Reversible pyranyl complex formation and the mechanism of rearrangement to (η5-6-oxocycloheptadienyl)Mn(CO)3 complexes in the reaction of β-cyclomanganated 1,5-diarylpenta-1,4-dien-3-ones and alkynes; The crystal structure of [2,4-diphenyl-6-(2-phenylethenyl)pyranyl- η5]tricarbonylmanganese

Article abstract of DOI:10.1016/j.jorganchem.2005.04.015

[1-Phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-κO]ethenyl-κC ¹]tetracarbonylmanganese (1a) reacts with PhCCH in CCl₄ at room temperature to form [2,4-diphenyl-6-(2-phenylethenyl)pyranyl- η⁵]tricarbonylmanganese (2a), whose X-ray crystal structure is reported to complement that of its isomer [6-oxo-2,4,7-triphenylcyclohepta-1,4- dienyl-1,2,3,4,5-η]tricarbonylmanganese (3a), previously obtained from the reaction under reflux; but for 1a and PhCCPh the pyranyl complex cannot be isolated before rearrangement to the 3a analogue occurs. More forcing reaction conditions for 1a with Me₃SiCCH and for [1-(2-trifluoromethylphenyl)- 2-[(E)-3-(2-trifluoromethylphenyl)prop-2-en-1-oyl-κO]ethenyl-κC ¹]tetracarbonylmanganese (1b) with Me₃SiCCH and PhCCH give new analogues of 3a where previously only 2a analogues had been isolated. The reaction in CCl₄ under reflux of PhCCH and the β-deuterio analogue of 1a, [1-phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-3d-κO]ethenyl- κC¹]tetracarbonylmanganese, gave deuteriated 3a with exo-D at the α-carbon, C7. This is inconsistent with the Mn-mediated Ph migration mechanism originally proposed to accommodate the endo position of Ph in 3a, and instead it implicates a cyclopropyl carbonyl-addition intermediate or a cyclopropyl acyl-substitution transition state in the key rearrangement step for 2a → 3a.

Full text of DOI:10.1016/j.jorganchem.2005.04.015

Journal of Organometallic Chemistry 690 (2005) 3340–3347
www.elsevier.com/locate/jorganchem
Reversible pyranyl complex formation and the mechanism
of rearrangement to (g5-6-oxocycloheptadienyl)Mn(CO)3
complexes in the reaction of b-cyclomanganated
1,5-diarylpenta-1,4-dien-3-ones and alkynes; the crystal structure
of [2,4-diphenyl-6-(2-phenylethenyl)pyranyl-g5]tricarbonylmanganese
*
Wade J. Mace, Lyndsay Main , Brian K. Nicholson
Chemistry Department, University of Waikato, Private Bag 3105, Hamilton, New Zealand
Received 25 February 2005; accepted 5 April 2005
Available online 31 May 2005
Abstract
[1-Phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-jO]ethenyl-jC1]tetracarbonylmanganese (1a) reacts with PhCCH in CCl4 at room
temperature to form [2,4-diphenyl-6-(2-phenylethenyl)pyranyl-g5]tricarbonylmanganese (2a), whose X-ray crystal structure is
reported to complement that of its isomer [6-oxo-2,4,7-triphenylcyclohepta-1,4-dienyl-1,2,3,4,5-g]tricarbonylmanganese (3a), previ-
ously obtained from the reaction under reflux; but for 1a and PhCCPh the pyranyl complex cannot be isolated before rearrangement
to the 3a analogue occurs. More forcing reaction conditions for 1a with Me3SiCCH and for [1-(2-trifluoromethylphenyl)-2-[(E)-3-(2-
trifluoromethylphenyl)prop-2-en-1-oyl-jO]ethenyl-jC1]tetracarbonylmanganese (1b) with Me3SiCCH and PhCCH give new ana-
logues of 3a where previously only 2a analogues had been isolated.
The reaction in CCl4 under reflux of PhCCH and the b-deuterio analogue of 1a, [1-phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-3d-
jO]ethenyl-jC1]tetracarbonylmanganese, gave deuteriated 3a with exo-D at the a-carbon, C7. This is inconsistent with the Mn-med-
iated Ph migration mechanism originally proposedto accommodate the endopositionof Ph in 3a, andinstead itimplicates a cyclopropyl
carbonyl-addition intermediate or a cyclopropyl acyl-substitution transition state in the key rearrangement step for 2a ! 3a.
ꢀ 2005 Elsevier B.V. All rights reserved.
Keywords: Manganese; Alkyne; Cyclometallation; Crystal structure; Mechanism; Addition–elimination; Acyl substitution
1. Introduction
(e.g., 2a; Scheme 1) but also 6-oxocycloheptadienyl com-
plexes (e.g., 3a). The latter were suggested to be formed
via an insertion intermediate (4b or 4c) with metal coor-
dination alternative to that in the assumed precursor 4a
(Scheme 2) of the pyranyl complex.
