Reactions of molybdenum tetrahydrido complex with halohydrosilanes

Article abstract of DOI:10.1246/bcsj.20090211

The thermal reactions of [MoH₄(dppe)₂](1, dppe = Ph₂PCH₂CH₂PPh₂)with RSiH ₂Xafford [MoH₂X(dppe)-{[Ph₂PCH ₂CH₂P(Ph)C₆H₄-o]RXSi-P,P,Si}](R = Ph, X = Cl (5a); R = cycfo-C₆H₁₁, X = Cl (5b); and R = Ph, X = Br (6)) by activation of the Si-H bond of the silanes and the ortho C-H bond of the phenyl group in the dppe ligand. Reduction of the Si-Cl and Mo-Cl bonds in 5a with LiAlH₄ leads to the formation of the original complex 1 as a result of unusual Si-C bond cleavage. Meanwhile, dehalogenative reduction of 5a using zinc metal gives the known compound [MoH ₃{[Ph₂PCH₂CH₂P(Ph)C ₆H₄-o]₂(Ph)Si-P,P,P,P,Si}](2). The experimental results reported herein provide certain evidence for the involvement of the silylene species in the unusualformation of the present polydentate phosphinoalkyl-silylligands.

Full text of DOI:10.1246/bcsj.20090211

© 2010 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 83, No. 2, 165–169 (2010)
165
Reactions of Molybdenum Tetrahydrido Complex with Halohydrosilanes
Satoru Kuramochi,1 Yo-hei Kido,1 Syunsuke Shioda,1 Makoto Minato,*1
Masaki Kakeya,2 and Kohtaro Osakada2
1Department of Materials Chemistry, Graduate School of Engineering, Yokohama National University,
79-5 Tokiwadai, Hodogaya-ku, Yokohama 240-8501
2Research Laboratory of Resources Utilization, Tokyo Institute of Technology,
4259 Nagatsuta, Midori-ku, Yokohama 226-8503
Received August 12, 2009; E-mail: minato@ynu.ac.jp
The thermal reactions of [MoH4(dppe)2] (1, dppe = Ph2PCH2CH2PPh2) with RSiH2X afford [MoH2X(dppe)-
{[Ph2PCH2CH2P(Ph)C6H4-o]RXSi-P,P,Si}] (R = Ph, X = Cl (5a); R = cyclo-C6H11, X = Cl (5b); and R = Ph, X = Br
(6)) by activation of the Si-H bond of the silanes and the ortho C-H bond of the phenyl group in the dppe ligand.
Reduction of the Si-Cl and Mo-Cl bonds in 5a with LiAlH4 leads to the formation of the original complex 1 as a result of
unusual Si-C bond cleavage. Meanwhile, dehalogenative reduction of 5a using zinc metal gives the known compound
[MoH3{[Ph2PCH2CH2P(Ph)C6H4-o]2(Ph)Si-P,P,P,P,Si}] (2). The experimental results reported herein provide certain
evidence for the involvement of the silylene species in the unusual formation of the present polydentate phosphinoalkyl-
silyl ligands.
Transition-metal silyl complexes constitute
a
widely
We have also demonstrated the high reactivity of the
resulting complexes 2 and 3 toward various substances. To
date, we have prepared and structurally characterized a number
of new related compounds having these novel polydentate
phosphinoalkyl-silyl ligands.3
We are particularly interested in exploring how variation of
the substituents on the silane affects the formation of the
products. Reported here are the results of studies extending
this chemistry to halohydrosilanes. It has been established
that activation of Si-H bonds in halohydrosilanes would be
preferable to that of the Si-X (X = halogen) bond.1a However,
there have been several reports of facile activation of the Si-X
bonds.4 Thus, it is a moot point whether an oxidative addition
of Si-H bond would take place or whether a Si-X bond
cleavage would proceed.
