in
order to ensure saturation. Then, 3 mL of this saturated solution was
transferred to the bomb via cannula. The bomb was sealed and allowed
to stand at room temperature for 3 days. The solvent was removed in
vacuo and the product purified by silica gel chromatography using 3%
MeOH/CH2Cl2. The red fraction was collected and dried, providing
131 mg (88%) of product as a thick, red oil. Crystallization via two-
chambered liquid diffusion using CH2Cl2 and Et2O provided red
crystals suitable for combustion and X-ray analysis. IR (CH2Cl2 cast,
cm−1): 2919 (m), 1711 (s), 1454 (m), 1428 (m), 1384 (s), 1284 (w),
−
[Cp*Co(η5-1-(3-butanoyl acetal)pentadienyl]+BF4 (29). In
the drybox, Cp*Co(C2H4)2 (192 mg, 0.77 mmol) was dissolved in
acetone (5 mL) and placed in a Schlenk tube equipped with a stir bar
and septum. The sealed flask was removed from the Schlenk line and
cooled to −78 °C in a dry ice/acetone bath, and HBF4·Et2O (105 μL,
0.77 mmol) was added. Upon addition of HBF4, an immediate color
change from red to black was observed. The reaction mixture was
stirred under argon for 15 min, then (E)-nona-1,4-dien-3-ol-8-acetal
(163 mg, 0.82 mmol) was added via syringe, and the reaction mixture
was warmed to room temperature overnight. A gradual color change
from black to red occurred. The solvent was removed in vacuo and the
product purified on the bench by silica gel chromatography using 3%
MeOH/CH2Cl2. The red fraction was collected and dried to yield
289 mg (81%) of product as a red oil. Crystallization via two-
chambered liquid diffusion using CH2Cl2 and Et2O provided a red
powder suitable for combustion analysis. IR (neat, cm−1): 2981 (w),
1453 (w), 1430 (w), 1383 (w), 1222 (w), 1053 (s), 950 (w), 904 (w),
863 (w). 1H NMR (400 MHz, CDCl3): δ 6.46 (t, J3−2 = J3−4 = 6.9 Hz,
1H, H3), 5.13 (dd, J4−5 = 11.9 Hz, J4−3 = 6.8 Hz, 1H, H4), 5.03 (ddd,
J2−1anti = 11.8 Hz, J2−1syn = 9.7 Hz, J2−3 = 7.1 Hz, 1H, H2), 3.94 (m, 4H,
−OCH2CH2O−), 3.20 (dd, J1syn‑2 = 9.5 Hz, J1syn‑1‑anti = 3.4 Hz, 1H,
H1syn), 2.10 (m, 1H, H6), 1.96 (td, J5−4 = J5−6 = 10.7 Hz, J5−6′ = 4.1 Hz,
1H, H5), 1.86 (s, 15H, C5Me5), 1.80−1.70 (m, 3H, H1anti, H7), 1.56
1
1231 (w), 1170 (w), 1056 (s), 895 (w), 846 (w), 798 (w). H NMR
(400 MHz, CDCl3): δ 3.91 (td, J3−2 = J3−4endo = 8.4 Hz, J3−4exo = 4.0
Hz, 1H, H3), 3.69 (dd, J1−2 = 7.5 Hz, J1−7 = 3.7 Hz, 1H, H1), 3.33
(t, J2−1 = J2−3 = 7.6 Hz, 1H, H2), 3.10 (td, J4endo−4exo = 14.1 Hz, J4endo−3
J4endo−5 = 8.4 Hz, 1H, H4endo), 2.86 (td, J5−4endo = J5−6 = 7.2 Hz, J5−4exo
=
=
4.8 Hz, 1H, H5), 2.69 (t, J9−8 = 7.2 Hz, 2H, H9), 2.49 (dd, J6−5 = 6.4 Hz,
J6−7 = 4.6 Hz, 1H, H6), 2.21 (m, 1H, H7, overlaps Me peak), 2.19 (s, 3H,
Me), 2.11 (m, 1H, H4exo, overlaps H8), 2.08 (t, J8−9 = 6.8 Hz, 2H, H8),
1
1.84 (s, 15H, C5Me5). H−1H GCOSY (400 MHz, CDCl3): δ 3.91
(H3) ↔ δ 3.33 (H2), 3.10 (H4endo), 2.11 (H4exo); δ 3.69 (H1) ↔ δ 3.33
(H2), 2.21 (H7); δ 3.33 (H2) ↔ δ 2.21 (H7); δ 3.10 (H4endo) ↔ δ 2.86
(H5), 2.49 (H6), 2.11 (H4exo); δ 2.86 (H5) ↔ δ 2.49 (H6), 2.11 (H4exo);
δ 2.69 (H9) ↔ δ 2.08 (H8); δ 2.49 (H6) ↔ δ 2.21 (H7). 13C{1H} NMR
(100 MHz, CDCl3): δ 208.5, 97.8, 92.2, 53.4, 49.8, 45.8, 44.4, 39.8, 31.6,
30.1, 27.2, 21.6, 9.6. Electrospray MS: m/z calculated for C21H30OCo
(M+ − BF4): 357.16231, found 357.16251 (100%). Anal. Calcd for
C21H30OCoBF4: C, 56.78; H, 6.81. Found: C, 56.69; H, 6.83.
3352
DOI: 10.1021/acs.organomet.5b00346
Organometallics 2015, 34, 3335−3357

Organometallics
Article
[Cp*Co(η5-1-(3-butanoyl)cycloheptadienyl)]+BF4 (32). Allyl/
olefin complex 31 (40 mg, 0.090 mmol) was dissolved in CH2Cl2
(5 mL) in a reaction bomb and heated at 70 °C for 2 days. The solvent
was removed in vacuo and the product purified by silica gel
chromatography to provide 36 mg (90%) of the isomerized product
32 as a red oil. Crystallization via two-chambered liquid diffusion using
CH2Cl2 and Et2O provided red crystals suitable for combustion and
X-ray analysis. IR (neat, cm−1): 3048 (w), 2961 (w), 2919 (w), 2852
(w), 1708 (s), 1489 (w), 1450 (m), 1420 (m), 1388 (m), 1379 (m),
1359 (w), 1318 (w), 1286 (w), 1268 (w), 1227 (w), 1193 (w), 1174
(m), 1154 (m), 1099 (s), 1057 (s), 1038 (s), 964 (m). 1H NMR (400
1322 (w), 1280 (w), 1259 (s), 1236 (m), 1172 (w), 1144 (w), 1093
(s), 1048 (s), 1000 (m), 949 (m), 908 (m), 893 (m). H NMR (400
−
1
MHz, CDCl3): δ 3.95 (s, 4H, −OCH2CH2O−), 3.93 (m, 1H, H3,
overlaps acetal peak), 3.58 (dd, J1−2 = 7.5 Hz, J1−7 = 3.7 Hz, 1H, H1),
3.34 (t, J2−1 = J2−3 = 7.6 Hz, 1H, H2), 3.12 (dt, J4endo−4exo = 14.2 Hz,
J4endo−3 = J4endo−5 = 8.3 Hz, 1H, H4endo), 2.87 (td, J5−4endo = J5−6 = 7.7
Hz, J5−4exo = 4.8 Hz, 1H, H5), 2.36 (dd, J6−5 = 6.2 Hz, J6−7 = 4.8 Hz,
1H, H6), 2.17 (tt, J7−8 = 7.3 Hz, J7−1 = J7−6 = 3.7 Hz, 1H, H7), 2.06 (dt,
J4exo−4endo = 14.1 Hz, J4exo−3 = J4exo−5 = 4.2 Hz, 1H, H4exo), 1.95−1.82
(m, 2H, H8), 1.80 (s, 15H, C5Me5), 1.75−1.64 (m, 2H, H9), 1.30 (s,
3H, Me). 1H−1H GCOSY (400 MHz, CDCl3): δ 3.93 (H3) ↔ δ 3.34
(H2), 3.12 (H4endo), 2.06 (H4exo); δ 3.58 (H1) ↔ δ 3.34 (H2), 2.17
(H7); δ 3.12 (H4endo) ↔ δ 2.87 (H5), 2.06 (H4exo); δ 2.87 (H5) ↔ δ
2.36 (H6), 2.06 (H4exo); δ 2.36 (H6) ↔ δ 2.17 (H7); δ 2.17 (H7) ↔ δ
1.95−1.82 (H8); δ 1.95−1.82 (H8) ↔ δ 1.75−1.64 (H9). 13C{1H}
NMR (100 MHz, CDCl3): δ 109.2, 97.6, 92.2, 64.6, 53.8, 50.3, 46.0,
44.6, 35.2, 31.9, 28.1, 23.8, 21.5, 9.6. Electrospray MS: m/z calculated
for C23H34O2Co (M+ − BF4) 401.18853, found 401.18832 (100%).