Reversible formation of the pyranyl complex was
indicated by the observation that while 1a with PhCCH
gave only oxocycloheptadienyl complex 3a as the isola-
ble product after 24 h, the initial formation and then dis-
appearance of some pyranyl complex 2a was detected by
IR monitoring during the course of the reaction. An-
other 24-h reaction which gave no pyranyl complex
Following an early review [1] incorporating the cou-
pling of alkynes with cyclomanganated aryl carbonyl
compounds, we reported [2a] that reactions of alkynes
with b-cyclomanganated chalcones in CCl4 under reflux
give (g5-pyranyl)Mn(CO)3 complexes. The reaction was
more recently studied with b-cyclomanganated dienones
(1) and shown [2b] to give not only pyranyl complexes
*
Corresponding author. Tel.: +64 78 384 385; fax: +64 78 384 219.
E-mail address: l.main@waikato.ac.nz (L. Main).
0022-328X/$ - see front matter ꢀ 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2005.04.015

W.J. Mace et al. / Journal of Organometallic Chemistry 690 (2005) 3340–3347
3341
R1
R1
heptadienyl ring). A tracer study using 1a labeled with
D at the b-position now allows a distinction between
this and an alternative rearrangement mechanism start-
ing from 4c previously considered [2b] and leads to a
major mechanism reassessment.
β
Mn
(CO)4
O
1a R1 = H
1b R1 =CF3
R3C CR4
2. Results and discussion
2''
R1
2'
R1
4
H
O
1'
2.1. Product formation under modified reaction conditions
R1
2'''
6''
H
or
6
6
H
R1
7
1
O
2
1
R3
4
The following summary shows that both pyranyl and
oxocycloheptadienyl complexes are formed from each of
the manganated dienones 1a and 1b under appropriate
conditions, and are isolable in all but one case (pyranyl
complex from 1a with PhCCPh). Over time, the rear-
rangement of pyranyl to oxocycloheptadienyl complex
occurs routinely. It seems likely on mechanism grounds
that the oxocycloheptadienyl complexes would all be
endo as for 3a, whose crystal structure has been deter-
mined [2b], but this is not proven; certainly chemical
shift comparability for H7 within and between the 3a–
c and 3d–f series suggests that all H7 are on the same
(exo) face.
2
6'''
R3
R4
R4
H
Mn
(CO)3
Mn
(CO)3
3a R1 = R3 = H; R4 = Ph
(from 1a with PhCCH)
3b R1 = R3 = H; R4 = SiMe3
(from 1a with Me3SiCCH)
3c R1 = H; R3 = R4 = Ph
(from 1a with PhCCPh)
2a R1 = R3 = H; R4 = Ph
(from 1a with PhCCH)
2b R1 = R3 = H; R4 = SiMe3
(from 1a with Me3SiCCH)
2c R1 = H; R3 = R4 = Ph
(from 1a with PhCCPh)
3d R1 = CF3; R3 = H; R4 = Ph
(from 1b with PhCCH)
3e R1 = CF3; R3 = H; R4 = SiMe3
(from 1b with Me3SiCCH)
3f R1 = CF3; R3 = R4 = Ph
(from 1b with PhCCPh)
2d R1 = CF3; R3 = H; R4 = Ph
(from 1b with PhCCH)
2e R1 = CF3; R3 = H; R4 = SiMe3
(from 1b with Me3SiCCH)
2f R1 = CF3; R3 = R4 = Ph
(from 1b with PhCCPh)
Scheme 1. Products from reactions of cyclomanganated 1,5-diaryl-
penta-1,4-dien-3-ones with alkynes.
2.1.1. Reactions of [1-phenyl-2-[(E)-3-phenylprop-2-en-
1-oyl-jO]ethenyl-jC1]tetracarbonylmanganese (1a)
Phenylacetylene. Previously [2b] this reaction in CCl4
under reflux gave only 3a though there was IR evidence
for the formation and disappearance of the pyranyl
complex 2a. Now the reaction in CCl4 at room temper-
ature for 28 h gives 2a, isolated as dark red crystals,
whose X-ray crystal structure is determined (see Sections
2.3 and 3.4) to complement that of the isomeric endo-
oxocycloheptadienyl complex 3a from the previous
study [2b].
(Trimethylsilyl)acetylene. The unknown oxocyclohep-
tadienyl complex 3b was obtained from the reaction car-
ried out now under more forcing conditions in heptane
(b.p. 98 ꢁC) under reflux for 24 h, along with an equiv-
alent amount of the pyranyl complex 2b already known
[2b] from the reaction in CCl4.
was that of 1b with PhCCPh which furnished only 3f.
However, some other reactions were allowed to proceed
only for the shorter time required for all of the manga-
nated reactant to be consumed (ca. 4 h) and in these
cases (e.g., 1a with Me3SiCCH; 1b with PhCCH and
Me3SiCCH) only the pyranyl complexes (2e, 2b, 2d)
were obtained. Reaction times in these cases were not
extended to see if rearrangement to oxocycloheptadienyl
complexes might occur over time. One of the aims of the
present study was to fill these gaps in the original explor-
atory study and determine whether reversible pyranyl
formation accompanied by rearrangement to oxocyclo-
heptadienyl complex is general under appropriate
conditions.
The second and major aim was to test the Mn-medi-
ated phenyl migration mechanism (4b ! 3a) previously
proposed [2b] to accommodate the stereochemistry of
the oxocycloheptadienyl complex 3a which is endo (7-
Ph group towards the Mn(CO)3 face of the oxocyclo-
Diphenylacetylene. This reaction had not been studied
previously but over 4 days at room temperature, forma-
tion and disappearance of 2c in only a low concentration
was observed with 3c accumulating as the only isolable
product.