studied class of organometallic compounds.1 Recently, we
have reported that the thermal reaction of [MoH4(dppe)2] (1,
dppe = Ph2PCH2CH2PPh2) with phenylsilane leads not only to
oxidative addition of a Si-H bond to the metal center but also
to activation of the ortho C-H bonds of the phenyl groups in
the two dppe ligands to give a new class of molybdenum-silyl
hydrido complex 2 with a novel pentadentate ligand comprised
of a P-P-Si-P-P framework (Scheme 1).2 We have found that
this reaction is not limited to primary silanes. Even in the case
of a secondary silane system, similar activation of the Si-H
bond and the ortho C-H bond took place to give a hydrido
complex 3 with a tridentate ligand comprised of a P-P-Si
framework.
The most plausible pathway for these novel transformations
seemed to involve orthometallation by dppe of 16-electron
[MoH2(dppe)2] formed by H2 loss, followed by oxidative
addition of the silanes.2c However, significant insight into the
mechanism of this unusual C-Si bond formation was obtained
by investigation using deuterium-labeling, which suggests that
the reaction path includes the intermediacy of a silylene metal
complex via an ¡-migration of hydrogen as is mentioned in the
latter part.2d
Results and Discussion
Reaction of [MoH4(dppe)2] with Halohydrosilanes. The
reactions of 1 with 2 equiv of RSiH2X (R = Ph, cyclo-C6H11;
X = Cl, Br) in toluene at ambient temperature afforded the
known cis-[MoH2X2(dppe)2] (4a, X = Cl; 4b, X = Br)5 in
moderate yields (ca. 50%). It is well-known that in the presence
of halocarbons transition-metal hydrido complexes occasion-
Ph
Ph
Ph
Ph
Ph
Ph
H2C
H Si
H Si
Ph
Ph
PhSiH3
Ph2SiH2
P
P
P
P
H2C
H2C
Ph
CH2
CH2
Ph
CH2
[MoH4(dppe)2]
Mo
Mo
H2C
Ph
CH2
Ph
P
P
P
P
1
H H
H
H
Ph
Ph
Ph
Ph
2
3
Scheme 1.
Published on the web January 29, 2010; doi:10.1246/bcsj.20090211

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Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
Reactions of Mo Complex with RSiXH2
Ph
Ph
Ph
X
X
Ph
P
P
r. t.
H2C
CH2
Mo
CH2
Ph
H2C
Ph
P
P
H
H
Ph
Ph
4a: X = Cl
4b: X = Br
2 RSiXH2
1
R
X
Ph
Ph
H Si
Ph
P
P
110 °C
H2C
H2C
Ph
CH2
Mo
P
CH2
Ph
P
X
H
Ph
Ph
5a: R = Ph, X = Cl
5b: R = cyclo-C6H11, X = Cl
6 : R = Ph, X = Br
Figure 1. ORTEP drawing of 5a.
Table 1. Selected Interatomic Distances and Angles in 5a
Distances/¡
Scheme 2.
Mo1-Cl1
Mo1-P2
Mo1-P4
Cl2-Si1
Si1-C8
2.5421(8)
2.5379(1)
2.5263(1)
2.159(2)
1.894(3)
Mo1-P1
Mo1-P3
Mo1-Si1
Si1-C1
2.4762(9)
2.4819(1)
2.4744(1)
1.904(3)
ally undergo metathesis to give the corresponding halogeno
1
compounds.6 Indeed, H NMR study revealed that the reaction
between 1 and CCl4 produced 4a in a similar manner. Thus, in
the case of RSiH2X, the analogous conversion appeared to take
place.