Anal. Calcd for C23H34O2CoBF4: C, 56.58; H, 7.02. Found: C, 56.61;
H, 7.17.
MHz, CDCl3): δ 6.63 (t, J3−2 = J3−4 = 6.5 Hz, 1H, H3), 5.34 (t, J2−1
=
J2−3 = 7.2 Hz, 1H, H2), 4.94 (t, J4−3 = J4−5 = 8.3 Hz, 1H, H4), 4.34 (dt,
J5−4 = 9.2 Hz, J5−6endo = J5−6exo = 3.7 Hz, 1H, H5), 4.08 (dd, J1−2 = 8.0
Hz, J1−7 = 3.8 Hz, 1H, H1), 2.45−2.33 (m, 3H, H6endo, H9), 2.11 (s,
3H, Me), 2.06 (br dt, J6exo−6endo = 17.0 Hz, J6exo−5 = J6exo−7 = 3.5 Hz,
1H, H6exo), 1.88 (s, 15H, C5Me5), 1.71−1.51 (m, 2H, H8), 0.56 (br m,
1H, H7). 1H−1H GCOSY (400 MHz, CDCl3): δ 6.63 (H3) ↔ δ 5.34
(H2), 4.94 (H4), 4.08 (H1); δ 5.34 (H2) ↔ δ 4.08 (H1); δ 4.94 (H4)
↔ δ 4.34 (H5); δ 4.34 (H5) ↔ δ 2.35 (H6endo), 2.06 (H6exo); δ 4.08
(H1) ↔ δ 0.56 (H7); δ 2.40 (H9) ↔ δ 1.65 (H8); δ 2.35 (H6endo) ↔ δ
2.06 (H6exo), 0.56 (H7); δ 2.06 (H6exo) ↔ δ 0.56 (H7); δ 1.65 (H8) ↔
δ 0.56 (H7). 13C{1H} NMR (100 MHz, CDCl3): δ 208.3, 100.5, 98.8,
97.9, 97.7, 94.0, 88.4, 46.6, 41.2, 39.3, 30.0, 29.7, 9.7. Electrospray MS:
m/z calculated for C21H30OCo (M+ − BF4) 357.16231, found
357.16208 (100%). Anal. Calcd for C21H30OCoBF4: C, 56.78; H, 6.81.
Found: C, 56.87; H, 6.75.
−
[Cp*Co(η5-1-(3-butanoyl acetal)cycloheptadienyl)]+BF4
(35). Allyl/olefin complex 34 (40 mg, 0.082 mmol) was dissolved in
CH2Cl2 (5 mL) in a reaction bomb and heated at 60 °C for 16 h. The
solvent was removed in vacuo and the product purified by silica gel
chromatography to provide 40 mg of product as an inseparable 2:1
mixture of the isomerized product 35 and the unprotected 32 as a red
oil. IR (neat, cm−1): 2982 (w), 2921 (w), 1456 (w), 1430 (w), 1382
(w), 1311 (w), 1219 (w), 1054 (s), 952 (w), 857 (w). 1H NMR (400
−
[Cp*Co(η5-1,2-dimethyl-7-(3-butanoyl)cycloheptadienyl)]+BF4
(33). Pentadienyl complex 30 (82 mg, 0.20 mmol) was dissolved in
CH2Cl2 (5 mL) in a reaction bomb and degassed with argon for 3 min.
To this was added 2-butyne (100 μL, 1.28 mmol) via syringe. The
bomb was sealed and heated at 40 °C for 3 days in an oil bath. The
solvent was then removed in vacuo and the product purified by silica
gel chromatography using 3% MeOH/CH2Cl2. The red fraction was
collected and dried, providing 74 mg (80%) of product as a thick, red
oil that contained approximately 10% impurity, tentatively charac-
terized as cobaltocenium type products. Crystallization was
unsuccessful for obtaining analytically pure material despite multiple
attempts, due to the oily nature of the product. IR (neat, cm−1): 2965
(w), 2912 (w), 1711 (s), 1455 (m), 1432 (m), 1384 (s), 1282 (w),
1163 (w), 1054 (s), 910 (w), 865 (w). 1H NMR (400 MHz, CDCl3):
δ 6.49 (d, J1−2 = 7.3 Hz, 1H, H1), 4.60 (t, J2−1 = J2−3 = 7.8 Hz, 1H, H2),
4.34 (dt, J3−2 = 9.1 Hz, J3−4endo = J3−4exo = 3.3 Hz, 1H, H3), 2.45 (ddd,
J4endo−4exo = 16.7 Hz, J4endo−5 = 11.8 Hz, J4endo−3 = 3.0 Hz, 1H, H4endo),
2.25 (dt, J4exo−4endo = 16.6 Hz, J4exo−3 = J4exo−5 = 3.2 Hz, 1H, H4exo),
2.19 (s, 3H, Me), 2.15 (m, 1H, H7), 2.10 (m, 1H, H7′), 2.01 (s, 3H,
Me), 1.73 (s, 15H, C5Me5), 1.61 (m, 1H, H6), 1.45 (m, 1H, H6′), 1.30
(s, 3H, Me), −0.01 (tt, J5−4endo = J5−6 = 9.7 Hz, J5−4exo = J5−6′ = 4.5 Hz,
1H, H5). 1H−1H GCOSY (400 MHz, CDCl3): δ 6.49 (H1) ↔ δ 4.60
(H2); δ 4.60 (H2) ↔ δ 4.34 (H3); δ 4.34 (H3) ↔ δ 2.45 (H4endo), 2.25
MHz, CDCl3): δ 6.64 (t, J3−2 = J3−4 = 6.3 Hz, 1H, H3), 5.30 (t, J2−1
=
J2−3 = 7.4 Hz, 1H, H2), 4.94 (t, J4−3 = J4−5 = 7.9 Hz, 1H, H4), 4.34 (dt,
J5−4 = 8.6 Hz, J5−6endo = J5−6exo = 4.0 Hz, 1H, H5), 4.00 (ddd, J1−2 = 8.2
Hz, J1−7 = 4.1 Hz, J1−3 = 1.0 Hz, 1H, H1), 3.89 (m, 4H, −OCH2CH2O−),
2.32 (ddd, J6endo−6exo = 16.6 Hz, J6endo−7 = 9.6 Hz, J6endo−5 = 4.7 Hz, 1H,
H6endo), 2.02 (dt, J6exo−6endo = 16.5 Hz, J6exo−5 = J6exo−7 = 3.7 Hz, 1H,
H6exo), 1.86 (s, 15H, C5Me5), 1.55−1.35 (m, 4H, H8, H9), 1.24 (s, 3H,
1
Me), 0.57 (m, 1H, H7). H−1H GCOSY (400 MHz, CDCl3): δ 6.64
(H3) ↔ δ 5.30 (H2), 4.94 (H4), 4.00 (H1); δ 5.30 (H2) ↔ δ 4.00
(H1); δ 4.94 (H4) ↔ δ 4.34 (H5); δ 4.34 (H5) ↔ δ 2.32 (H6endo), 2.02
(H6exo); δ 4.00 (H1) ↔ δ 0.57 (H7); δ 2.32 (H6endo) ↔ δ 2.02 (H6exo),
0.57 (H7); δ 2.02 (H6exo) ↔ δ 0.57 (H7); δ 1.52 (H8) ↔ δ 1.38
(H8′ and 9), 0.57 (H7); δ 1.38 (H8′) ↔ δ 0.57 (H7). 13C{1H} NMR
(100 MHz, CDCl3): δ 109.3, 100.6, 98.8, 97.8, 97.7, 94.4, 88.6, 64.7,
46.5, 40.0, 37.0, 30.5, 23.8, 9.7. Electrospray MS: m/z calculated for
C23H34O2Co (M+ − BF4) 401.18853, found 401.18860 (100%).