Ph
Ph
Ph
O
H
O
Ph
H
β
H
H
O
H
β
H
Ph
Ph
Mn(CO)4
Ph
Ph
Mn
4a
Mn
4c
4b
Ph
Scheme 2. Alternative metal coordination modes in the insertion intermediate for 1a and phenylacetylene.

3342
W.J. Mace et al. / Journal of Organometallic Chemistry 690 (2005) 3340–3347
2.1.2. Reactions of [1-(2-trifluoromethylphenyl)-2-[(E)-
3-(2-trifluoromethyl)phenylprop-2-en-1-oyl-jO]ethenyl-
jC1]tetracarbonylmanganese (1b)
Phenylacetylene. Previously [2b] this reaction in CCl4
gave only 2d but in heptane under reflux over 24 h 3d
was obtained in 3:1 excess over 2d.
(Trimethylsilyl)acetylene. The unknown oxocyclohep-
tadienyl complex 3e was obtained from the reaction car-
ried out in heptane under reflux but even after 7 days
there was still almost a two-fold excess of the pyranyl
complex 2e, already known [2b] from the reaction in
CCl4.
Diphenylacetylene. By contrast, this reaction had ear-
lier [2b] yielded only 3f after 24 h in CCl4 under reflux.
Here the same product was obtained along with an
equivalent amount of the new pyranyl complex 2f at
30 ꢁC in heptane.
Conclusions from these results are first that the pyra-
nyl complex is always formed but it rearranges to oxocy-
cloheptadienyl complex over time, presumably through
reversal to complex 4a (Scheme 2). Second, there are
reactivity differences with substituents, e.g., for 1a with
diphenylacetylene even at room temperature, the oxocy-
cloheptadienyl complex 3c is dominant from an early
stage of the reaction, whereas for the sluggish reaction
of 1b with Me3SiCCH the pyranyl complex 2e is still
dominant over 3e after 7 days in heptane at 98 ꢁC. As
yet there are too few data to justify analysis of substitu-
ent effects.
the coordinated p-bond of intermediates 4b or 4c. These
mechanisms are repeated here in Scheme 3 and 4 but
now depicting b-deuterio-labeled 4b and 4c as obtained
from PhCCH and the b-deuterio derivative of 1a. The
latter compound (b-D-1a, systematically named [1-phe-
nyl-2-[(E)-3-phenylprop-2-en-1-oyl-3d-jO]ethenyl-jC1]-
tetracarbonylmanganese) was synthesized in the present
study (see Section 3.3 and Scheme 7) for the purpose of
distinguishing between these mechanisms.
The metal-mediated phenyl migration mechanism
(Scheme 3) was originally invoked to meet the stereo-
chemical requirement that the Ph group finishes up on
the same face as the coordinated Mn (endo) as would re-
sult if the Mn remains p-coordinated in 6 as it transfers
Ph. If this mechanism operates the D label would be in
the 6-position in 3a as shown (Scheme 3).
The alternative mechanism originally considered [2b]
was one (Scheme 4) in which the rearrangement occurs
via initial alkene addition to form a 6-membered ring
followed by ring expansion through addition of the
manganated carbon in 8 to the ketone C@O, with sub-
sequent elimination to reopen the cyclopropyl ring of
9. An analogous (but 5- to 6-membered) ring-expansion
addition–elimination mechanism through a cyclopropyl
addition intermediate (with subsequent Pd hydride elim-
ination) has been proposed for a palladiated precursor
derived from N-allyl-N-(2-bromoallyl)-4-methylben-
zenesulfonamide and Pd(PPh3)4 leading on to the
5-methylene-3,4-dihydropyridine N-(4-methylbenzene-
sulfonyl) derivative [3].
2.2. Deuterium isotopic labeling study for the mechanism
of formation of oxocycloheptadienyl complex 3a
Here the Ph group does not migrate, rather the car-
bon atom with attached phenyl group (and H, or D as
shown here) exchanges position to move adjacent to
C@O. However it was originally considered that in the
non-polar solvent, stabilisation of the alkoxide anion
by coordination to Mn as shown in 8 and 9 would be re-
We previously [2b] considered two possible mecha-
nisms for formation of 3a with the Ph group in the endo
position, starting, respectively, with syn addition across
Ph
Ph
Ph
Ph
1
D
O
O
O
O
H
H
β
D
D
H
H
H
D
H
Ph
H
7
H
6
Ph
Ph
Ph
Ph
Ph
Mn(CO)3
Ph
Mn
Mn
Ph
Mn
6
β-D-4b
5
Scheme 3. Metal-mediated phenyl-migration mechanism (note here and elsewhere, other ligand coordinations to Mn are omitted for clarity).
Mn
Ph
Ph
Ph
Ph
Ph
O
Ph
Mn(CO)3
H
O
O
O
D
H
α
H
H
H
β
D
Mn
D
Ph
7
6
D
Ph
Ph
H
Mn
Ph
Ph
Ph
β-D-4c
9
8
Scheme 4. Carbonyl addition–elimination ring-expansion mechanism.