The increase of reaction temperature altered the reaction
dramatically. At 110 °C, dihydrido complexes (R = Ph, X = Cl
(5a); R = cyclo-C6H11, X = Cl (5b); and R = Ph, X = Br (6))
with a tridentate ligand ([Ph2PCH2CH2P(Ph)C6H4-o]RXSi-
P,P,Si) comprised of the P-P-Si framework were isolated,
according to Scheme 2. As expected, the activation of the Si-H
bond in the halohydrosilanes and the ortho C-H bond of the
phenyl group in the dppe ligand occurred. We have also
confirmed that reaction of 4a with PhSiH2Cl at 110 °C does not
give 5a. Consequently, the first step is the thermally induced
formation of 16-electron [MoH2(dppe)2]. These results dem-
onstrate that complex 1 displays a pronounced preference for
Si-H oxidative addition over Si-X oxidative addition at
elevated temperatures. In addition, just as in the foregoing
reactions of the secondary silanes, the process would include
the intermediacy of a silylene metal complex via ¡-migration
of hydrogen. Probably the resulting trihydrido complexes
further react with the halohydrosilanes to produce the halogeno
dihydrido compounds 5 and 6.
Angles/°
Cl1-Mo1-Si1 150.62(4)
P1-Mo1-P2
P1-Mo1-P4 103.96(4)
P2-Mo1-P3
P3-Mo1-P4
P4-Mo1-Si1
76.93(3)
P1-Mo1-P3
P1-Mo1-Si1
P2-Mo1-Si1
P3-Mo1-Si1
Cl2-Si1-C8
164.05(3)
74.01(3)
100.25(3)
121.67(3)
97.92(2)
96.03(4)
79.10(3)
94.51(4)
and 6 show four multiplet resonances at around 84, 63, 59, and
45 ppm with a 1:1:1:1 peak area ratio. The results indicate the
presence of four nonequivalent P nuclei in each complex.
Figure 1 shows an ORTEP drawing of 5a. Some pertinent
bond distances and angles are collected in Table 1. The crystal
structure unambiguously indicates that the compound contains
a new bond between the silicon atom and the ortho carbon of
the phenyl group in one of the dppe ligands. Complex 5a
adopts a distorted, square antiprismatic geometry about the
molybdenum center; the four phosphorus atoms occupy the
equatorial coordination sites. Although the overall geometry of
5a is very similar to that observed for 3, the metric parameters
differ from one another (vide infra). The chloro ligand is
axially coordinated trans to the silyl group. The hydrido
ligands are not located. However their presence is confirmed
by means of 1H NMR and IR spectroscopy. A conspicuous
structural feature is that the Mo-Cl bond of 2.5421(8) ¡ in
5a is considerably longer than the value of 2.387 ¡ in 4a.5b
Consequently, the differing trans influence of the hydrido
versus silyl ligand is at least semiquantitatively observed.
Although both hydrido and silyl groups are known to have
good ·-donor ability which is closely concerned with the trans-
influence,8 our results have clearly verified that the silyl group
has a high trans-influence much greater than the hydrido ligand.
Complexes 5 and 6 have been characterized by IR, and
1H and 31P NMR spectroscopies as well as by a preliminary
X-ray crystal structure determinations (5a and 6).7 The NMR
spectroscopic data for 5 and 6 illustrate that two complexes
exhibit only slight differences in their chemical shifts and
coupling patterns; these results are consistent with the X-ray
analysis (vide infra).