[Cp*Co(η5 -1,2-dimethyl-7-(3-butanoyl acetal)-
−
cycloheptadienyl)]+BF4 (36). Pentadienyl complex 29 (101 mg,
0.22 mmol) was dissolved in CH2Cl2 (5 mL) in a reaction bomb and
degassed with argon for 5 min. To this was added 2-butyne (100 μL,
1.28 mmol) via syringe. The bomb was sealed and heated at 40 °C for
3 days in an oil bath. The solvent was then removed in vacuo and the
product purified by silica gel chromatography using 3% MeOH/
CH2Cl2. The red fraction was collected and dried, providing 85 mg
of a thick, red oil as an inseparable mixture of product 36 and the
unprotected 33 in a 2:1 ratio. Crystallization was unsuccessful for
obtaining analytically pure material despite multiple attempts, due to
the oily nature of the product. IR (neat, cm−1): 2878 (m), 1457 (m),
1434 (m), 1382 (m)m, 1253 (w), 1213 (m), 1138 (w), 1025 (s), 952
(H4exo); δ 2.45 (H4endo) ↔ δ 2.25 (H4exo), −0.01 (H5); δ 2.25 (H4exo
)
↔ δ −0.01 (H5); δ 2.15 (H7) ↔ δ 2.10 (H7′), 1.61 (H6), 1.45 (H6′); δ
2.10 (H7′) ↔ δ 1.61 (H6), 1.45 (H6′); δ 1.61 (H6) ↔ δ 1.45 (H6′),
−0.01 (H5); δ 1.45 (H6′) ↔ δ −0.01 (H5). 13C{1H} NMR (100 MHz,
CDCl3): δ 208.2, 108.6, 101.2, 99.1, 97.7, 96.2, 86.8, 47.7, 42.5, 41.2,
30.1, 24.3, 19.4, 17.1, 9.1. Electrospray MS: m/z calculated for
C23H34OCo (M+ − BF4) 385.19362, found 385.19380 (100%).
(s), 908 (w), 854 (s). 1H NMR (400 MHz, CDCl3): δ 6.55 (d, J1−2
=
−
[Cp*Co(η2,η3-1-(3-butanoyl)cycloheptadienyl)]+BF4 (34).
Pentadienyl complex 29 (40 mg, 0.087 mmol) was dissolved in
CH2Cl2 (10 mL) and degassed with argon for 5 min. Simultaneously,
acetylene was bubbled through CH2Cl2 in a test tube for 25 min in
order to ensure saturation. Then, 6 mL of this saturated solution was
transferred to the bomb via cannula. The bomb was sealed and allowed
to stand at room temperature for 3 days. The solvent was removed in
vacuo and the product purified by silica gel chromatography using 3%
MeOH/CH2Cl2. The red fraction was collected and dried, providing
34 mg (81%) of product as a thick, red oil. Crystallization via two-
chambered liquid diffusion using CH2Cl2 and Et2O provided red
crystals suitable for combustion and X-ray analysis. IR (neat, cm−1):
3063 (m), 2976 (s), 2930 (s), 1456 (s), 1383 (s), 1372 (s), 1349 (w),
7.2 Hz, 1H, H1), 4.66 (t, J2−1 = J2−3 = 8.7 Hz, 1H, H2, overlaps H2 of
33), 4.35 (dt, J3−2 = 9.2 Hz, J3−4endo = J3−4exo = 3.4 Hz, 1H, H3, overlaps
H3 of 33), 3.85 (m, 4H, -OCH2CH2O−), 2.45 (ddd, J4endo−4exo = 16.8
Hz, J4endo−5 = 12.2 Hz, J4endo−3 = 3.2 Hz, 1H, H4endo, overlaps H4endo of
33), 2.30 (dt, J4exo−4endo = 16.8 Hz, J4exo−5 = J4exo−3 = 3.6 Hz, 1H,
H4exo), 2.20 (s, 3H, Me), 1.74 (s, 15H, C5Me5), 1.39−1.14 (m, 4H, H6,
H7, overlaps Me signals), 1.30 (s, 3H, Me), 1.19 (s, 3H, Me), −0.01
(tt, J5−4endo = J5−6 = 11.8 Hz, J5−4exo = J5−6′ = 4.2 Hz, 1H, H5, overlaps
H5 of 33). 1H−1H GCOSY (400 MHz, CDCl3): δ 6.55 (H1) ↔ δ 4.66
(H2); δ 4.66 (H2) ↔ δ 4.35 (H3); δ 4.35 (H3) ↔ δ 2.45 (H4endo),
2.30 (H4exo); δ 2.45 (H4endo) ↔ δ 2.30 (H4exo), −0.01 (H5); δ
2.30 (H4exo) ↔ δ −0.01 (H5); δ 1.45 (H6) ↔ δ 1.25 (H6′), 1.25
3353
DOI: 10.1021/acs.organomet.5b00346
Organometallics 2015, 34, 3335−3357

Organometallics
Article
(H9), −0.01 (H5); δ 1.25 (H6′) ↔ δ −0.01 (H5). 13C{1H} NMR (100
MHz, CDCl3): δ 108.7, 101.4, 99.2, 97.6, 97.5, 96.3, 86.8, 64.7, 48.2,
41.8, 38.4, 25.0, 23.7, 19.3, 17.0, 9.1. Electrospray MS: m/z calculated
for C25H38O2Co (M+ − BF4) 429.21983, found 429.21965 (100%).