W.J. Mace et al. / Journal of Organometallic Chemistry 690 (2005) 3340–3347
3343
O
D
_
O
O
H
H
H
Mn
Mn
+
D
7
Mn
Ph
Ph
10
11
7-D-3a (endo)
Ph
D
Scheme 5. Carbonyl addition–elimination ring-expansion mechanism with zwitterion intermediate (some substituents excluded for clarity).
quired and this would result in the movement of the me-
tal to the face opposite Ph giving the exo isomer as
shown (Scheme 4) rather than the observed endo prod-
uct. The mechanism of Scheme 3 was therefore preferred
[2b].
coordination of CH to Mn, the driving force for attain-
ment of the high degree (g5) of product stabilization
through metal coordination, is already well developed
in the acyl substitution transition state. The resulting
endo stereochemistry may reflect this demand.
Now, however, the finding that the D label finishes up
in the 7-position of the deuteriated form of 3a leads to
rejection of Scheme 3 and acceptance of the basic skele-
tal change, though not the stereochemistry, of Scheme 4.
The endo stereochemistry would require (Scheme 5) a
zwitterionic alkoxide intermediate 11 in place of 9,
whose instability in the non-polar medium could be off-
set if Mn were to provide better stabilization through
retention in a p-bonding mode (not shown in full in
Scheme 5) on the bottom face, where it would be ideally
positioned to attract the electron pair from the cyclopro-
pyl r-bond in the final forward ring-opening to the sta-
ble conjugated 1,2,3,4,5-g complex.
2.3. Structure of pyranyl complex 2a
The structure of the pyranyl complex 2a (see Fig. 1)
consists of a Mn(CO)3 ‘‘piano stool’’ moiety coordinat-
ing to a 2,4,6-substituted g5-pyranyl ring. The five car-
bon atoms C(1)–C(5) are essentially co-planar, with
the oxygen atom displaced such that the dihedral angle
between the C(1)–O(1)–C(5) plane and the g5-plane is
42.9(2)ꢁ.
The manganese atom is coordinated to the ring in an
unsymmetrical manner, with the Mn–C(5) distance of
˚
2.401(3) A significantly longer than the other Mn–C
˚
The instability of a bare alkoxide intermediate (11) in
the non-polar aprotic solvent would be circumvented in
a modified mechanism (Scheme 6) in which the rear-
rangement takes place by concerted acyl substitution
at the carbonyl carbon rather than through the two-step
addition–elimination sequence, with minimal negative
charge transfer onto the carbonyl oxygen. Nucleophilic
acyl substitution in esters by a concerted rather than
two-step addition–elimination mechanism is well-
established [4] if not common. Here, the substitution
reaction is at a ketone carbonyl, a reaction known in
organic chemistry only if the nucleophile is very strong
like amide or alkoxide [5a] or if the leaving group is sta-
bilized as a carbanion (e.g., as in b-diketones and triha-
lomethyl ketones [5b]). Perhaps in the acyl substitution
transition state 12, the CH leaving group may be stabi-
lized as in a b-diketone through conjugation around the
ring dienone system, but a key factor could be that the
bonds (2.127–2.189(3) A). We note that in the only other
reported g5-pyranyl-manganese structure of this type,
with 2,4-diphenyl-6-methyl substitution pattern, the
equivalent asymmetry was also found [2a], though to a
lesser extent. Whether this is a steric or electronic effect,
or even a general one, cannot be concluded on the basis
of these two examples.
The bond lengths around the ring system are not
equal, with C(3)–C(4) being the longest, and C(4)–C(5)
the shortest. The lengths do not correspond to a partic-
ular resonance form as the bonds do not give an alter-
nating pattern. The oxygen atom in the pyranyl ring
H
H
H
H
2
α
α
Ph
Ph
Ph
Ph
1
PhCH2Mn(CO)5
β
β
D
D
Mn
O
O
D
(CO)4
13
β-D-1a
O
PhC
CH
Ph
H
H
C
6
7-D-3a (endo)
O
D
H
Mn
1
Ph
7
H
Ph
Ph
12
Mn(CO)3
D
Scheme 6. Concerted acyl substitution ring-expansion mechanism
avoiding zwitterion intermediate (some substituents excluded for
clarity).
7-D-3a (endo)
Scheme 7. Deuterium labeling study.

3344
W.J. Mace et al. / Journal of Organometallic Chemistry 690 (2005) 3340–3347
Fig. 1. The molecular structure of [2,4-diphenyl-6-(2-phenylethenyl)pyranyl-g5]tricarbonylmanganese (2a).
has a shorter bond to C(5) compared to C(1), presum-
ably related to the unsymmetrical placing of the manga-
nese. The phenyl groups are not co-planar with the
pyranyl ring, being at angles of 36ꢁ and 26ꢁ to the g5-
plane, which limits any extended p–electron interaction.
Though the ethenyl group [C(6)–C(7)–C(31)] forms a
smaller angle (14ꢁ) there is no evidence for delocalisation
NMR spectra (CDCl3 as solvent) were recorded on
Bruker Avance DRX 300 or 400 instruments; extensive
signal overlaps with the large numbers of aryl hydrogen
and carbon atoms prevent complete individual signal
assignment in some cases.
3.2. Synthetic
˚
as the bond length of 1.334(5) A for C(6)–C(7) corre-
sponds to an unperturbed C@C double bond.
Reagents, solvents and purification methods are de-
scribed largely in the previous paper [2b]. Petroleum
spirit was the fraction of b.p. 60–80 ꢁC.