The IR spectra of complexes 5 and 6 showed ¯(Mo-H) at
1716-1718 cm¹1, which are at lower frequency than that of 3
1
by about 10 cm¹1. The H NMR spectra of 5 and 6 consist of
broad peaks arising from PCH2CH2P protons between 2.2 and
2.6 ppm and of broad multiplet signals corresponding to two
hydrido protons at around ¹6 ppm, which are at higher field
compared with 2 and 3. The 31P{1H} spectra of complexes 5

S. Kuramochi et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
167
Ph
Ph
Ph
H SiH
Mo
Ph
P
Ph
Ph
Ph
Ph
H SiH
Ph
CH2
CH2
Ph
Ph
CH2
CH2
Ph
2 P
2 P
P
-H2
-H2
PhSiH3
1,2-H shift
H2C
H2C
H2C
H2C
Ph
[MoH2(dppe)2]
16e
[MoH4(dppe)2]
Mo
P
P
P
P
Ph
H
H
Ph
Ph
A
1
Ph
Ph
16e
B
Ph
H
Ph
Ph
Si
Ph
H Si
Ph
Ph
Ph
CH2
H
H
H
Ph
HSi
Ph
Ph
Ph
H
H
Ph
H2C
Si
Ph
CH2
Ph
CH2
Ph
P
P
P
P
P
P
P
P
-H2
H2C
H2C
Ph
H2C
H2C
Ph
H2C
H2C
Ph
CH2
Mo
Mo
Mo
Mo
CH2
Ph
H2C
CH2
Ph
CH2
Ph
CH2
Ph
P
P
P
P
P
P
P
P
Ph
H
H
H
H
H
Ph
Ph
Ph
Ph
Ph
Ph
Ph
Ph
C
D
2
E
Scheme 3.
The mean Mo-P bond distance at 2.5056 ¡ in 5a is
appreciably longer than that of 2.4645 ¡ in 3. In contrast
the Mo-Si bond length of 2.4744(1) ¡ in 5a is significantly
shorter than the value of 2.541(2) ¡ in 3. This distance is also
quite short when compared to the other Mo-Si distances of
structurally characterized complexes derived from 2 and 3,
which range from 2.518 to 2.559 ¡.3 Furthermore, the Si-Cl
length of 2.159(2) ¡ in 5a is considerably longer than the value
of 2.079 ¡ found in Ph3SiCl.9 These structural data for 5a may
be understood in terms of an interaction of the anti-bonding ·*-
orbital of silicon to chloride and the molybdenum d³ orbital.1a
As mentioned previously, on the basis of deuterium-label-
ing, we proposed that the reaction between 1 and phenylsilane
occurs by the sequence of events shown in Scheme 3.2d
The first step, the loss of H2 upon thermolysis of 1 is well
documented.10 The silane addition product A would undergo
further loss of H2 to give a putative 16-electron intermediate B
which rearranges to a hydrido(hydrosilylene) complex C via
an overall 1,2-H shift. Recently, this type of transformation
has been firmly established by Tobita et al. for group 6
transition-metal hydridos [Cp¤(CO)2(H)W=Si(H){C(SiMe3)3}]
(Cp¤ = Cp* or ©5-C5Me4Et).11 Strong interactions between the
silylene and hydrido ligands have been shown to exist in these
complexes, thus the driving force for the formation of C may
be a similar interligand interaction. The following ortho C-H
bond scission of a phenyl group in one of the dppe ligand
would produce the presumed intermediate D. A similar process
(activation of an intramolecular aromatic C-H bond by silylene
complexes) has been observed in ruthenium systems.12 Since
we could not detect the silylene intermediate C spectroscopi-
cally it is assumed that the lifetime of this species might be so
short that it would not exist in sufficient concentration to be
species E. Thus, further study of 5a was directed toward
understanding the reaction chemistry of the chloro substituents
on the silyl group and the molybdenum center with the goal of
obtaining the mechanistic insight.
Reduction of 5a with LiAlH4 and Zinc. First we carried
out reduction of 5a with LiAlH4 in THF at 67 °C (Scheme 4).
Surprisingly, the 1H NMR spectrum of the crude reaction
mixture indicated the major species present to be the original
complex 1 (40%). The reaction probably led first to reduction
of the Cl groups and then to the Si-Mo and Si-Ph bond
cleavage.
An activation of Si-C bonds is potentially important in the
development of new processes in organosilicon chemistry,
although cleavage of an Si-Ph bond has fewer precedents.13 It
is generally recognized that transition-metal silyl complexes
are susceptible to nucleophilic attack at silicon.1a In some silyl
complexes, LiAlH4 can displace the silyl group as the
corresponding silane by direct attack at silicon.14 However,
the cleavage of an alkyl-silicon bond has seldom been
observed in these reductions. The formation of 1 is thus highly
puzzling at present, and the mechanistic details will be clarified
by further work.