Cp*Co(η2,η2-[5.3.0]-2,2-bis(methylcarboxyl)bicyclodeca-
7,10-diene) (37). Allyl/olefin complex 23 (88 mg, 0.16 mmol) was
dissolved in THF (5 mL) in the glovebox and removed from the
Schlenk line and cooled to −78 °C in a dry ice/acetone bath. To this
3.05 (H4endo) ↔ δ 2.36 (H4exo), 1.96 (H5), 1.53 (H2); δ 2.49
(H10eq) ↔ δ 2.00 (H9eq), 1.65 (H10ax); δ 2.36 (H4exo) ↔ δ 1.96 (H5),
1.53 (H3); δ 1.53 (H2) ↔ δ 1.53 (H3); δ 1.96 (H5) ↔ δ 1.62 (H6); δ
2.02−1.96 (H9eq) ↔ δ 1.70−1.62 (H9ax), 1.35 (H8eq); δ 1.84 (H8ax) ↔
δ 1.40 (H7), 1.35 (H8eq), 1.70−1.62 (H9ax); δ 1.70−1.62 (H9ax) ↔ δ
1.35 (H8eq); δ 1.62 (H6) ↔ δ 1.40 (H7); δ 1.40 (H7) ↔ δ 1.35 (H8eq).
13C{1H} NMR (100 MHz, C6D6): δ 172.5, 170.7, 90.6, 67.0, 66.1,
61.0, 58.0, 51.6, 51.1, 36.5, 34.8, 33.8, 32.6, 29.6, 27.1, 24.4, 9.5.
Electron impact MS: m/z calculated for C25H35O4Co (M+) 458.18674,
found 458.18695 (5%).
solution was added Hunig’s base (28 μL, 0.16 mmol). The reaction
̈
mixture was stirred for 30 min, then the solvent was removed in vacuo
and the residue filtered through activity IV neutral alumina with THF
in the glovebox. The solvent was removed and the product taken up in
a minimal quantity of pentane and cooled to −30 °C. Material slowly
came out of solution, providing 62 mg (88%) of product as a reddish
Cp*Co(η4-[5.4.0]-bicycloundeca-8,10-dien-3-one) (42). Allyl/
olefin complex 32 (108 mg, 0.24 mmol) was dissolved in MeOH
(5 mL) under an argon atmosphere. To this solution was added
pyrrolidine (21 μL, 0.25 mmol), and the mixture was stirred at room
temperature for 16 h. The solvent was removed in vacuo, and the
product was taken up in pentane and filtered through activity IV
neutral alumina in the glovebox. The solvent was removed to yield
47 mg (54%) of product as a red oil. X-ray-quality crystals were
obtained by cooling a concentrated pentane solution to −30 °C in the
1
brown powder. H NMR (400 MHz, C6D6): δ 4.41 (dd, J = 13.2, 3.7
Hz, 1H), 3.41 (s, 3H), 3.38 (s, 3H), 3.35 (m, 1H, obscured by other
signals), 3.05 (dt, J = 14.2, 8.7 Hz, 1H), 2.88 (dt, J = 13.3, 2.7 Hz, 1H),
2.35 (m, 3H), 1.99 (td, J = 7.0, 2.6 Hz, 1H), 1.58 (s, 15H), remaining
signals overlapping or obscured by impurities.
Cp*Co(η4-[5.3.0]-2,2-bis(methylcarboxyl)bicyclodeca-7,10-
diene) (38). Allyl/olefin complex 23 (90 mg, 0.17 mmol) was
dissolved in wet MeOH (5 mL) in the glovebox. To this solution was
added K2CO3 (26 mg, 0.19 mmol). The reaction mixture was stirred
for 16 h, and then the solvent was removed in vacuo and the residue
filtered through Celite with benzene in the glovebox. The solvent was
removed to provide 73 mg (97%) of product as a red oil. Analytically
pure orange crystals were obtained via cooling a saturated pentane
solution to −30 °C. IR (neat, cm−1): 3008 (w), 2986 (w), 2947 (s),
2911 (m), 2859 (m), 2817 (w), 1747 (w), 1724 (s), 1434 (w), 1425
(w), 1376 (w), 1345 (w), 1322 (w), 1262 (m), 1223 (w), 1199 (s),
glovebox. 1H NMR (400 MHz, C6D6): δ 3.95 (dd, J4−5 = 7.0 Hz, J4−3
=
4.5 Hz, 1H, H4), 3.89 (dd, J3−2 = 6.9 Hz, J3−4 = 4.5 Hz, 1H, H3), 2.52
(ddd, J10eq−10ax = 13.4 Hz, J10eq−1 = 3.9 Hz, J10eq−9eq = 2.3 Hz, 1H,
H10eq), 2.15 (ddt, J9eq−9ax = 13.8 Hz, J9eq−8eq = 4.5 Hz, J9eq−8ax = J9eq−10eq
2.4 Hz, 1H, H9eq), 2.09 (t, J5−4 = J5−6endo = 6.8 Hz, 1H, H5), 1.80 (t,
J10ax−10eq = J10ax−1 = 13.0 Hz, 1H, H10ax), 1.74 (td, J9ax−9eq = J9ax−8ax
=
=
13.9 Hz, J9ax−8eq = 6.8 Hz, 1H, H9ax), 1.66 (d, J2−3 = 7.0 Hz, 1H, H2),
1.57 (s, 15H, C5Me5), 1.41 (ddd, J6endo−6exo = 16.2 Hz, J6endo−5 = 6.2
Hz, J6endo−7 = 3.4 Hz, 1H, H6endo), 1.26−1.18 (m, 2H, H1, H8eq), 0.94
(ddd, J6exo−6endo = 16.4 Hz, J6exo−7 = 11.6 Hz, J6exo−5 = 1.7 Hz, 1H,
H6exo), 0.89 (tdd, J8ax−8eq = J8ax− = 13.4 Hz, J8ax−7 = 12.1 Hz, J8ax−9eq
=
1
1152 (m), 1102 (w), 1071 (m), 1050 (w), 1008 (w), 978 (w). H
4.4 Hz, 1H, H8ax, overlaps H6exo), 0.41 (qt, J7−1 = J7−6exo = J7−8ax = 11.7
NMR (300 NMR, C6D6): δ 4.05 (dd, J3−2 = 6.8 Hz, J3−4 = 2194.6 Hz,
1H, H3), 3.97 (dd, J4−5 = 7.1 Hz, J4−3 = 4.6 Hz, 1H, H4), 3.41 (s, 3H,
−OMe), 3.89 (s, 3H, −OMe), 2.65 (d, J2−3 = 6.8 Hz, 1H, H2), 2.49
1
Hz, J7−6endo = J7−8eq = 3.4 Hz, 1H, H7). H−1H GCOSY (400 MHz,
C6D6): δ 3.95 (H4) ↔ δ 3.89 (H3), 2.09 (H5), 1.66 (H2), 1.41
(H6endo); δ 3.89 (H3) ↔ δ 2.09 (H5), 1.66 (H2); δ 2.52 (H10eq) ↔ δ
2.15 (H9eq), 1.80 (H10ax), 1.26−1.18 (H1); δ 2.15 (H9eq) ↔ δ 1.74
(H9ax), 1.26−1.18 (H8eq); δ 2.09 (H5) ↔ δ 1.41 (H6endo), 0.94 (H6exo);
δ 1.80 (H10ax) ↔ δ 1.26−1.18 (H1); δ 1.74 (H9ax) ↔ δ 1.26−1.18
(ddd, J8−8′ = 13.8 Hz, J = 9.2 Hz, J = 7.8 Hz, 1H, H8), 2.17 (dd, J1−7
=
9.9 Hz, J1−2 = 1.5 Hz, 1H, H1), 2.15 (t, J5−4 = J5−6 = 6.9 Hz, 1H, H5),
1.80 (ddd, J8′‑8 = 13.8 Hz, J = 10.9 Hz, J = 3.3 Hz, 1H, H8′), 1.76 (m,
1H, H6′), 1.71 (s, 15H, C5Me5), 1.60 (m, 1H, H9), 1.14−0.94 (m, 3H,
(H8eq), 0.89 (H8ax); δ 1.66 (H2) ↔ δ 1.26−1.18 (H1); δ 1.41 (H6endo
)
1
H6, H7, H9′). H−1H GCOSY (300 MHz, C6D6): δ 4.05 (H3) ↔ δ
↔ δ 0.94 (H6exo), 0.41 (H7); δ 1.26−1.18 (H1) ↔ δ 0.41 (H7); δ
1.26−1.18 (H8eq) ↔ δ 0.89 (H8ax); δ 0.94 (H6exo) ↔ δ 0.41 (H7); δ
0.89 (H8ax) ↔ δ 0.41 (H7). 13C{1H} NMR (100 MHz, C6D6): δ 208.1,
89.8, 81.7, 79.2, 58.0, 52.4, 51.9, 44.7, 41.2, 37.5, 35.5, 33.4, 9.5.
