Spectroscopic and structural studies of thermally unstable intermediates generated in the reaction of [Pt(PPh3)2(η2- C2H4)] with dihydrodisilanes

Article abstract of DOI:10.1021/om800012s

The reaction of [Pt(PPh₃)₂(η²C ₂H₄)] (1) with 1,2-dihydrodisilane HSiR ₂SiR₂H (R = Ph, Me) was investigated by NMR spectroscopy and X-ray diffraction analysis. In the case of R = Ph, the treatment of 1 with HSiPh₂SiPh₂H at -60°C afforded the disilanylplatinum hydride [Pt(PPh₃)₂(H)(SiPh₂SiPh₂H)] (2a) by an oxidative addition of Si-H to the Pt center. Complex 2a was converted to the bis(silyl)platinum complex [Pt(PPh₃)₂(SiHPh ₂)₂] (3a) by 1,2-migration of the silyl group with a first-order rate constant of 5.5(2) × 10^-4 s^-1 at -40°C. The silylplatinum hydride [Pt(PPh₃)₂(H) (SiHPh₂)] (4a) was formed by the elimination of a SiPh₂ unit from the toluene solution of 3a maintained at -20°C for 2 days. Then, the dimerization and reductive elimination of dihydrogen of 4a at room temperature afforded the symmetrical dinuclear complex [Pt(PPh ₃)(μ-SiHPh₂)]₂ (6a). Complex 6a also was obtained by an alternative method wherein 1 reacted with HSiPh ₂SiPh₂H at room temperature. In the case of R = Me, the bis(silyi)platinum complex [Pt(PPh₃)₂(SiHMe ₂)₂] (3b) was formed even at a temperature as low as -70°C; this formation reaction was considerably faster than that of 3a, and no disilanylplatinum hydride was detected. While 3b was stable below 0°C, it underwent dimerization at room temperature to afford the unsymmetrical dinuclear complex [(PPh₃)₂Pt(H)(μ-SiMe ₂)(μ-SiHMe₂)Pt(PPh₃)] (5b), in which one hydride of the Pt(PPh₃)₂ site binds to the Pt center in a terminal binding mode and the other hydride of the Pt(PPh₃) site bridges between the Pt and the Si atoms in a nonclassical 3c-2e interaction. The liberation of one PPh₃ from the Pt(PPh₃)₂ site in 5b afforded [Pt(PPh₃)(μ;-SiHMe₂)]₂ (6b), which was similar to 6a; the ₁H and ³¹P{¹H} NMR data after the addition of excess PPh₃ to 6b indicated the equilibrium between 5b and 6b. These results suggest that the reaction in the 1/HSiR₂SiR₂H system proceeds in the following order: an oxidative addition of Si-H, 1,2-migration, elimination of SiR₂, dimerization accompanying the reductive elimination of dihydrogen, and liberation of PPh₃.

