C-C and C-N Couplings in Reactions of the Benzylidyne-Bridged Complex [Mo2Cp2(μ-CPh)(μ-PCy2)(CO)2] with Small Unsaturated Organics

Article abstract of DOI:10.1021/acs.organomet.6b00552

The ability of the title compound to promote C-C coupling processes has been analyzed by examining its reactions with diazoalkanes, alkynes, and other unsaturated organic molecules. The title compound reacted with N₂CPh₂ at room temp

Full text of DOI:10.1021/acs.organomet.6b00552

Article
pubs.acs.org/Organometallics
C−C and C−N Couplings in Reactions of the Benzylidyne-Bridged
Complex [Mo2Cp2(μ-CPh)(μ-PCy2)(CO)2] with Small Unsaturated
Organics
M. Esther García, Daniel García-Vivo, Sonia Menendez, and Miguel A. Ruiz*
́
́
́ ́
Departamento de Química Organica e Inorganica/IUQOEM, Universidad de Oviedo, E-33071 Oviedo, Spain
S
* Supporting Information
ABSTRACT: The ability of the title compound to promote C−C coupling
processes has been analyzed by examining its reactions with diazoalkanes,
alkynes, and other unsaturated organic molecules. The title compound reacted
with N2CPh2 at room temperature to give a mixture of ketenyl complex
[Mo2Cp2{μ-κ1:η2-C(Ph)CO}(μ-PCy2)(CO)(κ1-N2CPh2)] and carbyne com-
plex [Mo2Cp2(μ-CPh)(μ-PCy2)(CO)(κ1-N2CPh2)], products which can be
converted into each other by addition/removal of CO, respectively. In contrast,
denitrogenation took place rapidly in analogous reactions with diazomethane
and benzylazide at room temperature, to yield, respectively, the corresponding
alkenyl [Mo2Cp2{μ-κ1:η2-C(Ph)CH2}(μ-PCy2)(CO)2] and iminoacyl
[Mo2Cp2{μ-C(Ph)NCH2Ph}(μ-PCy2)(CO)2] derivatives, following from
selective C−C and C−N couplings. The title compound reacted at 333 K
with methyl propiolate to give the corresponding propenylylidene derivative
[Mo2Cp2{μ-κ2:η3-CPhCHC(CO2Me)}(μ-PCy2)(CO)2], as a result of selective coupling of the carbyne ligand to the terminal
carbon of the alkyne. A related complex could be obtained when using the internal alkyne dimethyl acetylenedicarboxylate.
Some time ago we reported the preparation of 32-electron
benzylidyne complex [Mo2Cp2(μ-CPh)(μ-PCy2)(CO)2] (1),
an unsaturated compound readily reacting with CO to give
ketenyl-bridged derivative [Mo2Cp2{μ-C(Ph)CO}(μ-PCy2)-
(CO)2] (2), a molecule still retaining substantial unsaturation
at the dimetal site (Scheme 1).4a,8 This result was somewhat
unexpected by recalling that the related methoxycarbyne-
bridged complex would react under analogous conditions to
just give the corresponding electron-precise tricarbonyl
derivative, with this being accompanied by a trans to cis
INTRODUCTION
■
Carbyne complexes constitute a vast family of organometallic
molecules with a rich chemistry derived from the multiple
character of the metal−carbyne bond, of the highest order for
terminal ligands.1 Multiplicity in the M−C bond is significantly
reduced in carbyne-bridged binuclear complexes, hence the
corresponding reactivity, but the latter can be increased in the
presence of metal−metal multiple bonds, thus promoting fast
coordination of external molecules and allowing for possible
cooperative effects between M−M and M−C multiple bonds.2
For instance, we have shown previously that 30-electron
complex cations of the type [Mo2Cp2(μ-CX)(μ-COR)(μ-
PCy2)]+ (X = OMe and Ph; R = H and Me) with metal−
metal triple bonds add readily simple ligands such as CO and
isocyanides, thus promoting C−C coupling processes between
carbyne ligands which can be reversed,3,4 and a similarly
reversible P−C coupling between phosphanyl and benzylidyne
ligands can be induced at the triply bonded thiolate-bridged
complex [Mo2Cp2(μ-CPh)(μ-PCy2)(μ-SPh)]+ upon carbon-
ylation to give the corresponding phosphinocarbene derivative.5
Nucleophilic attack of simple ligands on bridging carbyne
groups to give carbene or related derivatives, however, can also
occur at electron-precise complexes provided they are electro-
philic enough, a circumstance particularly well met for cationic
complexes.6 For instance, methylidyne-bridged diiron cation
[Fe2Cp2(μ-CH)(μ-CO)(CO)2]+ has been shown to react
under mild conditions with CO and CNtBu to give the
corresponding ketenyl- and iminoketenyl-bridged derivatives.7
Scheme 1
Received: July 11, 2016
Published: October 13, 2016
© 2016 American Chemical Society
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rearrangement of the Mo2Cp2 platform.9 This difference
pointed to some particular preference of complex 1 for C−C
coupling processes involving the carbyne ligand, a sort of
reaction of general interest in the context of Fischer−Tropsch
chemistry, which involves C−C couplings between different
hydrogenation products of carbon monoxide, notably methyne
and methylene ligands.10 We here analyze the ability of 1 to
promote this sort of C−C coupling by exploring its reactions
with diazoalkanes, alkynes, and some other small unsaturated
organic molecules. A preliminary account of some of these
reactions has appeared.11
The formation of 3 gives experimental support to our
previous hypothesis that carbonylation of 1 to yield ketenyl
complex 2 would likely imply initial coordination of CO to the
unsaturated dimetal center of 1 followed by reorganization,
rather than direct attack of CO to the electron-rich carbyne
ligand.8 In line with this hypothesis, 31P NMR monitoring of
the carbonylation reaction of 4 revealed the transient formation
of two new species A and B (identified by 31P NMR resonances
at 201.5 and 197.4 ppm) which were also detected as
intermediate species in the reaction of 1 with N2CPh2. These
transient species seem to be the actual precursors of ketenyl
complex 3 and presumably are two isomers of the electron-
precise species [Mo2Cp2(μ-CPh)(μ-PCy2)(CO)2(κ1-N2CPh2)]
that would follow either from coordination of a diazoalkane
molecule to complex 1 or from coordination of a CO molecule
to complex 4, thus being structurally related to the tricarbonyl
complex [Mo2Cp2(μ-COMe)(μ-PCy2)(CO)3] depicted in
Scheme 1.