Electron impact MS: m/z calculated for C21H29OCo (M+) 356.15503,
found 356.15547 (51%).
3.97 (H4), 2.65 (H2), 2.15 (H5); δ 3.97 (H4) ↔ δ 2.65 (H2), 2.15
(H5); δ 2.65 (H2) ↔ δ 2.17 (H1); δ 2.49 (H8) ↔ δ 1.80 (H8′), 1.60
(H9), 1.14−0.94 (H9′); δ 2.17 (H1) ↔ δ 1.14−0.94 (H7); δ 2.15 (H5)
↔ δ 1.76 (H6′), 1.14- 0.94 (H6); δ 1.80 (H8′) ↔ δ 1.60 (H9), 1.14−
0.94 (H9′); δ 1.76 (H6′) ↔ δ 1.14−0.96 (H6, H7). 13C{1H} NMR (100
MHz, C6D6): δ 173.0, 171.9, 89.8, 81.5, 81.4, 64.1, 54.1, 53.7, 51.6,
51.5, 50.8, 38.0, 34.9, 31.4, 29.9, 9.5. Electron impact MS: m/z
calculated for C24H33O4Co (M+) 444.17108, found 444.17142
(100%). Anal. Calcd for C24H33O4Co: C, 64.86; H, 7.48. Found: C,
64.84; H, 7.73.
Cp*Co(η2,η2-[5.4.0]-bicycloundeca-7,10-dien-3-one) (43).
Allyl/olefin complex 31 (52 mg, 0.12 mmol) was dissolved in
MeOH (5 mL) under an argon atmosphere. To this solution was
added pyrrolidine (10 μL, 0.12 mmol), and the mixture was stirred at
room temperature for 16 h. The solvent was removed in vacuo, and
the product was taken up in pentane and filtered through activity IV
neutral alumina in the glovebox. The solvent was removed to yield
33 mg (79%) of product as a red oil as a 1:1 mixture with 42 as in-
Cp*Co(η2,η2-[5.4.0]-2,2-bis(methylcarboxyl)bicycloundeca-
7,10-diene) (39). Allyl/olefin complex 24 (48 mg, 0.087 mmol) was
dissolved in MeCN (3 mL) in the glovebox. To this solution
was added NaOMe (5.1 mg, 0.094 mmol). The reaction mixture was
stirred for 15 min, and then the solvent was removed in vacuo and the
residue filtered through activity IV neutral alumina with THF. The
solvent was removed and the product taken up in a minimal quantity
of pentane and cooled to −30 °C. Material slowly came out of
solution, providing 30 mg (76%) of product as a reddish brown
separable isomers. 1H NMR (400 MHz, C6D6): δ 3.16 (dt, J4endo−4exo
13.1 Hz, J4endo−3 = J4endo−5 = 7.7 Hz, 1H, H4endo), 2.95 (dddd, J1−10ax
=
=
13.8 Hz, J1−7 = 9.7 Hz, J1−2 = 4.1 Hz, J1−10eq = 3.1 Hz, 1H, H1), 2.51
(dt, J4exo−4endo = 13.1 Hz, J4exo−3 = J4exo−5 = 2.9 Hz, 1H, H4exo), 2.46 (dt,
J10eq−10ax = 13.7 Hz, J10eq−1 = J10eq−9eq = 2.3 Hz, 1H, H10eq), 2.36 (ddt,
J9eq−9ax = 15.2 Hz, J9eq−8eq = 3.9 Hz, J9eq−8ax = J9eq−10eq = 1.9 Hz, 1H,
powder. 1H NMR (400 MHz, C6D6): δ 3.52 (dd, J1−7 = 10.8 Hz, J1−2
=
H9eq), 2.11 (t, J10ax−10eq = J10ax−1 = 13.7 Hz, 1H, H10ax), 1.92 (td, J5−6
J5−4endo = 7.0 Hz, J5−4exo = 2.6 Hz, 1H, H5), 1.80 (t, J9ax−9eq = J9ax−8ax
=
=
4.0 Hz, 1H, H1), 3.39 (s, 3H, −OMe), 3.32 (s, 3H, −OMe), 3.05
(dt, J4endo−4exo = 13.0 Hz, J4endo−3 = J4endo−5 = 7.8 Hz, 1H, H4endo), 2.49
(m, 1H, H10eq), 2.36 (dt, J4exo−4endo = 13.1 Hz, J4exo−3 = J4exo−5 = 4.4 Hz,
1H, H4exo), 2.00 (dd, J2−3 = 8.1 Hz, J2−1 = 4.1 Hz, 1H, H2), 1.96 (td,
J5−4endo = J5−4exo = 7.2 Hz, J5−4endo = 3.2 Hz, 1H, H5), 2.02−1.92 (m,
1H, H9eq, buried by H2 and H5), 1.84 (m, 1H, H8ax), 1.68 (m, 1H,
H9eq), 1.64 (s, 15H, C5Me5), 1.62 (m, 1H, H6), 1.70−1.62 (m, 1H,
H10ax, buried under Cp* peak), 1.53 (td, J3−2 = J3−4endo = 8.2 Hz, J3−4exo
= 3.0 Hz, 1H, H3), 1.40 (dt, J7−1 = 9.4 Hz, J7−6 = J7−8ax = 2.9 Hz, 1H,
H7), 1.35 (dd, J8eq−8ax = 11.9 Hz, J8eq−9eq = 3.7 Hz, 1H, H8eq). 1H−1H
GCOSY (400 MHz, C6D6): δ 3.52 (H1) ↔ δ 2.00 (H2), 1.40 (H7); δ
15.7 Hz, 1H, H9ax), 1.56 (m, 2H, H6, H8eq, obscured by competing
product), 1.48 (s, 15H, C5Me5), 1.42 (m, 1H, H7, obscured by
competing product), 1.34 (td, J3−2 = J3−4endo = 8.0 Hz, J3−4exo = 2.9 Hz,
1H, H3), 1.23 (m, 1H, H8ax), 1.14 (dd, J2−3 = 7.8 Hz, J2−1 = 4.2 Hz,
1H, H2). 1H−1H GCOSY (400 MHz, C6D6): δ 3.16 (H4endo) ↔ δ 2.51
(H4exo), 1.92 (H5), 1.31 (H3); δ 2.95 (H1) ↔ δ 2.46 (H10eq), 2.11
(H10ax), 1.41 (H7), 1.14 (H2); δ 2.51 (H4exo) ↔ δ 1.91 (H5), 1.31
(H3); δ 2.46 (H10eq) ↔ δ 2.36 (H9eq); δ 2.36 (H9eq) ↔ δ 1.80 (H9ax),
1.56 (H8eq); δ 1.91 (H5) ↔ δ 1.56 (H6); δ 1.80 (H9ax) ↔ δ 1.56
3354
DOI: 10.1021/acs.organomet.5b00346
Organometallics 2015, 34, 3335−3357

Organometallics
Article
(H8eq), 1.23 (H8ax); δ 1.56 (H8eq) ↔ δ 1.42 (H7); δ 1.34 (H3) ↔ δ
1.14 (H2).