2.4. Summary
Preparations of cyclomanganated dienones 1a and 1b
have been described [2b] and their coupling reactions
with alkynes (typically 0.2 mmol 1 and 0.6 mmol alkyne
in 10 mL solvent) have been carried out as earlier under
nitrogen [2b]. Solvent and reaction duration are indi-
cated below in individual cases; reaction temperatures
other than room temperature (20–25 ꢁC) were either
controlled with an oil bath, or as the boiling point of sol-
vent for reactions under reflux (76 ꢁC in CCl4, 98 ꢁC in
heptane). Reactions were monitored by IR spectroscopy
and were sometimes interrupted before completion to
obtain pyranyl complexes, or for long sluggish reactions,
to limit decomposition. Yields stated should be consid-
ered in this context.
The synthetic and spectral monitoring work in this
and the previous paper [2b] shows the generality of the
reaction of alkynes with cyclomanganated dienones ini-
tially to form pyranyl complexes but accompanied by a
slower rearrangement to oxocycloheptadienyl com-
plexes. The deuterium labeling study supports a rear-
rangement mechanism in which the pyranyl complex
reverts to its ring-opened precursor (4a) which then,
through the alternative metal coordination mode (4c),
cyclises to a 6-membered ring system which rearranges
with ring expansion through a 3-membered ring car-
bonyl addition intermediate (10 ! 11 ! 3; Scheme 5)
or acyl substitution transition state (12 ! 3; Scheme 6)
to give the endo-oxocycloheptadienyl complex.
Pyranyl complexes 2 were normally recrystallised
from dichloromethane/petroleum spirit mixtures by
cooling to ꢀ20 ꢁC, and oxocycloheptadienyl complexes
3 from ethyl acetate/petroleum spirit by vapour diffusion.
3. Experimental
3.1. Spectral
3.2.1. [2,4-Diphenyl-6-(2-phenylethenyl)pyranyl-g5]
tricarbonylmanganese (2a)
Infrared spectra (dichloromethane) were recorded on
a Digilab FTS-45 FTIR spectrometer. Electrospray
mass spectra were recorded on a Fisons Instruments
VG Platform II instrument with samples prepared in a
dilute sodium methoxide solution in methanol to aid
ionisation ([M + MeO]ꢀ parent ions) for negative ion
mode operation [6].
[1-Phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-jO]ethenyl-
jC1]tetracarbonylmanganese 1a with phenylacetylene in
carbon tetrachloride at room temperature over 28 h
yielded 2a, separated on an alumina column using 1:8
v/v dichloromethane/petroleum spirit, and crystallised
as dark red needles (27%). Anal. Found: C, 70.94; H,
4.10. C28H19O4Mn Calc.: C, 70.89; H, 4.04%. IR:

W.J. Mace et al. / Journal of Organometallic Chemistry 690 (2005) 3340–3347
3345
m(CO) 2015 (vs), 1956 (s), 1934 (s) cmꢀ1. ESMS (MeOH,
NaOMe; ꢀ20 V) m/z 505 (100%; [M + MeO]ꢀ). 1H
NMR: d 7.91 (2H, d, 1H, J = 7.6 Hz, ArH), 7.56–7.31
(13H, m, Ar–H), 7.11 (1H, d, J = 15.6 Hz, H20), 6.32
(1H, d, J = 15.6 Hz, H10), 5.72 (1H, s, H3), 5.06 (1H,
s, H5). 13C NMR: d 222.2 (s, metal carbonyl),
137.1(s), 136.5 (s), 136.5 (s), 130.0 (d, C20), 129.6 (d),
129.2 (d), 129.0 (d), 128.7 (d), 128.4 (d), 127.4 (d),
127.0 (d), 123.8 (d, C10), 123.4 (d), 101.1 (s, C2), 97.2
(s, C4), 94.6 (s, C6), 82.4 (d, C3), 81.2 (d, C5).
106.4 (s, C2), 99.1 (d, C3), 76.3 (d, C5), 67.6 (d,
C1), 48.6 (d, C7), ꢀ1.2 (SiC).
3.2.4. [6-Oxo-2,3,4,7-tetraphenylcyclohepta-1,4-dienyl-
1,2,3,4,5-g]tricarbonylmanganese (3c)
[1-Phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-jO]ethenyl-
jC1]tetracarbonylmanganese (1a) was reacted with
diphenylacetylene in heptane at 30 ꢁC over 96 h during
which period only minor peaks corresponding to 2c
(2017, 1957, 1934 cmꢀ1) were observed as 1a disappeared
and 3c accumulated. Chromatography on an alumina
column (1:3 v/v ether/petroleum spirit as eluent) yielded
as a yellow-orange band only 3c (30%), again assumed
to be the endo isomer by analogy with 3a. IR: m(CO)
2028 (vs), 1969 (s), 1948 (s) cmꢀ1. ESMS (MeOH,
NaOMe; ꢀ20 V) m/z 581 (10%; [M + MeO]ꢀ), 549
(100%, [M ꢀ H]ꢀ). 1H NMR: d 7.51–6.83 (20H, m,
Ar–H), 4.67 (1H, m, H5), 3.92 (1H, m, H1), 2.82 (1H,
d, J = 3.6 Hz, H7). 13C NMR: d 220.8 (s, metal car-
bonyl), 191.4 (C6), 141.2 (s), 140.7 (s), 138.1 (s), 137.1
(s), 132.4 (d), 131.2 (d), 130.1 (d), 129.9 (d), 129.3 (d),
128.7 (d), 128.2 (d), 128.1 (d), 128.0 (d), 127.9 (d),
127.6 (d), 127.1 (d), 121.9 (s, C4), 116.4 (s, C2), 114.7
(s, C3), 79.7 (d, C5), 63.8 (d, C1), 47.3 (d, C7).