The presence of a ketenyl ligand in 3 suggests that this
complex could possibly also be obtained through reaction of
diphenyldiazomethane with ketenyl complex 2. Indeed, such
reaction takes place rapidly at room temperature, but the
product is an isomer of the sought complex, now with the
terminal carbonyl and diazoalkane ligands in a cisoid arrange-
ment (cis-3, Scheme 2). This complex can be decarbonylated
under the same conditions used for its transoid isomer (toluene
solution, 353 K, 30 min), which now gives the corresponding
carbyne derivative cis-4, along with a small amount of transoid
isomer 4 (ratio ca. 5/1), thus indicating a good retention of the
stereochemistry at the Mo2Cp2 platform. The formation of cis-
4, however, is now an irreversible process, since carbonylation
of the latter does not regenerate the cisoid isomer but rather
the transoid one, 3 (Scheme 2).
RESULTS AND DISCUSSION
■
Reactions with Diphenyldiazomethane. Compound 1
reacts with N2CPh2 at room temperature, but only at very high
concentrations of reagents, to give a mixture of two products
having in each case a metal-bound diazoalkane molecule:
ketenyl complex [Mo2Cp2{μ-κ1:η2-C(Ph)CO}(μ-PCy2)(CO)-
(κ1-N2CPh2)] (3) and carbyne complex [Mo2Cp2(μ-CPh)(μ-
PCy2)(CO)(κ1-N2CPh2)] (4). Separate experiments revealed
that these products are related by carbonylation/decarbon-
ylation processes, therefore allowing for their selective
preparation (Scheme 2). Thus, the above mixture can be
Scheme 2
Structural Characterization of Ketenyl Complexes 3.
The structure of transoid isomer 3 was determined by an X-ray
study during our preliminary analysis of the chemistry of 1
(Figure 1)11 and will be only briefly discussed here. The
terminal diazoalkane ligand displays an imido-like coordination
Figure 1. ORTEP drawing (30% probability) of compound 3, with H
atoms, cyclohexyl, and phenyl rings (except the C1 atoms) omitted for
clarity.11 Selected bond lengths (Å) and angles (deg): Mo1−Mo2 =
2.8935(9), Mo1−P1 = 2.364(2), Mo1−C1 = 1.932(8), Mo1−C2 =
2.163(7), Mo1−C3 = 2.203(7), Mo2−P1 = 2.432(2), Mo2−C3 =
2.148(7), Mo2−N1 = 1.748(5), N1−N2 = 1.338(7), N2−C10 =
1.306(8), C3−C2 = 1.398(9), C2−O2 = 1.215(8); Mo2−Mo1−C1 =
96.4(2), Mo1−Mo2−N1 = 103.6(2), Mo2−N1−N2 = 174.6(5), N1−
N2−C10 = 120.0(6), C3−C2−O2 = 142.3(7), Mo1−C2−O2 =
144.2(5).
transformed into pure 3 upon reaction with CO (ca. 3 atm) in
dichloromethane solution at room temperature. In contrast,
heating a toluene solution of this mixture at 353 K for 30 min
yields pure compound 4 (see the Experimental Section). We
note that no denitrogenation of the diazoalkane molecule is
observed in the above reactions, a circumstance also observed
in reactions of this reagent with triply bonded
[Mo2Cp2(CO)4]12 and more recently in reactions with 30-
electron ditungsten hydride [W2Cp2H(μ-PCy2)(CO)2].13
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Table 1. Selected IR and NMR Data for New Compounds
a
b
b
compound
ν(CO)
δ(P)
δ(μ-C)
c
[Mo2Cp2(μ-CPh)(μ-PCy2)(CO)2] (1)
1905 (w, sh), 1880 (vs)
117.6
132.6
216.4
202.7
188.7
185.1
143.6
155.5
140.3
154.7
135.7
428.4 [5]
15.8 [1]
134.4
c
[Mo2Cp2{μ-C(Ph)CO}(μ-PCy2)(CO)2] (2)
1993 (s), 1895 (s), 1838 (vs)
1864 (s)
[Mo2Cp2{μ-κ1:η2-C(Ph)CO}(μ-PCy2)(CO)(κ1-N2CPh2)] (3)
cis-[Mo2Cp2{μ-κ1:η2-C(Ph)CO}(μ-PCy2)(CO)(κ1-N2CPh2)] (cis-3)
[Mo2Cp2(μ-CPh)(μ-PCy2)(CO)(κ1-N2CPh2)] (4)
1877 (s)
132.7
1872 (s)
373.5 [6]
cis-[Mo2Cp2(μ-CPh)(μ-PCy2)(CO)(κ1-N2CPh2)] (cis-4)
[Mo2Cp2{μ-κ1:η2-C(Ph)CH2}(μ-PCy2)(CO)2] (5)
1895 (s)
1884 (s), 1790 (m)
1885 (w, sh), 1859 (vs)
182.0
d
d
[Mo2Cp2{μ-C(Ph)NCH2Ph}(μ-PCy2)(CO)2] (6)
189.9 [23]
e
e
[Mo2Cp2{μ-κ2:η3-CPhCHC(CO2Me)}(μ-PCy2)(CO)2] (7a)
[Mo2Cp2{μ-κ2:η3-CPhC(CO2Me)C(CO2Me)}(μ-PCy2)(CO)2] (7b)
cis-[Mo2Cp2{μ-κ2:η3-CPhC(CO2Me)C(CO2Me)}(μ-PCy2)(CO)2] (cis-7b)
1916 (s), 1886 (vs), 1676 (w), 1658 (w)
137.7, 78.4 [28]
101.0, 80.0 [24]
99.5, 63.7 [30]
e
1926 (m, sh), 1910 (vs), 1676 (m)
e
1964 (vs), 1909 (w, sh), 1670 (w)
a
b
Recorded in dichloromethane solution, ν in cm−1. Recorded in CD2Cl2 solutions at 290 K and 300.13 (1H), 121.50 (31P), or 75.47 (13C) MHz, δ
in ppm relative to internal TMS (1H, 13C) or external 85% aqueous H3PO4 (31P); coupling constants to 31P are shown in square brackets and are
given in Hz. Data taken from ref 8. Recorded at 253 K. Stretch of CO2Me groups.