isolation of the organic product, followed by a red fraction, shown
to be Cp*Co(η3-CH2CHCH2)Br by comparison with the published
spectra. IR (neat, cm−1): 3008 (w), 2951 (m), 2862 (w), 1730 (s),
1434 (m), 1319 (w), 1252 (s), 1208 (m), 1151 (m), 1110 (w), 1084
(w), 1044 (w), 1035 (w), 1025 (w), 1009 (w), 965 (w), 920 (w), 873
(w), 820 (w), 786 (w), 756 (w), 665 (w). 1H NMR (400 MHz,
CDCl3): δ 5.88−5.76 (m, 2H, H2, H3), 5.62 (dddd, J5−6 = 11.2 Hz,
Cp*Co(η4-[5.4.0]-1,11-dimethylbicycloundeca-8,10-dien-3-
one) (46). Cycloheptadienyl complex 33 (67 mg, 0.14 mmol) was
dissolved in MeOH (5 mL) under an argon atmosphere. To this
solution was added pyrrolidine (12 μL, 0.14 mmol), and the mixture
was stirred at room temperature for 16 h. The solvent was removed in
vacuo, and the product was taken up in pentane and filtered through
activity IV neutral alumina in the glovebox. The solvent was removed
to yield 37 mg (65%) of product as a red oil. Material of improved
purity was obtained via cooling a concentrated pentane solution to
J5−4 = 6.5 Hz, J5−4′ = 4.0 Hz, J5−7 = 2.3 Hz, 1H, H5), 5.28 (dt, J6−5
=
11.4 Hz, J6−4′ = J6−7 = 1.8 Hz, 1H, H6), 3.76 (s, 3H, −OMe), 3.72 (s,
3H, −OMe), 2.90−2.77 (m, 2H, H1, H4), 2.66−2.55 (m, 2H, H4′, H7),
2.35 (dq, J10eq−10ax = 13.2 Hz, J10eq−9eq = J10eq−9ax = J10eq−8eq = 3.1 Hz,
1H, H10eq), 1.87−1.69 (m, 3H, H8eq, H9eq, H10ax), 1.37−1.21 (m, 2H,
H8ax, H9ax). 1H−1H GCOSY (400 MHz, CDCl3): δ 5.88−5.76 (H3) ↔
δ 2.90−2.77 (H4), 2.66−2.55 (H4′); δ 5.88−5.76 (H2) ↔ δ 2.90−2.77
−30 °C in the glovebox. 1H NMR (400 MHz, C6D6): δ 3.98 (d, J1−2
4.9 Hz, 1H, H1), 3.84 (dd, J2−3 = 7.1 Hz, J2−1 = 4.8 Hz, 1H, H2), 2.65
(dd, J8eq−8ax = 12.8 Hz, J8eq−7eq = 2.4 Hz, 1H, H8eq), 2.14 (ddt, J7eq−7ax
=
=
13.7 Hz, J7eq−6ax = 4.5 Hz, J7eq−6eq = J7eq−8eq = 2.0 Hz, 1H, H7eq), 1.97
(ddd, J3−2 = 7.6 Hz, J3−4endo = 5.7 Hz, J3−4exo = 2.6 Hz, 1H, H3), 1.72
(dtd, J6eq−6ax = 13.7 Hz, J6eq−7ax = J6eq−7eq = 7.4 Hz, J6eq−5 = 0.8 Hz,
1H), 1.61 (dt, J8ax−8eq = 12.9 Hz, J8ax−7ax = J8ax−7eq = 1.0 Hz, 1H, H8ax),
(H1); δ 5.62 (H5) ↔ δ 5.28 (H6), 2.90−2.77 (H4), 2.66−2.55 (H4′
+
H7); δ 5.28 (H6) ↔ δ 2.66−2.55 (H7); δ 2.90−2.77 (H1) ↔ δ 2.66−
2.55 (H7); δ 2.90−2.77 (H4) ↔ δ 2.66−2.55 (H4′); δ 2.66−2.55 (H7)
↔ δ 1.37−1.21 (H8ax); δ 2.35 (H10eq) ↔ δ 1.87−1.69 (H8eq + H9eq
+
1.54 (s, 15H, C5Me5), 1.13 (tdd, J6ax−6eq = J6ax−5/7ax = 13.6 Hz, J6ax−5/7ax
=
H10ax), 1.37−1.21 (H9ax); δ 1.87−1.69 (H8eq + H9eq) ↔ δ 1.37−1.69
(H8ax + H9ax). 13C{1H} NMR (100 MHz, CDCl3): δ 173.1, 171.3,
135.5, 132.2, 130.0, 126.8, 59.6, 52.7, 52.2, 45.9, 36.6, 34.1, 33.6, 26.7,
22.3. Electrospray MS: m/z calculated for C15H20O4Na (M+ + Na)
287.12538, found 287.12541 (100%).
12.6 Hz, J6ax−7eq = 4.8 Hz, 1H, H6ax), 1.02−0.95 (m, 3H, H4endo, H4exo
,
H7ax), 0.92 (s, 3H, Me), 0.90 (d, JMe‑1 = 1.0 Hz, 3H, Me), 0.57 (m, 1H,
H5). 1H−1H GCOSY (400 MHz, C6D6): δ 3.98 (H1) ↔ δ 3.84 (H2),
0.90 (Me); δ 3.84 (H1) ↔ δ 1.97 (H3), 1.02−0.95 (H4endo); δ 2.65
(H8eq) ↔ δ 2.14 (H7eq), 1.61 (H8ax); δ 2.14 (H7eq) ↔ δ 1.72 (H6eq),
[5.4.0]-Bicycloundeca-8,10-dien-3-one (49). Bicyclic cobalt
complex 42 (75 mg, 0.21 mmol) was dissolved in THF (20 mL) in
the glovebox and placed in a glass reaction bomb. To this was added
allyl bromide (20 μL, 0.23 mmol), and the bomb was sealed and
irradiated with UV light in a Rayonet carousel for 16 h, resulting in a
green solution. The solvent was removed in vacuo and the product
purified by silica gel chromatography using 19:1 hexanes/diethyl ether,
with the product dissolved in a minimal amount of CH2Cl2 for loading
onto the column, providing 34 mg (100%) of bicyclic organic product
1.13 (H6ax); δ 1.97 (H3) ↔ δ 1.02−0.95 (H4endo, H4exo); δ 1.72 (H6eq
)
↔ δ 1.13 (H6ax), 1.02−0.95 (H7ax); δ 1.13 (H6ax) ↔ δ 1.02−0.95 (H7ax),
0.57 (H5); δ 1.02−0.95 (H4endo, H4exo) ↔ δ 0.57 (H5). 13C{1H} NMR
(100 MHz, C6D6): δ 208.9, 90.0, 84.5, 80.8, 66.0, 54.2, 51.7, 43.2, 41.2,
39.8, 30.9, 29.9, 23.8, 18.1, 9.9. Electron impact MS: m/z calculated for
C23H33OCo (M+) 384.18634, found 384.18677 (99%).