Next we explored the dehalogenation reaction of 5a. Stirring
5a in THF with an excess of zinc metal at reflux temperature
for 4 h resulted in the formation of a yellow-green solution,
from which the anticipated product 2 was isolated as the only
major product (27%).15 The formation of 2 can be rationalized
according to Scheme 5. Complex 5a would undergo a two-
electron reduction by Zn metal to form a dianionic species.
Subsequent elimination of two chloride anions would yield the
silylene species E which then inserts into the ortho C-H bond
of the phenyl group to give 2.
1
observable in a H NMR spectrum. We think that the present
Conclusion
insertion process is very rapid and is promoted by steric
acceleration due to easy access of the C-H bond to the active
site. The sequence of processes would repeat to attach Si to the
other dppe ligand affording the final product 2.
We have thought that complex 5a provides a direct approach
to verify the validity of the above assumptions. At first glance
the intermediate D would appear to be accessible through
reduction of 5a with a hydride reagent. Alternatively, dehalo-
genation of 5a would lead to the generation of the silylene
The reactions of [MoH4(dppe)2] (1) with RSiH2X were
investigated. At ambient condition the reactions afford the
known cis-[MoH2X2(dppe)2]; thus, facile activation of the Si-X
bonds takes place. On the other hand, the reactions in refluxing
toluene lead to the isolation of [MoH2X(dppe){[Ph2PCH2-
CH2P(Ph)C6H4-o]RXSi-P,P,Si}] (R = Ph, X = Cl (5a); R =
cyclo-C6H11, X = Cl (5b); and R = Ph, X = Br (6)) with the
tridentate phosphinoalkyl-silyl ligand. These reactions proceed

168
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
Reactions of Mo Complex with RSiXH2
Ph
H
Ph
Ph
Si
H
Ph
P
P
H2C
H2C
Ph
CH2
Mo
CH2
Ph
P
P
Ph
Cl
H
H
Ph
Ph
Ph
Ph
H Si
Ph
LiAlH4
D
P
P
H2C
CH2
CH2
Ph
Mo
H2C
Ph
P
P
Cl
H
Ph
Ph
5a
[MoH4(dppe)2]
1
Scheme 4.
2-
Ph
Cl
Ph
H Si
Zn
Zn2+
Ph
Ph
Ph
Ph
H
Si
Ph
Ph
-2 Cl
P
P
P
P
P
H2C
H2C
Ph
H2C
H2C
Ph
CH2
CH2
Ph
CH2
2
5a
Mo
Mo
CH2
Ph
P
P
P
H
H
Ph
Ph
Cl
Ph
Ph
E
Scheme 5.
to yield 0.27 g (81%) of 4a. The spectroscopic properties of 4a are
consistent with those of cis-[MoH2Cl2(dppe)2].5 Complex 4b was
prepared in a manner similar to that for 4a in 85% yield.
by a route entirely similar to those reported for complexes 2
and 3; that is, Si-H, C-H, Si-C, and H-H bond cleavage/
formation all occur in the same system. The existence in
the resulting complexes of halide substituents seems to make
them susceptible to further transformation. Reduction of 5a
with LiAlH4 unexpectedly leads to the formation of the parent
complex 1, which would involve an unusual activation of Si-C
bond. In contrast, dehalogenation of 5a using zinc metal gives
complex 2. The experimental results reported herein provide
certain evidence for the involvement of the silylene species in
the unusual formation of the present polydentate phosphi-
noalkyl-silyl ligands. Further studies on these and other related
reactions are in progress.