c
d
e
mode,14 with almost triple Mo−N (1.748(5) Å) and single N−
N (1.338(7) Å) bonds, and therefore acts as a four-electron
donor to the dimetal center, as previously found in related
complexes [W2Cp2(μ-PPh2)2(CO)(κ1-N2CPh2)],15a
[Mo2Cp2(CO)3(CPh2)(κ1-N2CPh2)],15b and [W2Cp2H(μ-
PCy2)(CO)2{κ1-N2CH(SiMe3)}].13 The superior donor ability
of the diazoalkane ligand (compared to CO) is balanced by an
alkenyl-like asymmetric coordination (μ-κ1:η2 mode) of the
three-electron donor ketenyl ligand, η2-bound to the carbonyl-
bearing Mo atom, and by a stronger coordination of the PCy2
ligand to that atom. Overall, the molecule formally is electron-
precise, and this is in agreement with the relatively large
intermetallic length of ca. 2.90 Å. We finally note that the
asymmetric coordination mode of the ketenyl ligand found in 3
has been previously characterized in a few, usually hetero-
metallic substrates,16 the only homometallic precedent being
ditungsten complex [W2(μ-Br)Br2{μ-κ1:η2-C(4-Me-C6H4)-
CO}(CO){μ-F2PN(Me)PF2}2].17
Spectroscopic data for 3 are consistent with retention in
solution of the structure found in the crystal. In particular, we
note that its 31P NMR resonance is considerably more
deshielded than that of the 32-electron precursor 1 (Table 1)
and has a chemical shift rather approaching the values found for
related electron-precise complexes (cf. 218.8 ppm for
[Mo2Cp2(μ-H)(μ-PCy2)(CO)4]).18 This requires the retention
of the 3-electron donor μ-κ1:η2 coordination of the ketenyl
ligand in solution, rather than adopting the more symmetrical
μ-κ1:κ1 mode found in complex 2, which is consistent with the
large difference in the 13C chemical shifts of the corresponding
bridgehead carbon atoms of these two compounds (134.4 vs
15.8 ppm). Spectroscopic data for cisoid isomer cis-3 are similar
to those of 3 as expected. Interestingly, its C−O stretching
frequency is a bit higher, as usually found when comparing
related pairs of cis and trans isomers of oxo carbonyl complexes
[Mo2Cp2(μ-CPh)(μ-PCy2)(O)(CO)]19 and [Mo2Cp2(μ-
PPh2)2(O)(CO)],20 which are isoelectronic with our diazo-
alkane complexes. The conformation assumed for this cisoid
isomer is consistent with the observation of a positive NOE
enhancement between the hydrogen atoms of the Cp rings and
those of the phenyl ring of the carbyne ligand.
CPh)(μ-PCy2)(O)(CO)] structurally characterized recently by
us.19 Indeed, spectroscopic data for 4 and cis-4 are comparable
to those of the mentioned oxo complexes as concerning their
considerably deshielded 31P (ca. 190 ppm) and 13C(carbyne)
NMR resonances; as expected, the cis isomer displays a C−O
stretching frequency significantly higher than that of the trans
isomer 4 (Table 1). The structural data of the oxo complexes
mentioned above indicate that in order to balance the much
stronger donor ability of the oxo ligand (compared to CO)
both the carbyne and the bridging PCy2 groups bind more
tightly the carbonyl-bearing Mo atom, and the same structural
effect is assumed to occur for our diazoalkane complexes, which
are thus depicted in Scheme 2 with a very asymmetric
coordination of the bridging ligands.
Reaction of 1 with Diazomethane. In contrast to the
reaction with diphenyldiazomethane discussed above, deni-
trogenation takes place rapidly in the reaction of 1 with
diazomethane at room temperature. This incorporates a
methylene group to the dimetal center of 1, eventually coupled
with the carbyne ligand to yield the 32-electron alkenyl-bridged
derivative [Mo2Cp2{μ-κ1:η2-C(Ph)CH2}(μ-PCy2)(CO)2] (5)
(Chart 1). This sort of reaction is well-documented in the
Chart 1
chemistry of heterometallic carbyne-bridged complexes1b and
has been also observed previously for cationic methoxycarbyne
complex [W2Cp2(μ-COMe)(CO)2(μ-Ph2PCH2PPh2)]+, a mol-
ecule isoelectronic to 1.21
We have previously reported the preparation of complexes
very similar to 5 through the reaction of the unsaturated
hydrides [M2Cp2(μ-H)(μ-PCy2)(CO)2] with HCC(p-tol) (M
= Mo and W; p-tol =4-C6H4Me).22 Spectroscopic data for 5
(Table 1 and Experimental Section) are indeed very similar to
those of the mentioned p-tol-substituted compounds and will
not be discussed in detail. We note that these complexes are
thermally unstable and evolve at room temperature to yield the
Solution Structure of Carbyne Complexes 4. Com-
pound 4 and its cis isomer are assumed to display terminal,
imido-like diazoalkane ligands, as found for 3. This renders
electron-precise molecules which are isoelectronic with
carbyne-bridged oxo complexes trans- and cis-[Mo2Cp2(μ-
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corresponding β-substituted alkenyl isomers, a transformation
also observed for 5 but not investigated in detail.
ca. 30 Hz, with the latter feature being related to the acute value
of the P−M−C angle in this arrangement for the mentioned
complexes (N atom close to the M2P plane). Only in the case
of complex [W2Cp2(μ-κ1:κ1-HCNXyl)(μ-PCy2)(CO)2] have
we found that the preferred coordination of the C,N-donor
ligand was the 3-electron donor μ-κ1:κ1 mode (B in Chart 2),
which was attributed to steric effects,26 and the formimidoyl
carbon atom in this complex expectedly gives rise to a quite
deshielded 13C NMR resonance (215.0 ppm) with negligible
P−C coupling (the computed P−W−C angle in this arrange-
ment is ca. 125°). Thus, the carbon atom of the formimidoyl
ligand in 6 seems to have a chemical shift not far from that
expected for mode B but rather a P−C coupling indicative of a
P−Mo−C angle substantially different. In search for possible
structural alternatives we noticed that an analysis of the
crystallographic databases revealed that in the case of
formimidoyl-bridged complexes there were a few examples
displaying a third possible coordination geometry for this sort
of bridging ligand, the planar μ-κ1:η2 mode (C in Chart 2),27
this implying a less obvious formal contribution to the dimetal
center somewhere between 3 and 5 electrons depending on the
degree of π(N to M) bonding contribution to the M−N
interaction. Still nonplanar, μ-κ1:η2 coordination modes can be
also conceived for these sort of C,N-donor ligands (D and E in
Chart 2), although no examples of them seem to have been
identified crystallographically so far.
The NMR spectroscopic properties of the iminoacyl carbon
atom in 6 (high chemical shift and high P−C coupling) might
be consistent with a nonplanar coordination of type E for the
iminoacyl ligand in this compound. To test such hypothesis, we
resorted to density functional theory (DFT) calculations in
search of likely energy minima of this compound (see
Experimental Section and the Supporting Information for
details). We explored for 6 possible geometries for all
coordination modes A−E, but no energy minima with
iminoacyl coordination of types C and E were found. The
most stable isomer was found to be the one of type B, followed
by two isomers of type A (6A1 and 6A2 in Figure 2).
Incidentally, we recall here that the same relative ordering was
computed for formimidoyl complex [W2Cp2(μ-κ1:κ1-
HCNXyl)(μ-PCy2)(CO)2].26 We also note that two isomers
of type D were found, but these were too energetic (some 80
kJ/mol above 6B) to be considered as likely structures for
compound 6. Interestingly, the computed 13C NMR parameters
for the most stable isomers, 6B and 6A1 (see the Supporting
Information), reproduced reasonably well the experimental
values already discussed that were measured for compounds
actually displaying such structures,25,26 thus giving credibility to
our hypothesis that the actual structure of 6 in solution does
not correspond to any of the types A−D. We still consider a
structure of type E, which can be viewed as intermediate
between structures 6A1 and 6B, as the more likely structure for
compound 6 in solution. Perhaps our failure to find such a
minimum in the corresponding potential energy surface is
related to the low thermal stability of this compound, possibly a
kinetic product which decomposes rapidly to products different
from its more stable iminoacyl isomer 6B.