trans-Dimethyl 2,3,3a,4-Tetrahydroazulene-1,1(8aH)-dicar-
boxylate (47). Bicyclic cobalt complex 38 (15 mg, 0.034 mmol)
was dissolved in THF (5 mL mL) in the glovebox and placed in a glass
reaction bomb. To this, allyl bromide (2.9 μL, 0.034 mmol) was added,
the bomb sealed and irradiated with UV light in a Rayonet carousel for
16 h resulting in a red solution. The solvent was removed in vacuo and
the product purified by silica gel chromatography using 19:1 hexanes/
diethyl ether, with the product dissolved in a minimal amount of
CH2Cl2 for loading onto the column, providing 7.8 mg (92%) of bi-
cyclic organic product 47 as a pale yellow oil. IR (CH2Cl2 cast, cm−1):
3016 (s), 3954 (s), 2870 (s), 1731 (s), 1610 (w), 1435 (s), 1379 (w),
1435 (s), 1329 (w), 1269 (s), 1225 (s), 1172 (s), 1079 (s), 1017 (s),
989 (w). 1H NMR (400 MHz, CDCl3): δ 5.82 (m, 1H, H2), 5.76−5.70
(m, 3H, H3, H4, H5), 3.75 (s, 3H, −OMe), 3.72 (s, 3H, −OMe), 3.03
(dq, J1−7 = 10.4 Hz, J1−2 = J1−3 = J1−9 = 1.6 Hz, 1H, H1), 2.52 (dddd,
1
49 as a clear oil. H NMR (400 MHz, CDCl3): δ 5.89 (m, 1H, H5),
5.81 (m, 2H, H4, H3), 5.37 (m, 1H, H2), 2.53 (m, 1H, H1), 2.45 (ddd,
J10eq−10ax = 14.4 Hz, J10eq−1 = 4.2 Hz, J10eq−9eq = 1.8 Hz, 1H, H10eq),
2.37−2.34 (m, 2H, H9, H6), 2.32−2.26 (m, 2H, H10ax, H6′), 2.04 (m,
1
1H, H8), 1.98 (m, 1H, H7), 1.59−1.48 (m, 2H, H8′, H9′). H−1H
COSY (400 MHz, CDCl3): δ 5.89 (H5) ↔ δ 5.81 (H4), 2.37−2.34
(H6); δ 5.81 (H4, H3) ↔ δ 5.37 (H2), 2.53 (H1), 2.37−2.34 (H6); δ
5.37 (H2) ↔ δ 2.53 (H1); δ 2.53 (H1) ↔ δ 2.45 (H10eq), 2.32−2.26
(H10ax), 1.98 (H7); δ 2.45 (H10eq) ↔ δ 2.32−2.26 (H10ax); δ 2.37−2.34
(H9) ↔ δ 1.59−1.48 (H9′), 2.04 (H8), 1.59−1.48 (H8′); δ 2.04 (H8)
↔ δ 1.59−1.48 (H8′, H9′), 1.98 (H7); δ 1.98 (H7) ↔ δ 1.59−1.48
(H8′, H9′). 13C{1H} NMR (100 MHz, CDCl3): δ 211.1, 135.3, 132.4,
125.1, 124.6, 47.4, 46.8, 40.2, 40.1, 36.1, 33.9. Electrospray MS: m/z
calculated for C11H14O (M+): 162.10446, found 162.10431 (11%).
trans-9,9a-Dimethyl-3,4,4a,5-tetrahydro-1H-benzo[7]-
annulen-2(9aH)-one (50). Bicyclic cobalt complex 46 (5 mg,
0.01 mmol) was dissolved in THF (10 mL) in the glovebox and
placed in a glass reaction bomb. To this was added allyl bromide
(1.2 μL, 0.01 mmol), and the bomb was sealed and irradiated with UV
light in a Rayonet carousel for 16 h, resulting in a green solution. The
solvent was removed in vacuo and the product purified by silica gel
chromatography using 19:1 hexanes/diethyl ether, with the product
dissolved in a minimal amount of CH2Cl2 for loading onto the column,
providing 2.5 mg (100%) of bicyclic organic product 50 as a pale
yellow oil. IR (neat, cm−1): 3023 (w), 2965 (s), 2928 (s), 1716 (s),
1611 (w), 1458 (m), 1432 (m), 1375 (w), 1354 (w), 1318 (w), 1294
(w), 1243 (w), 1218 (w), 1178 (w), 1124 (w), 1104 (w), 1000 (w).
1H NMR (400 MHz, CDCl3): δ 5.77 (m, 1H, H3), 5.67 (dd, 1H,
J
6−6′ = 17.8 Hz, J6‑7 = 6.6 Hz, J6−5 = 3.2 Hz, J6−4 =1.4 Hz, 1H, H6), 2.41
(ddd, J9−9′ =13.7 Hz, J9−8 = 8.6 Hz, J9−8′ = 6.9 Hz, 1H, H9), 2.38 (m,
1H, H7), 2.30−2.10 (m, 3H, H6′, H8, H9′), 1.34 (dddd, J8′‑8 = 12.8 Hz,
1
J8′‑7 = 9.4 Hz, J8′‑9′ = 8.4 Hz, J8′‑9 = 6.0 Hz, 1H, H8′). H−1H COSY
(400 MHz, CDCl3): δ 5.82 (H2) ↔ δ 5.76−5.70 (H3), 3.03 (H1); δ
5.76−5.70 (H3) ↔ δ 3.03 (H1); δ 5.76−5.70 (H4, H5) ↔ δ 2.52 (H6),
2.30−2.10 (H6′); δ 3.03 (H1) ↔ δ 2.38 (H7); δ 2.52 (H6) ↔ δ 2.38
(H7), 2.30−2.10 (H6′); δ 2.41 (H9) ↔ δ 2.30−2.10 (H8, H9′); δ 2.38
(H7) ↔ δ 2.30−2.10 (H8), 1.34 (H8′); δ 2.30−2.10 (H8, H9′) ↔ δ
1.34 (H8′). 13C{1H} NMR (100 MHz, CDCl3): δ 172.8, 172.3, 132.2,
130.9, 125.0, 124.4, 64.1, 54.3, 52.8, 52.5, 41.2, 37.7, 34.1, 31.7.
Electron impact MS: m/z calculated for C14H18O4 (M+) 250.12051,
found 250.12044 (23%).