3.2.2. [2,3-Diphenyl-4-(2-trifluoromethylphenyl)-6-(2-
(trifluoromethylphenyl)ethenyl)pyranyl-g5]
tricarbonylmanganese (2f)
[1-(2-Trifluoromethylphenyl)-2-[(E)-3-(2-trifluorom-
ethylphenyl)prop-2-en-1-oyl-jO]ethenyl-jC1]tetracarbo-
nylmanganese (1b) with diphenylacetylene in heptane at
30 ꢁC over 48 h and chromatography on a silica layer
(1:3 v/v ethyl acetate/petroleum spirit as eluent) yielded
apart from some unreacted starting material the previ-
ously characterized [2b] 3f (9%) as well as the new pyr-
anyl complex 2f as a yellow oil (13%), characterized by
spectral properties only. IR: m(CO) 2020 (vs), 1962 (s),
1935 (s) cmꢀ1. ESMS (MeOH, NaOMe; ꢀ20 V) m/z
717 (100%; [M + MeO]ꢀ), 685 (50%, [M ꢀ H]ꢀ). 1H
NMR: d 8.22 (1H, d, J = 7.6 Hz, H3000), 7.72 (3H, m,
H3000, H600, H6000), 7.67 (1H, t, J = 7.7 Hz, H5000), 7.56
and 7.54 (each 1H, t, J = 8 Hz, H500, H4000), 7.43 (1H,
t, J = 7.5 Hz, H400), 7.2-7.0 (11H, m, H20, 2 · C6H5),
6.29 (1H, d, J = 15.4 Hz, H10), 4.93 (1H, s, H5). 13C
NMR: d 220.6 (s, metal carbonyl), 138.9 (d, C6000),
136.7 (s), 133–126 (multiple overlapping signals includ-
ing 132.9, 132.8, 132.2, 132.0, 129.4, 128.8, 128.5,
128.3, 127.9, 127.7, 127.4, 127.1, 126.7, 126.4, 126.0; aryl
and alkenyl CH), 104.7 (s, C2), 104.2 (s, C6), 102.9 (s,
C4), 84.4 (s, C3), 82.1 (d, C5).
3.2.5. [6-Oxo-2-phenyl-4,7-di(2-trifluoromethylphenyl)
cyclohepta-1,4-dienyl-1,2, 3,4,5-g]tricarbonylmanganese
(3d)
[1-(2-Trifluoromethylphenyl)-2-[(E)-3-(2-trifluorom-
ethylphenyl)prop-2-en-1-oyl-jO]ethenyl-jC1]tetracarbo-
nylmanganese (1b) was reacted with phenylacetylene in
heptane under reflux over 24 h. Chromatography on a
silica layer (1:3 v/v ether/petroleum spirit as eluent) gave
two bands from which were obtained the known [2b]
pyranyl complex 2d (17%) identified by IR [2014 (vs),
1934 (s, br) cmꢀ1] and the new, presumably endo, oxocy-
cloheptadienyl complex 3d (52%). Anal. Found: C,
59.25; H, 2.65. C30H17O4Mn Calc.: C, 59.03; H,
3.2.3. [6-Oxo-4,7-diphenyl-2-trimethylsilylcyclohepta-
1,4-dienyl-1,2,3,4,5-g]tricarbonylmanganese (3b)
2.81%. IR: m(CO) 2033 (vs), 1973 (s), 1960 (s) cmꢀ1
.
[1-Phenyl-2-[(E)-3-phenylprop-2-en-1-oyl-jO]ethenyl-
jC1]tetracarbonylmanganese 1a with (trimethylsi-
lyl)acetylene under reflux in heptane over 24 h and
chromatography on a silica layer (2:3 v/v ethyl ace-
tate/petroleum spirit as eluent) yielded equal amounts
of the previously characterized [2b] 2b (29%) and the
new oxocycloheptadienyl complex 3b, assumed to be
the endo isomer, as a yellow oil (29%), characterized
by spectral properties only. IR: m(CO) 2031 (vs),
1974 (s), 1947 (s) cmꢀ1. ESMS (MeOH, NaOMe;
ꢀ20V) m/z 469 (79%, [M-H]ꢀ), 397 (100%,
[M ꢀ SiMe3]ꢀ). 1H NMR: d 7.61–7.14 (10H, m, Ar–
H), 6.01 (1H, m, H3), 4.83 (1H, m, H5), 3.44 (1H,
m, H1), 2.52 (1H, d, J = 3.4 Hz, H7), 0.39 (9H, s,
SiCH3). 13C NMR: d 220.5 (s, metal carbonyl), 188.5
(C6), 140.8 (s), 138.2 (s), 130.4 (d), 129.8 (d), 129.2
(d), 129.2 (d), 129.1 (d), 127.7 (d), 122.7 (d, C4),
ESMS (MeOH, NaOMe; ꢀ20 V) m/z 641 (100%;
[M + MeO]ꢀ), 609 (10%, [M ꢀ H]ꢀ). 1H NMR: d
7.85–7.41 (13H, m, Ar–H), 6.40 (1H, m, H3), 4.61
(1H, m, H5), 4.04 (1H, m, H1), 2.94 (1H, d, J = 2.9
Hz, H7). 13C NMR: d 219.7 (s, metal carbonyl), 187.8
(C6), 138.9–125.5 (overlapping aryl and CF3 signals),
120.9 (d, C4), 112.0 (s, C2), 97.8 (d, C3), 77.0 (d, C5),
61.0 (d, C1), 41.8 (d, C7).