Reaction of 1 with Benzylazide. As found in the reactions
with diphenyldiazomethane, reaction of 1 with benzylazide
occurs at room temperature but only at high concentration of
reagents and proceeds with denitrogenation along with carbyne
to nitrene coupling, to eventually give iminoacyl-bridged
derivative [Mo2Cp2{μ-C(Ph)NCH2Ph}(μ-PCy2)(CO)2] (6)
in good yield (Chart 1). Related heterocumulenes such as
tBuNCO and (p-tol)NCS failed to react with 1 under the same
conditions. Compound 6 was thermally unstable and
decomposed slowly at room temperature to give a mixture of
uncharacterized species. Unfortunately, all attempts to grow
single crystals of this product were unsuccessful, and the precise
definition of the coordination mode of the iminoacyl ligand in 6
remains somewhat uncertain even after consideration of the
corresponding spectroscopic data and the results of theoretical
calculations discussed below.
The IR spectrum of 6 in solution displays two C−O stretches
with a pattern (weak and strong, in order of decreasing
frequency) characteristic of transoid M2(CO)2 oscillators
having essentially antiparallel CO ligands,23 as found in parent
complex 1 (Table 1). The MoCp fragments of the molecule,
however, are inequivalent, as revealed by the observation of
distinct NMR resonances for the pairs of CO and Cp ligands
(see the Experimental Section), and the chemical shifts of the
bridgehead atoms of the phosphanyl (δP 155.5 ppm) and
iminoacyl (δC 189.9 ppm) ligands are comparable to those of
the corresponding atoms in alkenyl complex 5. The resonances
for the bridgehead carbon atom in these two compounds,
however, differ substantially in their two-bond coupling to the P
atom, being negligible in alkenyl complex 5 but relatively high
for 6 (JPC = 23 Hz), and this indicates that the P−Mo−C angles
involving the bridgehead carbon in both compounds probably
differ substantially from each other.24
We have previously prepared formimidoyl- and iminoacyl-
bridged complexes related to compound 6 through insertion of
isocyanides into unsaturated hydride- and alkyl-bridged
complexes of the type [M2Cp2(μ-X)(μ-PCy2)(CO)2] (M =
Mo and W; X = H, Me).25,26 In most cases, the coordination of
the C,N-donor ligand in these compounds corresponds to the
5-electron donor μ-η2:η2 mode (A in Chart 2), which in these
cases allows the dimetal center to reach electronic saturation.
The bridgehead carbon atom in this coordination mode is
characterized by a relatively shielded 13C NMR resonance
around 60 ppm which displays a substantial P−C coupling of
Chart 2
Reaction of 1 with Alkynes. Compound 1 reacts at 333 K
in toluene solution with an activated terminal alkyne such as
methyl propiolate to give the corresponding propenylylidene
derivative [Mo2Cp2{μ-κ2:η3-CPhCHC(CO2Me)}(μ-PCy2)-
(CO)2] (7a), a species following from selective coupling of
the carbyne ligand to the terminal carbon of the alkyne
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Mo2Cp2 platform of 7b takes place under these conditions to
give cis-dicarbonyl isomer cis-[Mo2Cp2{μ-κ2:η3-CPhC-
(CO2Me)C(CO2Me)}(μ-PCy2)(CO)2] (cis-7b) in a selective
way (Scheme 3).
Structural Characterization of Propenylylidene De-
rivatives 7. The structure of compound 7a was determined by
an X-ray study during our preliminary exploration on the
chemistry of 1 (Figure 3)11 and turned out to be very similar to
Figure 2. DFT-optimized structures of different isomers of compound
6 with the iminoacyl ligand in coordination modes A and B, with H
atoms omitted. Relative Gibbs free energies were 15.9 (6A1), 38.5
(6A2) and 0.0 kJ/mol (6B).
Figure 3. ORTEP drawing (30% probability) of compound 7a, with H
atoms (except H10) and cyclohexyl rings (except the C1 atoms)
omitted for clarity.11 Selected bond lengths (Å) and angles (deg):
Mo1−Mo2 = 2.8349(5), Mo1−P1 = 2.475(1), Mo1−C1 = 1.971(5),
Mo1−C3 = 2.399(4), Mo1−C10 = 2.279(5), Mo1−C11 = 2.198(5),
Mo2−P1 = 2.416(1), Mo2−C2 = 1.991(5), Mo2−C3 = 2.184(4),
Mo2−C11 = 2.193(5), C3−C10 = 1.402(6), C10−C11 = 1.446(6),
C11−C12 = 1.458(7), C12−O3 = 1.210(6), C12−O4 = 1.350(6);
Mo2−Mo1−C1 = 117.9(1), Mo1−Mo2−C2 = 84.0(1).
(Scheme 3). Related complex [Mo2Cp2{μ-κ2:η3-CPhC-
(CO2Me)C(CO2Me)}(μ-PCy2)(CO)2] (7b) could be ob-
tained when using the internal alkyne dimethyl acetylenedi-
carboxylate, although in that case the reaction had to be carried
out at 393 K to overcome the higher steric barrier involved in
the corresponding C−C coupling. In any case, we note that this
behavior is comparable to the one previously found for related
carbyne-bridged complexes such as dimolybdenum complex
[Mo2Cp2(μ-COMe)(μ-PCy2)(CO)2]28 or heterometallic
[FeMoCp{μ-C(p-tol)}(CO)5].29
that of trans-[Mo2Cp2{μ-κ2:η3-C(OMe)CHC(p-tol)}(μ-PCy2)-
(CO)2], a molecule which we have discussed in detail
previously;28 therefore, no further discussion on the structural
aspects of compounds 7 is needed.
Spectroscopic data in solution for 7a and 7b (Table 1 and
Experimental Section) are similar to each other and consistent
with the solid-state structure of the former, thus indicating
retention of this structure in solution. These data are also
comparable to those previously reported for related propeny-
lylidene complexes of the type [Mo2Cp2{μ-κ2:η3-C(OMe)-
CRCR′}(μ-PCy2)(CO)2] and will not be discussed in detail.