[5.4.0]-2,2-Bis(methylcarboxyl)bicycloundeca-7,10-diene
(48). Bicyclic cobalt complex 39 (70 mg, 0.15 mmol) was dissolved in
THF (20 mL) in the glovebox and placed in a glass reaction bomb. To
this was added allyl bromide (15 μL, 0.17 mmol), and the bomb was
sealed and irradiated with UV light in a Rayonet carousel for 16 h,
resulting in a green solution. The solvent was removed in vacuo and
the product purified by silica gel chromatography using 19:1 hexanes/
diethyl ether, with the product dissolved in a minimal amount of
CH2Cl2 for loading onto the column, providing 35 mg (85%) of
bicyclic organic product 48 as a clear oil. If reactions were run at
higher concentration, a red solution was obtained. Again, concen-
tration in vacuo followed by careful chromatography would allow
J2−3 = 7.6 Hz, J2−1 = 2.6 Hz, H2), 5.61 (m, 1H, H1), 2.53 (dd, J8eq−8ax
=
13.3 Hz, J8eq−7eq = 2.1 Hz, 1H, H8eq), 2.38 (d, J8ax−8eq = 13.3 Hz, 1H,
H8ax), 2.43−2.31 (m, 3H, H4, H7ax, H7eq), 2.24 (tdd, J5−6ax = J5−4 = 12.5
Hz, J5−6eq = 4.0 Hz, J5−4′ = 1.7 Hz, 1H, H5), 2.12 (ddd, J4′‑4 = 17.8 Hz,
J4′‑3 = 7.5 Hz, J4′‑5 = 1.5 Hz, 1H, H4′), 1.97 (dddd, J6eq−6ax = 13.8 Hz,
J6eq−7eq = 6.6 Hz, J6eq−5 = 4.0 Hz, J6eq−7ax = 2.6 Hz, 1H, H7eq), 1.83 (s,
3H, Me), 1.77 (qd, J6ax−6eq = J6ax−5 = J6ax−7ax = 13.5 Hz, J6ax−7eq = 5.5
Hz, 1H, H6ax), 1.05 (s, 3H, Me). 1H−1H GCOSY (400 MHz, CDCl3):
δ 5.77 (H3) ↔ δ 5.67 (H2), 2.12 (H4′); δ 5.67 (H2) ↔ δ 5.61 (H1); δ
5.61 (H1) ↔ δ 1.83 (Me); δ 2.53 (H8eq) ↔ δ 2.38 (H8ax), 2.43−2.31
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Organometallics
Article
(H7eq); δ 2.43−2.31 (H4) ↔ δ 2.24 (H5), 2.12 (H4′); δ 2.43−2.31
(H7ax/7eq) ↔ δ 1.97 (H6eq), 1.77 (H6ax); δ 2.24 (H5) ↔ δ 2.12 (H4′),
1.97 (H6eq), 1.77 (H6ax); δ 1.97 (H6eq) ↔ δ 1.77 (H6ax). 13C{1H}
NMR (100 MHz, CDCl3): δ 212.1, 146.1, 131.8, 124.8, 122.1, 52.7,
47.4, 42.3, 40.9, 34.4, 31.1, 23.2, 20.1. Electron impact MS: m/z
calculated for C13H18O (M+) 190.13577, found 190.13592 (93%).
(d) Kreiter, C. G.; Fiedler, C.; Frank, W.; Reiss, G. J. Chem. Ber. 1995,
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Ernst, R. D. J. Organomet. Chem. 2006, 691, 5211−5217.
(5) Witherell, R. D.; Ylijoki, K. E. O.; Stryker, J. M. J. Am. Chem. Soc.
2008, 130, 2176−2177.
ASSOCIATED CONTENT
* Supporting Information
■
S
Figures, tables, and CIF files giving crystallographic data,
ORTEP diagrams, crystal data collection and refinement of
parameters, atomic coordinates, bond distances and angles, and
isotropic displacement parameters for complexes 2f, 3g, 8a, 24,
30−32, 34, 35, and 42. The Supporting Information is available
free of charge on the ACS Publications website at DOI:
10.1021/acs.organomet.5b00346.
(6) Ylijoki, K. E. O.; Witherell, R. D.; Kirk, A. D.; Bocklein, S.;
̈
Lofstrand, V. A.; McDonald, R.; Ferguson, M. J.; Stryker, J. M.
Organometallics 2009, 28, 6807−6822.
AUTHOR INFORMATION
Corresponding Authors
*E-mail for K.E.O.Y.: kai.ylijoki@smu.ca.
*E-mail for J.M.S.: jeff.stryker@ualberta.ca.
■
(7) An earlier assertion that protonation of Cp*Co(η4-cyclo-
heptatriene) leads to the nonconjugated Cp*Co(η2,η3-cyclohepta-
diene) cation is not supported by spectroscopic evidence: Lewis, J.;
Parkins, A. W. J. Chem. Soc. A 1969, 953−957. The product was later
shown to be the expected η5-cycloheptadienyl cation: Salzer, A.; Bigler,
P. Inorg. Chim. Acta 1981, 48, 199−203.
Present Address
§Clariant Produkte (Deutschland) GmbH, Waldheimer Str. 13,
(8) (a) Schwiebert, K. E.; Stryker, J. M. J. Am. Chem. Soc. 1995, 117,
8275−8276. (b) Etkin, N.; Dzwiniel, T. L.; Schwiebert, K. E.; Stryker,
J. M. J. Am. Chem. Soc. 1998, 120, 9702−9703.
83052 Bruckmuhl, Germany.
̈
Author Contributions
All authors have given approval to the final version of the
manuscript.
(9) Dzwiniel, T. L.; Etkin, N.; Stryker, J. M. J. Am. Chem. Soc. 1999,
121, 10640−10641.
(10) Dzwiniel, T. L.; Stryker, J. M. J. Am. Chem. Soc. 2004, 126,
9184−9185.
Notes
The authors declare no competing financial interest.
(11) (a) Bennett, M. A.; Nicholls, J. C.; Rahman, A. K. F.; Redhouse,
A. D.; Spencer, J. L.; Willis, A. C. J. Chem. Soc., Chem. Commun. 1989,
1328−1330. (b) Nicholls, J. C.; Spencer, J. L. Organometallics 1994,
13, 1781−1787. (c) Cracknell, R. B.; Nicholls, J. C.; Spencer, J. L.
Organometallics 1996, 15, 446−448.
ACKNOWLEDGMENTS
■
Financial support from the Natural Sciences and Engineering
Research Council of Canada, the Province of Alberta (Q.E. II
Graduate Scholarships to K.E.O.Y. and A.D.K.), and the
University of Alberta is gratefully acknowledged.
(12) Ylijoki, K. E. O.; Budzelaar, P. H. M.; Stryker, J. M. Chem.Eur.
J. 2012, 18, 9894−9900.
(13) Crystallographic information files (CIF) and full crystallographic
structure reports are provided as Supporting Information.
ABBRVIATIONS
Cp*, (C5Me5); Cp, (C5H5); DFT, density functional theory
■
́
(14) Sanchez-Castro, M. E.; Ramirez-Monroy, A.; Paz-Sandoval, M.
A. Organometallics 2005, 24, 2875−2888.
(15) The 1-methyl complex 6a has been tentatively shown to react
with ethoxyacetylene and TMS-acetylene. The reaction with
ethoxyacetylene is rapid, occurring in 30 min at room temperature,
which agrees with the observation that electron-rich alkynes are more
reactive in the Cp* series. The TMS-acetylene reaction required mild
heating for 3 days. 1H NMR spectroscopy of the crude products
indicated the reactions were reasonably clean, resulting in 1:1 mixtures
of regiosiomeric η2,η3-cycloheptadienyl complexes.
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