Full text of DOI:10.1021/om800012s

Organometallics 2008, 27, 1929–1935
1929
Spectroscopic and Structural Studies of Thermally Unstable
Intermediates Generated in the Reaction of [Pt(PPh3)2(η2-C2H4)]
with Dihydrodisilanes
Hidekazu Arii, Makiko Takahashi, Aki Noda, Masato Nanjo, and Kunio Mochida*
Department of Chemistry, Gakushuin UniVersity, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan
ReceiVed January 8, 2008
The reaction of [Pt(PPh3)2(η2-C2H4)] (1) with 1,2-dihydrodisilane HSiR2SiR2H (R ) Ph, Me) was
investigated by NMR spectroscopy and X-ray diffraction analysis. In the case of R ) Ph, the treatment
of 1 with HSiPh2SiPh2H at -60 °C afforded the disilanylplatinum hydride [Pt(PPh3)2(H)(SiPh2SiPh2H)]
(2a) by an oxidative addition of Si-H to the Pt center. Complex 2a was converted to the bis(silyl)platinum
complex [Pt(PPh3)2(SiHPh2)2] (3a) by 1,2-migration of the silyl group with a first-order rate constant of
5.5(2) × 10-4 s-1 at –40 °C. The silylplatinum hydride [Pt(PPh3)2(H)(SiHPh2)] (4a) was formed by the
elimination of a SiPh2 unit from the toluene solution of 3a maintained at –20 °C for 2 days. Then, the
dimerization and reductive elimination of dihydrogen of 4a at room temperature afforded the symmetrical
dinuclear complex [Pt(PPh3)(µ-SiHPh2)]2 (6a). Complex 6a also was obtained by an alternative method
wherein 1 reacted with HSiPh2SiPh2H at room temperature. In the case of R ) Me, the bis(silyl)platinum
complex [Pt(PPh3)2(SiHMe2)2] (3b) was formed even at a temperature as low as -70 °C; this formation
reaction was considerably faster than that of 3a, and no disilanylplatinum hydride was detected. While
3b was stable below 0 °C, it underwent dimerization at room temperature to afford the unsymmetrical
dinuclear complex [(PPh3)2Pt(H)(µ-SiMe2)(µ-SiHMe2)Pt(PPh3)] (5b), in which one hydride of the Pt(PPh3)2
site binds to the Pt center in a terminal binding mode and the other hydride of the Pt(PPh3) site bridges
between the Pt and the Si atoms in a nonclassical 3c-2e interaction. The liberation of one PPh3 from the
1
Pt(PPh3)2 site in 5b afforded [Pt(PPh3)(µ-SiHMe2)]2 (6b), which was similar to 6a; the H and 31P{1H}
NMR data after the addition of excess PPh3 to 6b indicated the equilibrium between 5b and 6b. These
results suggest that the reaction in the 1/HSiR2SiR2H system proceeds in the following order: an oxidative
addition of Si-H, 1,2-migration, elimination of SiR2, dimerization accompanying the reductive elimination
of dihydrogen, and liberation of PPh3.
synthesized by the reactions of Pt(0) complexes with primary
silanes SiH3R and secondary silanes SiH2R2 via intermediates
such as silylplatinum(II) hydride and bis(silyl)platinum(II)
complexes, respectively.4,5
Introduction
The activation of the Si-H and Si-Si bonds by metal
complexes is one of the important steps in the syntheses of new
organosilane compounds.1,2 A zerovalent platinum complex is
well known as a catalyst for the insertion reaction. A silylplati-
num species is considered as an intermediate during the reaction
and has been synthesized by a Si-H oxidative addition of
hydrosilanes to Pt(0) complexes and a salt elimination from
Pt(II) halide complexes on reaction with silyllithium com-
pounds.3 The treatment of Pt(0) complexes with SiHnR4-n in
various molar ratios affords silylplatinum(II) hydride and
bis(silyl)platinum(II) complexes by the oxidative addition of
the Si-H bond. Di- and trinuclear platinum complexes are
Furthermore, the reactions of Pt(0) complexes with disilanes
HnSiR3-nSiR3-nHn containing a Si-Si bond as well as a Si-H
bond have been studied.6 On the basis of the 1H NMR signals,
Fink and Michalczyk et al. have reported that the mononuclear
[Pt(dcpe)(SiH2SiH3)2] (dcpe ) 1,2-bis(dicyclohexylphosphino)-
ethane) and dinuclear complexes [Pt(dcpe)(µ-1,2-SiH2SiH2)]2 were
generated in a 4:1 ratio when H3SiSiH3 is rapidly added to a
solution of [Pt(dcpe)(H)2] in toluene and that the structures of both
(4) (a) Zarete, E. A.; Tessier-Youngs, C. A.; Youngs, W. J. J. Am. Chem.
Soc. 1988, 110, 4068–4070. (b) Sanow, L. M.; Chai, M.; McConnville,
D. B.; Galat, K. J.; Simons, R. S.; Rinaldi, P. L.; Youngs, W. J.; Tessier,
C. A. Organometallics 2000, 19, 192–205. (c) Tanabe, M.; Yamada, T.;
Osakada, K. Organometallics 2003, 22, 2190–2192. (d) Tanabe, M.; Ito,
D.; Osakada, K. Organometallics 2007, 26, 459–462. (e) Braddock-Wilking,
J.; Levchinsky, Y.; Rath, N. P. Organometallics 2000, 19, 5500–5510. (f)
Shimada, S.; Li, Y.-H.; Rao, M. L.; Tanaka, M. Organometallics 2006, 25,
3796–3798.
* Corresponding author. Tel: +81-3-3986-0221. Fax: +81-3-5992-1029.
E-mail: kunio.mochida@gakushuin.ac.jp.
(1) Sharma, H. K.; Pannell, K. H. Chem. ReV. 1995, 95, 1351–1374.
(2) Corey, J. Y.; Braddock-Wilking, J. Chem. ReV. 1999, 99, 175–292.
(3) (a) Ozawa, F.; Kamite, J. Organometallics 1998, 17, 5630–5639.
(b) Roy, A. K.; Taylor, R. B. J. Am. Chem. Soc. 2002, 124, 9510–952. (c)
Kang, Y.; Kang, S.; Ko, J. Organometallics 2000, 19, 1216–1224. (d) Tsuji,
Y.; Nishiyama, K.; Hori, S.; Ebihara, M.; Kawamura, T. Organometallics
1998, 17, 507–512. (e) Hashimoto, H.; Sekiguchi, A.; Iwamoto, T.; Kabuto,
C.; Kira, M. Organometallics 2002, 21, 454–456. (f) Kim, Y.-J.; Choi, E.-
H.; Lee, S. W. Organometallics 2003, 22, 3316–3319. (g) Shimada, S.;
Rao, M. L. N.; Li, Y.-H.; Tanaka, M. Organometallics 2005, 24, 6029–
6036. (h) Goikhman, R.; Karakuz, T.; Shimon, L. J. W.; Leitus, G.; Milstein,
D. Can. J. Chem. 2005, 83, 786–792. (i) Sagawa, T.; Asano, Y.; Ozawa, F.
Organometallics 2002, 21, 5879–5886.
(5) (a) Osakada, K.; Tanabe, M.; Tanase, T. Angew. Chem., Int. Ed.
2000, 39, 4053–4055. (b) Braddock-Wilking, J.; Corey, J. Y.; Dill, K.; Rath,
N. P. Organometallics 2002, 21, 5467–5469.
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J. Am. Chem. Soc. 1992, 114, 7955–7957. (b) Pham, E. K.; West, R. J. Am.
Chem. Soc. 1989, 111, 7667–7668. (c) Yamashita, H.; Tanaka, M.; Goto,
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10.1021/om800012s CCC: $40.75
2008 American Chemical Society
Publication on Web 03/20/2008