Reactions of 1 with PhSiH2Cl at 110 °C. A solution of 1
(0.28 g, 0.31 mmol) and PhSiH2Cl (90 ¯L, 0.63 mmol) in toluene
(30 mL) was heated with stirring at 110 °C for 3 h. The resulting
solution was concentrated to a volume of 25 mL under reduced
pressure. Hexane (3 mL) was then added, and the mixture was
allowed to stand for 12 h at 0 °C, whereupon yellow precipitates
separated. The product was collected by filtration, washed
with hexane (10 mL © 3), and then dried in vacuo to give 5a
1
(0.23 g, 69%). 5a: IR data (KBr): ¯(Mo-H) 1716 cm¹1. H NMR
(270 MHz, C6D6, ppm): 8.0-6.5 (m, aromatics), 2.6-2.2 (m,
PCH2), ¹5.80- ¹6.35 (br m, 2H, MoH). 31P NMR (C6D6, ppm):
83.0 (ddd, 1P, Jpp = 5, 21, 121 Hz), 63.0 (ddd, 1P, Jpp = 10, 21,
116 Hz), 62.0 (ddd, 1P, Jpp = 10, 27, 121 Hz), 43.0 (ddd, 1P,
Experimental
General Procedures. All manipulations were performed using
standard Schlenk techniques under purified argon. All reagents
were purchased from commercial suppliers and used as received
without further purification. All solvents were dried by standard
methods and were stored under argon. Complex 116 and RSiH2X17
were synthesized according to procedures previously reported. All
NMR spectra were recorded on a JEOL-JNM-270 spectrometer.
31P{1H} NMR peak positions were referenced to external PPh3.
Jpp = 5, 27, 116 Hz). Anal. Calcd for C58H54Cl2MoP4Si: C, 65.11;
H, 5.09%. Found: C, 64.33; H, 5.54%. Complex 5b was prepared
in a manner similar to that for 5a in 74% yield. 5b: IR data (KBr):
¹1
¯(Mo-H) 1718 cm
.
1H NMR (270 MHz, C6D6, ppm): 8.0-6.5
(m, aromatics), 2.6-2.2 (m, PCH2), 2.0-1.2 (m, 11H, C6H11),
¹5.80- ¹6.75 (br m, 2H, MoH). 31P NMR (C6D6, ppm): 85.0 (ddd,
1P, Jpp = 5, 22, 118 Hz), 61.0 (ddd, 1P, Jpp = 8, 22, 115 Hz), 57.0
(ddd, 1P, Jpp = 8, 27, 118 Hz), 46.0 (ddd, 1P, Jpp = 5, 27, 115 Hz).
Anal. Calcd for C58H60Cl2MoP4Si: C, 64.75; H, 5.62%. Found: C,
64.62; H, 5.96%.
Reactions of 1 with PhSiH2Br at 110 °C. PhSiH2Br (110 ¯L,
0.59 mmol) was added dropwise with stirring to a solution of 1
(0.27 g, 0.30 mmol) in toluene (30 mL) at 110 °C. After stirring for
3 h the resulting solution was concentrated to a volume of 25 mL
under reduced pressure. Hexane (2 mL) was then added, and the
mixture was allowed to stand for 12 h at 0 °C, whereupon yellow
precipitates separated. The product was collected by filtration,
Reactions of 1 with PhSiH2X at Ambient Temperature.
A
solution of 1 (0.31 g, 0.35 mmol) and PhSiH2Cl (100 ¯L, 0.75
mmol) in benzene (35 mL) was stirred overnight, during which
time the solution turned from yellow to orange. The reaction
mixture was then allowed to stand for 12 h at 0 °C, whereupon
precipitates of unreacted 1 separated. The supernatant solution was
removed with a bridge filter. The volatiles were removed in vacuo
and the residue thus obtained was washed with diethyl ether
(8 mL © 3). The resulting yellowish solid was dried under vacuum

S. Kuramochi et al.
Bull. Chem. Soc. Jpn. Vol. 83, No. 2 (2010)
169
washed with hexane (10 mL © 3), and then dried in vacuo to
Osakada, Chem. Lett. 1998, 187. c) G. J. Kubas, Metal Dihydrogen
and ·-Bond Complexes, Kluwer, New York, 2001, pp. 339-340.
d) M. Minato, D.-Y. Zhou, L.-B. Zhang, R. Hirabayashi, M.