3.2.6. [6-Oxo-2-trimethylsilyl-4,7-di(2-trifluoromethyl-
phenyl)cyclohepta-1,4-dienyl-1,2,3,4,5-g]tricarbonyl-
manganese (3e)
[1-(2-Trifluoromethylphenyl)-2-[(E)-3-(2-trifluorom-
ethylphenyl)prop-2-en-1-oyl-j O]ethenyl-jC1]tetracar-
bonylmanganese (1b) was reacted with (trimethylsilyl)
acetylene in heptane under reflux over 7 days. Chroma-
tography on a silica layer (1:1 v/v dichloromethane/

3346
W.J. Mace et al. / Journal of Organometallic Chemistry 690 (2005) 3340–3347
Table 1
Selected bond parameters for [2,4-diphenyl-6-(2-phenylethenyl)pyra-
petroleum spirit as eluent) gave two bands from which
were obtained the known [2b] pyranyl complex 2e
(36%) identified by IR [2017 (vs), 1958(s), 1936 (s)
cmꢀ1] and ESMS [637 (32%, [M + MeO]ꢀ)], and the
new presumably endo oxocycloheptadienyl complex
3e, a yellow oil (20%) crystallised by vapour diffusion
(ethyl acetate/petroleum spirit): Anal. Found: C,
53.78; H, 3.41. C30H17O4Mn Calc.: C, 53.47; H,
nyl-g5]tricarbonylmanganese (2a)
˚
Bond lengths (A)
Mn(1)–C(1)
Mn(1)–C(3)
Mn(1)–C(5)
C(1)–O(1)
C(1)–C(2)
C(3)–C(4)
C(5)–C(6)
2.189(3)
2.131(3)
2.401(3)
1.428(3)
1.408(4)
1.438(3)
1.454(4)
Mn(1)–C(2)
Mn(1)–C(4)
Mn–CO (av.)
C(5)–O(1)
C(2)–C(3)
2.127(3)
2.177(3)
1.812(3)
1.387(3)
1.416(4)
1.392(4)
1.334(4)
3.49%. IR: m(CO) 2030 (vs), 1972 (s), 1949 (s) cmꢀ1
.
C(4)–C(5)
C(6)–C(7)
ESMS (MeOH, NaOMe; ꢀ20 V) m/z 565 (100%;
[M ꢀ SiMe3 + H + MeO]ꢀ), 533 (28%, [M ꢀ SiMe3]ꢀ).
1H NMR: d 7.79–7.41 (8H, m, Ar–H), 5.75 (1H, m,
H3), 4.68 (1H, m, H5), 3.50 (1H, m, H1), 2.88 (1H,
d, J = 2.9 Hz, H7), 0.35 (9H, s, SiCH3). 13C NMR: d
219.7 (s, metal carbonyl), 184.8 (C6), 138.8 (s), 136.4
(s), 132.6 (d), 132.4 (d), 131.0 (d), 129.6 (d), 127.2
Bond angles (ꢁ)
O(1)–C(1)–C(2)
C(2)–C(3)–C(4)
C(4)–C(5)–O(1)
117.5(3)
114.3(3)
119.2(3)
C(1)–C(2)–C(3)
C(3)–C(4)–C(5)
C(1)–O(1)–C(5)
118.5(3)
121.2(3)
107.1(2)
After solvent removal the residue was chromatographed
on an alumina column using 1:1 v/v dichloromethane/
petroleum spirit as eluent. The orange-yellow band
provided (Scheme 7) endo-[6-oxo-2,4,7-triphenylcyclo-
hepta-1,4-dienyl-7-d-1,2,3,4,5-g]tricarbonylmanganese
(7-D-3a, 22 mg, 10%): d 2.64 (trace of signal only, resid-
ual H7), 3.97 (IH, m, H1), 4.80 (1H, m, H5), 6.64 (1H,
m, H3), 7.3–7.8 (15H, Ar–H).
1
(d), 126.9 (q, JCF = 5.3 Hz, CF3), 125.8 (d,
1
2JCF = 13.3 Hz, C-CF3), 125.4 (q, JCF = 5.6 Hz,
2
CF3), 124.1 (C4), 122.2 (d, JCF = 13.3 Hz, C–CF3),
104.1 (C2), 102.0 (C3), 77.3 (C5), 70.7 (C1), 43.2
(C7), ꢀ1.6 (SiCH3).