We note that the symmetric C−O stretch for 7a is now of
strong (instead of weak) intensity, in agreement with the angle
of ca. 150° defined by the carbonyl ligands in its quite distorted
transoid Mo2(CO)2 oscillator. However, the symmetric stretch
for 7b is weaker, indicative of the presence of a less distorted
transoid Mo2(CO)2 oscillator in that case. We also note for
both compounds the quite different coupling to P of the
bridging C atoms of the hydrocarbon chain, negligible for the
C(Ph) atom and of ca. 25 Hz for the C(CO2Me) atom, in
agreement with the much more acute P−Mo−C angle in the
latter case (average values in the solid-state structure of 7a are
ca. 105 and 78°, respectively).24
In an attempt to test the reversibility of the C−C coupling
process leading to complexes 7, we irradiated tetrahydrofuran
solutions of 7b with visible−UV light in the hope that an
hypothetical decarbonylation could in turn trigger a C−C
cleavage process. Instead, a full trans to cis isomerization of the
Scheme 3
Spectroscopic data for cisoid isomer cis-7b are comparable to
those of its transoid isomer 7b, but there are two significant
differences. First, the symmetric C−O stretch is now much
stronger than the asymmetric one, as expected for a M2(CO)2
oscillator having almost parallel CO ligands.23 The second
3502
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Article
1
spectroscopic difference is unexpected: The H and 13C NMR
spectra indicate that both MoCp(CO) fragments of the
molecule are apparently equivalent, which is inconsistent with
the asymmetric coordination of the propenylylidene ligand in
this complex, and this situation remained the same on cooling
the solution down to 183 K. We have previously encountered
the same situation in related methoxy-substituted complex cis-
[Mo2Cp2{μ-κ2:η3-C(OMe)CRCR}(μ-PCy2)(CO)2] (R =
CO2Me)28 and have interpreted it as resulting from a fluxional
process whereby the central C atom of the hydrocarbon chain
(C10 in Figure 3) binds alternatively each of the Mo atoms, a
rearrangement which yields, on the fast exchange limit,
equivalent environments for the pairs of CO and Cp ligands.
(0.058 g, 90%). Anal. Calcd for C44H47Mo2N2O2P: C, 61.54; H, 5.52;
N, 3.26. Found: C, 61.78; H, 5.32; N, 3.11. 1H NMR δ 7.49−7.36 (m,
8H, Ph), 7.32−7.22 (m, 4H, Ph), 7.04 [t, JHH = 7, 1H, H4(Ph)], 6.80
[false d, JHH = 7, 2H, H2(Ph)], 5.09, 4.72 (2s, 2 × 5H, Cp), 2.60−1.20
(m, 21H, Cy), 0.82 (m, 1H, Cy). 13C{1H} NMR δ 234.4 (d, JCP = 12,
MoCO), 226.0 [s, μ-CPh(CO)], 166.7 [s, C1(Ph)], 149.9 [s,
2C1(Ph)], 136.5 (s, N2CPh2), 134.4 (s, μ-CPh), 131.4, 130.2, 130.0,
129.5, 128.9, 128.6, 128.3, 128.3, 124.7 (9s, Ph), 99.0, 91.1 (2s, Cp),
56.0 [d, JCP = 11, C1(Cy)], 51.8 [d, JCP = 17, C1(Cy)], 37.3 [s,
C2(Cy)], 37.0 [d, JCP = 5, C2(Cy)], 35.2 [d, JCP = 3, C2(Cy)], 35.1 [d,
JCP = 6, C2(Cy)], 29.3 [d, JCP = 10, C3(Cy)], 29.0 [d, JCP = 9, C3(Cy)],
28.9 [d, JCP = 13, C3(Cy)], 28.6 [d, JCP = 9, C3(Cy)], 26.9 [s,
2C4(Cy)].
Preparation of cis-[Mo2Cp2{μ-κ1:η2-C(Ph)CO}(μ-PCy2)(CO)(κ1-
N2CPh2)] (cis-3). Et2O solution of N2CPh2 (3 mL of a 0.08 M
solution, 0.24 mmol) was added to a solution of compound 2 (0.050 g,
0.072 mmol) in dichloromethane (2 mL), and the mixture was stirred
for 5 min at room temperature to give a black-greenish solution. The
solvent was then removed under vacuum, the residue extracted with
dichloromethane/petroleum ether (1/10), and the extracts chromato-
graphed on alumina at 288 K. Elution with dichloromethane/
petroleum ether (1/1) gave a dark green fraction yielding, after
removal of solvents, compound cis-3 as a green-black microcrystalline
solid (0.055 g, 89%). Anal. Calcd for C44H47Mo2N2O2P: C, 61.54; H,
CONCLUDING REMARKS
■
The electronic and coordinative unsaturation of dicarbonyl
complex 1 facilitates the coordination to its dimetal center of
small unsaturated organic molecules such as diazoalkanes,
azides, and activated alkynes under mild conditions, whereby
new molecules of low thermal stability can be prepared, as is
the case of alkenyl complex 5, iminocyl complex 6, or even
ketenyl complex 3. Coupling of the carbyne ligand to the
incoming molecule is strongly favored in the case of activated
alkynes, but for diazoalkanes and azides, such a process seems
to be linked to denitrogenation. Otherwise, no reaction
(azides) or carbyne-carbonyl coupling (diazoalkanes) takes
place instead.
1
5.52; N, 3.26. Found: C, 61.25; H, 5.35; N, 3.02. H NMR δ 7.58−
7.56 (m, 2H, Ph), 7.42−7.25 (m, 10H, Ph), 7.06−7.02 (m, 3H, Ph),
5.10, 4.93 (2s, 2 × 5H, Cp), 2.60−2.59 (m, 2H, Cy), 2.36−2.27 (m,
2H, Cy), 2.00−1.20 (m, 18H, Cy). 13C{1H} NMR (100.61 MHz) δ
232.1 (d, JCP = 12, MoCO), 216.4 [s, μ-CPh(CO)], 151.6 (s,
N2CPh2), 150.2, 137.0 [2s, 3C1(Ph)], 132.7 (s, μ-CPh), 130.4, 130.1,
129.6, 128.9, 128.7, 128.4, 128.1, 128.1, 124.6 (9s, Ph), 100.1, 89.9 (2s,
Cp), 52.2 [d, JCP = 22, C1(Cy)], 46.6 [d, JCP = 10, C1(Cy)], 35.1, 34.8
[2s, 2C2(Cy)], 33.6 [d, JCP = 5, C2(Cy)], 33.1 [s, C2(Cy)], 28.7 [d, JCP
= 10, C3(Cy)], 28.5 [d, JCP = 11, C3(Cy)], 28.3 [d, JCP = 12, C3(Cy)],
28.1 [d, JCP = 12, C3(Cy)] 27.0, 26.9 [2s, 2C4(Cy)].
EXPERIMENTAL SECTION
■
General Procedures and Starting Materials. All manipulations
and reactions were carried out under a nitrogen (99.995%)
atmosphere using standard Schlenk techniques. Solvents were purified
according to literature procedures, and distilled prior to use.30
Compounds 1 and 2,8 N2CPh2,31 and Et2O solutions of CH2N2,32
were prepared as described previously, and all other reagents were
obtained from the usual commercial suppliers and used as received,
unless otherwise stated. Petroleum ether refers to that fraction
distilling in the range 338−343 K. Photochemical experiments were
performed using jacketed Pyrex Schlenk tubes cooled by tap water (ca.