Kakeya, T. Matsumoto, A. Harakawa, G. Kikutsuji, T. Ito,
Organometallics 2005, 24, 3434.
¹1
give 6 (0.28 g, 80%). 6: IR data (KBr): ¯(Mo-H) 1716 cm
.
1H NMR (270 MHz, C6D6, ppm): 8.0-6.5 (m, aromatics), 2.6-2.2
(m, PCH2), ¹6.25- ¹6.75 (br m, 2H, MoH). 31P NMR (C6D6,
ppm): 79.0 (ddd, 1P, Jpp = 5, 22, 116 Hz), 56.0 (ddd, 1P, Jpp = 12,
27, 116 Hz), 53.0 (ddd, 1P, Jpp = 12, 22, 112 Hz), 44.0 (ddd, 1P,
3
a) M. Minato, D.-Y. Zhou, K. Sumiura, R. Hirabayashi, Y.
J
pp = 5, 27, 112 Hz). At present, no sample suitable for combus-
Yamaguchi, T. Ito, Chem. Commun. 2001, 2654. b) T. Ito, K.
Shimada, T. Ono, M. Minato, Y. Yamaguchi, J. Organomet. Chem.
2000, 611, 308. c) M. Minato, J. Nishiuchi, M. Kakeya, T.
Matsumoto, Y. Yamaguchi, T. Ito, Dalton Trans. 2003, 483. d) M.
Minato, G. Kikutsuji, M. Kakeya, K. Osakada, M. Yamasaki,
Dalton Trans. 2009, 7684.
tion analysis is available.
Reduction of 5a with LiAlH4.
A slurry of 5a (0.15 g,
0.14 mmol) and LiAlH4 (0.029 g, 0.75 mmol) in THF (10 mL) was
prepared at 0 °C and warmed to ambient temperature. The slurry
was then allowed to reflux overnight. Subsequently the reaction
mixture was cooled to ambient temperature and slowly hydrolyzed
with water (1 mL), following which the solvent and volatiles were
removed under vacuum. The resulting solid was extracted with
benzene. After evaporation of the benzene, the residue was washed
with hexane (5 mL © 3) and dried under vacuum, yielding 0.05 g
(40%) of 1.
4
a) H. Yamashita, T. Hayashi, T.-a. Kobayashi, M. Tanaka,
M. Goto, J. Am. Chem. Soc. 1988, 110, 4417. b) H. Yamashita,
T.-a. Kobayashi, T. Hayashi, M. Tanaka, Chem. Lett. 1990, 1447.
c) A. A. Zlota, F. Frolow, D. Milstein, J. Chem. Soc., Chem.
Commun. 1989, 1826.
5
a) K. E. Oglieve, R. A. Henderson, J. Chem. Soc., Dalton
Reduction of 5a with Zinc. A slurry of 5a (0.16 g, 0.16 mmol)
and zinc powder (0.10 g, 1.6 mmol) in THF (15 mL) was allowed
to reflux for 4 h. After removal of ca. 10% of the solvent in vacuo,
hexane (5 mL) was added, and the mixture was allowed to stand
for 12 h at 0 °C. The resulting mixture was filtered, and the filtrate
was evaporated in vacuo. The residue was washed with hexane
(5 mL © 3) and dried under vacuum, yielding 0.04 g (27%) of 2.