3.3. Deuterium-labeling study (Scheme 7)
3.4. Structure of [2,4-diphenyl-6-(2-phenylethenyl)
pyranyl-g5]tricarbonylmanganese (2a)
Ethanol (10 mL) and a solution of sodium hydroxide
(2 g) in water (15 mL) were mixed in a flask immersed in
crushed ice. A mixture of acetone (ca. 0.36 mL; 4.9
mmol) and benzaldehyde-formyl-d (Aldrich 98 at.%;
1.0 mL, 9.8 mmol) was added dropwise with stirring
over 10 min. After a further 1 h without cooling, the pre-
cipitate was collected under vacuum in a sintered glass
funnel and washed with water until the washings were
neutral to litmus. The crude product was dried under
vacuum and recrystallized from ethyl acetate to give
1,5-diphenylpenta-1,4-dien-3-one-1,5-d2 as pale lemon
needles (13; 0.84 g; 73%). 1H NMR spectral data
matched those [2b] of 1a except for the absence of the
b-proton signal at d 7.75, and with the a-proton signal
(d 7.10) now a broad singlet.
This compound (13; 500 mg, 2.1 mmol) and benzyl-
pentacarbonylmanganese (660 mg, 2.3 mmol) were re-
acted to completion under reflux over 5 h in petroleum
spirit (b.p. 60–80 ꢁC) in a nitrogen atmosphere (Schlenk
flask). The solvent was removed and the product chro-
matographed on an alumina column using 1:8 v/v
dichloromethane/petroleum spirit as eluent. The prod-
2a was characterised by single-crystal X-ray crystal-
lography. Accurate cell parameters and intensity data
were collected by x-scans on a Siemens SMART diffrac-
˚
tometer with Mo Ka radiation (k = 0.7107 A) at ꢀ105
ꢁC. The structure was solved by Direct Methods and
routinely developed. Refinement was full-matrix least-
squares based on F2, using the SHELX programs [7] run-
ning under the WinGX suite of programmes [8].
Crystal data: C28H19MnO4, M 474.37, monoclinic,
˚
P21/c, a 14.165(4), b 12.397(4), c 13.581(4) A, b
3
109.91(1)ꢁ, U 2242.3 A , Dc 1.405 g cmꢀ3 for Z 4,
˚
F(000) 976, l(Mo Ka) 0.621 mmꢀ1. Red prismatic crys-
tals from CH2Cl2, 0.68 · 0.44 · 0.15 mm3. A total of
28,026 reflections with 2ꢁ < 2h < 50ꢁ were collected,
4552 unique (Rint 0.0332), 3772 with I > 2r(I), corrected
for absorption (Tmax, min 1.000, 0.863). All non-H atoms
anisotropic, H atoms in calculated positions. Refine-
ment converged with R1 0.0464 (2r data), wR2 0.1305
(all data), GoF 1.137, largest residual feature 1.0
e Aꢀ3. The structure is illustrated in the Fig. 1, and
˚
uct
[[1-phenyl-2-(E)-3-phenylprop-2-en-1-oyl-3-d-jO]
the Table 1 lists selected bond parameters.
ethenyl-jC1]tetracarbonylmanganese (b-D-1a) was ob-
tained as the main fraction (390 mg, 46%). NMR data
matched those of the protio analogue 1a except for the
absence of the b-proton signal (d 7.72 in 1a [2b]) and
the now broad singlet signal from the adjacent a-proton
(d 6.99); the other singlet a-proton signal (d 7.33; H2
using the numbering in Scheme 7) was retained.
4. Supplementary material
Full details of the structure determination have been
deposited with the Cambridge Crystallographic Data
Centre as CCDC 263330. Copies of this information
may be obtained free of charge from The Director,
CCDC, 12 Union Road, Cambridge CB2 1EZ, UK
b-D-1a (184 mg, 0.46 mmol) and PhCCH (180 lL,
1.64 mmol) were heated in CCl4 under reflux for 24 h.

W.J. Mace et al. / Journal of Organometallic Chemistry 690 (2005) 3340–3347
3347
(b) W. Tully, L. Main, B.K. Nicholson, J. Organomet. Chem. 633
(2001) 162–172.
(fax: +44 1223 336 033; e-mail: deposit@ccdc.cam.ac.uk
or www: http//www.ccdc.cam.ac.uk).
[3] C-W. Lee, K.S. Oh, K.S. Kim, K.H. Ahn, Org. Lett. 2 (2000)
1213.
[4] A. Williams, Acct. Chem. Res. 22 (1989) 387–392.
[5] (a) J. March, Advanced organic chemistry, third ed., Wiley, New
York, 1985, pp. 567–568;
Acknowledgements
(b) J. March, Advanced Organic Chemistry, third ed., Wiley, New
York, 1985, pp. 566–567.
We thank Dr. J. Wikaira, University of Canterbury,
for collection of X-ray intensity data.
[6] W. Henderson, J.S. McIndoe, B.K. Nicholson, P.J. Dyson, J.
Chem. Soc., Dalton Trans. (1998) 519.
[7] (a) G.M. Sheldrick, SHELXS-97, University of Gottingen, Gottingen,
Germany, 1997;
References
(b) G.M. Sheldrick, SHELXL-97, University of Gottingen, Gottingen,
Germany, 1997.
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[8] L.J. Farrugia, WinGX, Version 1.64.05, University of Glasgow,
UK;
L.J. Farrugia, J. Appl. Cryst. 32 (1999) 837.