288 K). A 400 W medium-pressure mercury lamp placed ca. 1 cm
away from the Schlenk tube was used for these experiments. Filtrations
were carried out through diatomaceous earth unless otherwise
indicated. Chromatographic separations were carried out using
jacketed columns refrigerated by tap water (ca. 288 K) or by a closed
2-propanol circuit kept at the desired temperature with a cryostat.
Commercial aluminum oxide (activity I, 70−290 mesh) was degassed
under vacuum prior to use. The latter was mixed afterward under
nitrogen with the appropriate amount of water to reach activity IV. IR
stretching frequencies of CO ligands were measured in solution using
CaF2 windows. NMR spectra were routinely recorded at 300.13 (1H),
121.50 (31P{1H}), and 75.47 MHz (13C{1H}) at 295 K in CD2Cl2
solution unless otherwise stated. Chemical shifts (δ) are given in parts
per million, relative to internal tetramethylsilane (1H, 13C) or external
85% aqueous H3PO4 (31P). Coupling constants (J) are given in Hertz.
Preparation of [Mo2Cp2{μ-κ1:η2-C(Ph)CO}(μ-PCy2)(CO)(κ1-
N2CPh2)] (3). Et2O solution of N2CPh2 (3 mL of a 0.08 M solution,
0.24 mmol) was added to a solution of compound 1 (0.050 g, 0.075
mmol) in dichloromethane (5 mL), and the mixture was stirred for 5
min. Solvents were then removed under vacuum, the residue dissolved
in dichloromethane, the tube cooled at 77 K, evacuated under vacuum,
and then refilled with CO and closed. The mixture was then stirred
while allowing it to reach room temperature slowly for 2 h, to give a
green solution which was concentrated under vacuum and then
chromatographed through alumina at 288 K. Elution with dichloro-
methane/petroleum ether (1/4) gave a green fraction yielding, after
removal of solvents, compound 3 as a green microcrystalline solid
Preparation of [Mo2Cp2(μ-CPh)(μ-PCy2)(CO)(κ1-N2CPh2)] (4).
Et2O solution of N2CPh2 (3 mL of a 0.08 M solution, 0.24 mmol) was
added to a solution of compound 1 (0.050 g, 0.075 mmol) in
dichloromethane (5 mL). Solvents were then removed under vacuum,
the oily residue dissolved in toluene, and the mixture stirred at 353 K
for 30 min to give a dark brown solution. The solvent was then
removed under vacuum, the residue extracted with dichloromethane,
and the extract chromatographed through alumina at 288 K. Elution
with dichloromethane/petroleum ether (1/9) gave a brown fraction
yielding, after removal of solvents, compound 4 as a brown powder
(0.058 g, 93%). Anal. Calcd for C43H47Mo2N2OP: C, 62.17; H, 5.70;
N, 3.37. Found: C, 61.85; H, 5.57; N, 3.45. 1H NMR (400.13 MHz) δ
7.53 [m, 1H, H4(Ph)], 7.40 [false t, JHH = 7, 2H, H3(Ph)], 7.35−7.32
(m, 3H, Ph), 7.26−7.24 (m, 6H, Ph), 7.09 [t, JHH = 7, 1H, H4(Ph)],
6.76 [false d, JHH = 7, 2H, H2(Ph)], 5.39, 5.05 (2s, 2 × 5H, Cp), 2.74
(d, br, JHP = 12, 1H, Cy), 2.20−1.20 (m, 21H, Cy). 13C{1H} NMR
(100.61 MHz) δ 373.5 (d, JCP = 6, μ-CPh), 248.5 (d, JCP = 10,
MoCO), 165.4, 148.2, 137.9 [3s, C1(Ph)], 133.9 (s, N2CPh2), 129.6,
129.3, 124.2 [3s, C4(Ph)], 129.5, 128.8, 128.6, 127.7, 127.6, 123.1 [6s,
C2,3(Ph)], 98.9, 91.6 (2s, Cp), 50.0 [d, J CP = 18, C1(Cy)], 48.0 [s, br,
C1(Cy)], 37.4 [s, C2(Cy)], 34.7 [d, JCP = 2, C2(Cy)], 34.6, 33.4 [2s,
C2(Cy)], 29.1 [d, JCP = 12, C3(Cy)], 28.7 [d, JCP = 11, C3(Cy)], 28.5
[d, JCP = 10, C3(Cy)], 28.4 [d, JCP = 11, C3(Cy)], 26.8, 26.7 [2s,
C4(Cy)].
Preparation of cis-[Mo2Cp2(μ-CPh)(μ-PCy2)(CO)(κ1-N2CPh2)]
(cis-4). Et2O solution of N2CPh2 (3 mL of a 0.08 M solution, 0.24
mmol) was added to a solution of compound 2 (0.050 g, 0.072 mmol)
in dichloromethane (2 mL), and the mixture was stirred at room
temperature for 5 min to give a dark green solution. Solvent was then
removed under vacuum, the residue dissolved in toluene, and the
mixture stirred at 353 K for 30 min to give a dark brown solution
containing a mixture of isomers 4 and cis-4 (ca. 1/5). The solvent was
then removed under vacuum, the residue extracted with dichloro-
methane/petroleum ether (1/10), and the extracts chromatographed
through alumina at 253 K. Elution with dichloromethane/petroleum
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Article
ether (1/9) gave a brown fraction yielding, after removal of solvents,
compound 4 as a brown powder (0.008 g, 13%). Elution with
dichloromethane/petroleum ether (1/8) gave a yellow-brown fraction
yielding analogously compound cis-4 as a yellow-brown powder (0.045
g, 75%). Anal. Calcd for C43H47Mo2N2OP: C, 62.17; H, 5.70; N, 3.37.
Found: C, 61.80; H, 5.43; N, 3.13. 1H NMR δ 7.79 [m, 1H, H4(Ph)],
7.59 [t, JHH = 7, 1H, H4(Ph)], 7.47 [false t, JHH = 7, 2H, H3(Ph)],
7.46−7.15 (m, 8H, Ph), 6.99 [t, JHH = 7, 1H, H4(Ph)], 6.43 [false d,
JHH = 7, 2H, H2(Ph)], 5.40, 4.90 (2s, 2 × 5H, Cp), 2.60−0.90 (m,
22H, Cy).