X-ray Crystallographic Analysis of 5a. Single crystals of 5a
suitable for X-ray analysis were obtained by slow recrystallization
from toluene-hexane. The intensity data were collected on a
Rigaku Saturn CCD area detector with graphite monochromated
Mo K¡ radiation (- = 0.71070 ¡). The structure was solved by
direct methods (SIR200218) and expanded using Fourier tech-
niques (DIRDIF9919). Some non-hydrogen atoms were refined
anisotropically, while the rest were refined isotropically. Hydrogen
atoms were refined using the riding model. Crystal data for 5¢C7H8
at ¹160 °C: C65H60Cl2MoP4Si, MW = 1160.02, triclinic, space
Trans. 1991, 3295. b) E. B. Lobkovskii, V. D. Makhaev, A. P.
Borisov, K. N. Semenenko, M. Y. Antipin, Y. T. Struchkov, Koord.
Khim. 1985, 11, 983.
6
a) H. Werner, R. Weinand, W. Knaup, K. Peters, H. G. von
Schnering, Organometallics 1991, 10, 3967. b) T. S. Koloski,
D. C. Pestana, P. J. Carroll, D. H. Berry, Organometallics 1994, 13,
489.
7
We have confirmed that the molecular structure of 6 is
analogous to that of 5a. The crystallographic details of 6 will be
discussed elsewhere.
8
J. P. Collman, L. S. Hegedus, J. R. Norton, R. G. Finke,
Principles and Applications of Organotransition Metal Chemistry,
2nd ed., California University Science Books, Mill Valley, 1987,
p. 243.
9
E. B. Lobkovskii, V. N. Fokin, K. N. Semenenko, Zh.
Strukt. Khim. 1981, 22, 152.
10 a) F. Pennella, J. Chem. Soc. D 1971, 158a. b) M. Minato,
H. Sakai, Z.-G. Weng, D.-Y. Zhou, S. Kurishima, T. Ito, M.
Yamasaki, M. Shiro, M. Tanaka, K. Osakada, Organometallics
1996, 15, 4863.
11 T. Watanabe, H. Hashimoto, H. Tobita, Angew. Chem., Int.
Ed. 2004, 43, 218.
ꢀ
group P1 (#2), Z = 2, a = 12.7418(1) ¡, b = 13.4611(1) ¡, c =
20.5471(2) ¡, ¡ = 72.698(5)°, ¢ = 75.800(6)°, £ = 62.325(4)°,
V = 2955.8(4) ¡3, Dcalcd = 1.303 g cm¹3, 2ªmax = 55.0°, R1 (I >
2·(I )) = 0.0520, wR2 (I > 2·(I )) = 0.2062 for 10087 reflections
and 718 parameters, GOF = 1.610.
Crystallographic data have been deposited with Cambridge
Crystallographic Data Centre: Deposition number CCDC-750467.
Copies of the data can be obtained free of charge via http://
www.ccdc.cam.ac.uk/conts/retrieving.html (or from the Cambridge
Crystallographic Data Centre, 12, Union Road, Cambridge, CB2
1EZ, UK; Fax: +44 1223 336033; e-mail: deposit@ccdc.cam.
ac.uk).
12 H. Wada, H. Tobita, H. Ogino, Organometallics 1997, 16,
3870.
13 a) M.-J. Fernandez, P. M. Maitlis, J. Chem. Soc., Dalton
Trans. 1984, 2063. b) B. K. Campion, R. H. Heyn, T. D. Tilley,
Organometallics 1992, 11, 3918. c) M. D. Curtis, P. S. Epstein,
Adv. Organomet. Chem. 1981, 19, 213. d) I. Castillo, T. D. Tilley,
J. Am. Chem. Soc. 2001, 123, 10526.
14 C. Eaborn, D. J. Tune, D. R. M. Walton, J. Chem. Soc.,
Dalton Trans. 1973, 2255.
References
15 The low isolated yield of 2 is due to the partial decom-
position of 2 and/or 5a to unidentified materials.
16 P. Meakin, L. J. Guggenberger, W. G. Peet, E. L.
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19 P. T. Beurskens, G. Admiraal, G. Beurskens, W. P. Bosman,
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