4H, H2,3(Ph)], 7.12 [t, JHH = 7, 1H, H4(Ph)], 6.79 (d, JHP = 2, 1H,
CH), 5.11, 4.65 (2s, 2 × 5H, Cp), 3.54 (s, 3H, OMe), 2.30−0.90 (m,
22H, Cy). 13C{1H} NMR δ 251.6 (d, JCP = 12, MoCO), 233.3 (d, JCP
= 6, MoCO), 177.2 (s, CO2Me), 145.9 [s, C1(Ph)], 137.7 (s, μ-CPh),
128.3, 127.0 [2s, C2,3(Ph)], 126.8 [s, C4(Ph)], 92.1 (d, JCP = 5,
MoCH), 91.2, 88.1 (2s, Cp), 78.4 (d, JCP = 28, μ-CCO2Me), 51.4 (s,
OMe), 51.3 [d, JCP = 14, C1(Cy)], 47.0 [d, JCP = 5, C1(Cy)], 37.8 [s,
C2(Cy)], 36.5 [d, JCP = 6, C2(Cy)], 35.5 [d, JCP = 3, C2(Cy)], 35.2 [d,
JCP = 6, C2(Cy)], 29.6, 29.1 [2d, JCP = 12, C3(Cy)], 28.8 [d, JCP = 8,
C3(Cy)], 28.6 [d, JCP = 12, C3(Cy)], 27.1, 26.9 [2s, C4(Cy)].
Preparation of [Mo2Cp2{μ-κ2:η3-CPhC(CO2Me)C(CO2Me)}(μ-
PCy2)(CO)2] (7b). Neat C2(CO2Me)2 (50 μL, 0.407 mmol) was
added to a solution of compound 1 (0.050 g, 0.075 mmol) in toluene
(10 mL), and the mixture was stirred at 393 K for 7 h to give a brown-
orange solution. The solvent was then removed under vacuum, the
residue extracted with dichloromethane/petroleum ether (1/10), and
the extracts chromatographed through alumina at 288 K. Elution with
dichloromethane/petroleum ether (1/1) gave an orange fraction
yielding, after removal of solvents, compound 7b as an orange
microcrystalline solid (0.040 g, 66%). Anal. Calcd for C37H43Mo2O6P:
C, 55.10; H, 5.37. Found: C, 55.42; H, 5.36. 1H NMR δ 7.20−7.14 (m,
2H, Ph), 7.12−7.06 (m, 3H, Ph), 5.12, 5.07 (2s, 2 × 5H, Cp), 3.61,
3.37 (2s, 2 × 3H, OMe), 2.37 (m, 1H, Cy), 2.40−0.60 (m, 21H, Cy).
13C{1H} NMR (100.61 MHz) δ 248.0 (d, JCP = 11, MoCO), 232.5 (d,
Preparation of [Mo2Cp2{μ-κ1:η2-C(Ph)CH2}(μ-PCy2)(CO)2] (5).
Et2O solution of N2CH2 (2 mL of a 0.07 M solution, 0.14 mmol) was
added to a solution of compound 1 (0.050 g, 0.075 mmol) in
dichloromethane (5 mL), and the mixture was stirred at room
temperature for 5 min. Solvents were then removed under vacuum, the
brown residue extracted with dichloromethane/petroleum ether (1/
10), and the extracts chromatographed through alumina at 288 K.
Elution with dichloromethane/petroleum ether (1/8) gave a greenish
brown fraction yielding, after removal of solvents, compound 5 as a
brown solid (0.045 g, 88%). Attempts to grow single crystals of this
complex were unsuccessful due to its progressive transformation in
solution into a mixture of two isomers not characterized (see text).
Anal. Calcd for C32H39Mo2O2P: C, 56.65; H, 5.79. Found: C, 56.30;
H, 5.45. 1H NMR δ 7.16 [false t, JHH = 7, 2H, H3(Ph)], 7.05 [t, JHH
=
J
CP = 7, CO), 175.4 (s, 2CO2Me), 140.4 [s, C1(Ph)], 128.7, 127.5 [2s,
7, 1H, H4(Ph)], 6.88 [false d, JHH = 7, 2H, H2(Ph)], 5.29 (s, 5H, Cp),
5.13 (d, JHH = 2.2, 1H, CH2), 5.09 (s, 5H, Cp), 5.09 (d, JHH = 2.2, 1H,
CH2), 2.47−2.43 (m, 2H, Cy), 2.35 (m, 1H, Cy), 1.92−1.12 (m, 19H,
Cy). 13C{1H} NMR δ 246.6 (d, JCP = 14, MoCO), 246.5 (d, JCP = 10,
MoCO), 182.0 (s, μ-CPh), 152.0 [s, C1(Ph)], 128.9 [s, C4(Ph)],
128.1, 127.3 [2s, C2,3(Ph)], 90.8, 89.6 (2s, Cp), 68.3 (s, CH2), 49.8 [d,
JCP = 22, C1(Cy)], 41.5 [d, JCP = 16, C1(Cy)], 34.8 [d, JCP = 4,
C2(Cy)], 34.6 [d, JCP = 2, C2(Cy)], 34.3 [d, JCP = 1, C2(Cy)], 34.0 [d,
JCP = 5, C2(Cy)], 28.8 [d, JCP = 12, C3(Cy)], 28.3 [d, JCP = 14,
C3(Cy)], 28.2 [d, JCP = 10, 2C3(Cy)], 26.7, 26.5 [2s, C4(Cy)].
Preparation of [Mo2Cp2{μ-C(Ph)NCH2Ph}(μ-PCy2)(CO)2] (6).
Neat N3CH2Ph (15 μL, 0.12 mmol) was added to a solution of
compound 1 (0.050 g, 0.075 mmol) in dichloromethane (5 mL), and
the mixture was stirred at room temperature for 5 min (Caution:
Benzyl azide is a flammable liquid and forms explosive vapor/air
mixtures). The solvent was then removed under vacuum, the residue
kept under vacuum for 1 h and then extracted with dichloromethane/
petroleum ether (1/10), and the extracts chromatographed through
alumina at 263 K. Elution with dichloromethane/tetrahydrofuran (9/
1) gave a brown fraction yielding, after removal of solvents, compound
6 as a brown microcrystalline solid (0.050 g, 86%). Attempts to grow
single crystals of this complex were unsuccessful due to its progressive
transformation in solution into a mixture of different products not
characterized. Anal. Calcd for C39H46Cl2Mo2NO2P (6·CH2Cl2): C,
C2,3(Ph)], 126.3 [s, C4(Ph)], 112.1 [d, J CP = 4, C(CO2Me)], 101.0 (s,
μ-CPh), 91.2, 89.0 (2s, Cp), 80.0 [d, JCP = 24, μ-C(CO2Me)], 53.3 [d,
JCP = 16, C1(Cy)], 51.7, 51.0 (2s, OMe), 46.7 [d, JCP = 2, C1(Cy)],
38.0 [s, C2(Cy)], 36.3 [d, JCP = 7, C2(Cy)], 35.3, 35.0 [2s, C2(Cy)],
29.5 [d, JCP = 11, C3(Cy)], 28.9 [d, JCP = 10, C3(Cy)], 28.8 [d, JCP
=
12, 2C3(Cy)], 27.0, 26.8 [2s, C4(Cy)].
Preparation of cis-[Mo2Cp2{μ-κ2:η3-CPhC(CO2Me)C(CO2Me)}-
(μ-PCy2)(CO)2] (cis-7b). A solution of compound 7b (0.050 g, 0.062
mmol) in tetrahydrofuran (5 mL) was irradiated with visible−UV light
for 20 min at 288 K to give a yellow solution. Workup as described for
7b yielded compound cis-7b as an orange microcrystalline solid (0.042
g, 84%). Anal. Calcd for C37H43Mo2O6P: C, 55.10; H, 5.37. Found: C,
49.82; H, 5.12. 1H NMR δ 7.26−7.15 [m, 3H, H3,4(Ph)], 6.85 [false d,
JHH = 8, 2H, H2(Ph)], 5.15 (s, 10H, Cp), 3.45, 3.42 (2s, 2 × 3H,
OMe), 1.90−1.10 (m, 22H, Cy). 13C{1H} NMR (100.61 MHz) δ
236.1 (d, J CP = 10, 2MoCO), 177.8 (d, JCP = 3, CO2Me), 177.5 (s, CO
2Me), 137.9 [s, C1(Ph)], 128.3, 127.9 [2s, C2,3(Ph)], 127.4 [s,
C4(Ph)], 126.0 [d, J
= 4, C(CO2Me)], 99.5 (s, μ-CPh), 89.3 (s,
CP
2Cp), 63.7 [d, JCP = 30, μ-C(CO 2Me)], 51.6, 51.5 (2s, OMe), 49.3 [d,
JCP = 16, C1(Cy)], 45.0 [d, JCP = 8, C1(Cy)], 35.5 [d, JCP = 3, C2(Cy)],
34.8 [d, JCP = 4, C2(Cy)], 28.8, 28.5 [2d, J = 10, C3(Cy)], 26.6 [s,
CP
2C4(Cy)].
Computational Details. All DFT computations were carried out
using the Gaussian09 package,33 in which the hybrid method B3LYP
was used with the Becke three-parameter exchange functional34 and
the Lee−Yang−Parr correlation functional.35 An accurate numerical
integration grid (99 590) was used for all the calculations via the
keyword Int = Ultrafine. Effective core potentials and their associated
double-ζ LANL2DZ basis set were used for the metal atoms.36 The
light elements (P, O, C, and H) were described with the 6-31G*
basis.37 Geometry optimizations were performed under no symmetry
restrictions, and frequency analyses were performed for all the
stationary points to ensure that minimum structures with no imaginary
frequencies were achieved. NMR shielding contributions and coupling
constants were calculated using the gauge-including atomic orbitals
(GIAO) method,38 in combination with the LANL2DZ basis set for
the Mo atoms and the 6-311+G(2d,p) basis set for the remaining
atoms.39
1
54.82; H, 5.43; N, 1.64. Found: C, 54.44; H, 5.53; N, 1.81. H NMR
(400.13 MHz, 253 K) δ 7.39−7.35 (m, 3H, Ph), 7.30−7.24 (m, 6H,
Ph), 7.02 [tt, JHH = 7, 1.5, 1H, H4(Ph)], 5.10, 5.04 (2s, 2 × 5H, Cp),
4.92, 4.81 (2d, JHH = 13, 2 × 1H, NCH2), 2.18−1.05 (m, 22H, Cy).
13C{1H} NMR (100.61 MHz, 253 K) δ 257.9 (d, JCP = 11, MoCO),
244.7 (d, JCP = 7, MoCO), 189.9 (d, JCP = 23, μ-CPh), 158.5, 136.4
[2s, 2C1(Ph)], 129.4, 129.0, 128.4, 127.3, 126.7, 124.6 (6s, Ph), 92.7,
91.8 (2s, Cp), 70.0 (s, NCH2), 54.4 [d, JCP = 12, C1(Cy)], 50.0 [s,
C1(Cy)], 36.9 [d, JCP = 6, C2(Cy)], 35.4, 35.1 [2d, JCP = 4, C2(Cy)],
34.7 [d, JCP = 6, C2(Cy)], 29.3 [d, JCP = 11, C3(Cy)], 29.1, 28.6, 28.5
[3d, JCP = 10, C3(Cy)], 26.9, 26.6 [2s, C4(Cy)].
Preparation of [Mo2Cp2{μ-κ2:η3-CPhCHC(CO2Me)}(μ-PCy2)-
(CO)2] (7a). Neat methyl propiolate (40 μL, 0.45 mmol) was added
to a solution of compound 1 (0.050 g, 0.075 mmol) in toluene (10
mL), and the mixture was stirred at 333 K for 2 h to give an orange
solution. The solvent was then removed under vacuum, the residue
extracted with dichloromethane/petroleum ether (1/10), and the
extracts chromatographed through alumina at 288 K. Elution with
dichloromethane/petroleum ether (1/4) gave an orange fraction
yielding, after removal of the solvents, compound 7a as an orange
microcrystalline solid (0.041 g, 73%). Anal. Calcd for C35H41Mo2O4P:
C, 56.16; H, 5.52. Found: C, 56.46; H, 5.71. 1H NMR δ 7.34−7.25 [m,
ASSOCIATED CONTENT
■
S
* Supporting Information
The Supporting Information is available free of charge on the
ACS Publications website at DOI: 10.1021/acs.organo-
met.6b00552.
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DOI: 10.1021/acs.organomet.6b00552
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Organometallics
Results of DFT calculations (drawings, energies,
Article
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Chem. Soc., Chem. Commun. 1990, 170−172. (d) Tang, Y.; Sun, J.;
Chen, J. Organometallics 1998, 17, 2945−2952. (e) Tang, Y.; Sun, J.;
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N.; Xu, Q.; Tsumori, N.; Sun, J.; Yin, Y.; Chen, J. Organometallics
2003, 22, 4369−4371.
Cartesian coordinates, and NMR parameters for different
isomers of compound 6) (PDF)
Cartesian coordinates for compound 6 (XYZ)
AUTHOR INFORMATION
Corresponding Author
*E-mail: mara@uniovi.es.
(17) Fischer, E. O.; Kellerer, W.; Zimmer-Gasser, B.; Schubert, U. J.
Organomet. Chem. 1980, 199, C24−C26.
■
(18) García, M. E.; Riera, V.; Ruiz, M. A.; Rueda, M. T.; Sae
́
z, D.
Organometallics 2002, 21, 5515−5525.
Notes
(19) Alvarez, M. A.; García, M. E.; García-Vivo,
́
D.; Menen
́
dez, S.;
The authors declare no competing financial interest.
Ruiz, M. A. Organometallics 2013, 32, 218−231.
(20) Adatia, T.; McPartlin, M.; Mays, M. J.; Morris, M. J.; Raithby, P.
R. J. Chem. Soc., Dalton Trans. 1989, 1555−1564.
ACKNOWLEDGMENTS
We thank the MINECO of Spain for financial support (Project
CTQ2012-33187), the Consejeria de Educacion
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(21) Alvarez, M. A.; García, M. E.; Riera, V.; Ruiz, M. A.; Robert, F.
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