1930 Organometallics, Vol. 27, No. 8, 2008
Arii et al.
the complexes were identified by X-ray diffraction (XRD) analysis.
1
Moreover, it was confirmed by H NMR spectroscopy that the
treatment of [Pt(dcpe)(H)2] with H2SiMeSiMeH2 afforded the
bis(silyl)platinum(II) complex [Pt(dcpe)(SiH2Me)2] via the disila-
nylplatinum(II) hydride complex [Pt(dcpe)(H)(SiHMeSiH2Me)].6a
It has been clarified by West and co-workers that the η2-disilene
i
platinum complex [Pt(dppe)(η2-Si2 Pr4)] (dppe ) 1,2-bis(diphe-
nylphosphino)ethane) was obtained when the Pt(0)-olefin complex
[Pt(dppe)(η2-C2H4)] reacted with HSiiPr2SiiPr2H in toluene.6b
We are eager to study the reaction behavior of a zerovalent
platinum complex with compounds of group 14 elements and
have synthesized many silylplatinum and germylplatinum com-
plexes.7 Among them, the reaction of [Pt(PPh3)2(η2-C2H4)] with
a silylgermyl compound HGePh2(SiMe2)2GePh2H afforded
[Pt(PPh3)2{GePh2(SiMe2)2GePh2}] with a five-membered ring
of PtSi2Ge2.8 In this paper, we report the resolution of the
structures of the intermediates in the reaction of [Pt(PPh3)2(η2-
C2H4)] (1) with 1,2-dihydrodisilane HSiR2SiR2H (R ) Ph, Me)
from -60 °C to room temperature by NMR spectroscopy and
XRD analysis.
Figure 1. 31P{1H} NMR spectra for the reaction of 1 with
HSiPh2SiPh2H at -60 °C for 10 min after mixing (A) and for 3 h
after mixing (B). The solution B was standing at –30 °C for 10
min (C).
Results and Discussion
Reaction of Complex 1 with HSiR2SiR2H below -30
°C. When complex 1 was reacted with HSiPh2SiPh2H in
toluene-d8 at -60 °C, a new species was formed during the
progress of the reaction. In the 1H NMR spectra, multiple peaks
were observed in the aromatic region of 7–8 ppm (Figures S1,
S2). A new intense peak at 5.30 ppm exhibited the evolution
of free ethylene gas attributed to the liberation from the platinum
center in 1, and the new Si-H peak at 5.71 ppm with 195Pt
satellites appeared at a lower magnetic field than the Si-H peak
in the starting material HSiPh2SiPh2H. A Pt-H peak was
observed centered at -1.83 ppm as a doublet of doublets with
195Pt satellites and was similar to that of the platinum hydride
complexes reported hitherto.9 One of the two Si-H bonds in
(2)
at 5.5(2) × 10-4 s-1 from the ratio of the area of the peak at
7.82 ppm of 2a to that of a residual protio toluene-d8 at 2.09
ppm (Figure S3). In the 1H NMR spectra for the conversion of
2a to 3a (Figure S1), the peaks in the aromatic region showed
two phenyl groups, of which one was attached on the P atoms
and the other is on the Si atoms. The terminal Si-H and Pt-H
signals disappeared, and a new Si-H signal appeared at 5.80
ppm as a triplet with 195Pt satellites, although it resembled a
septet due to an overlay of the satellites. Furthermore, a peak
due to the dihydrogen was not detected around 4.5 ppm. In the
31P{1H} NMR spectra (Figure 1), two doublets disappeared and
a singlet with the 195Pt satellites appeared at 31.6 ppm. The
1
Si-H signal and no detection of dihydrogen in the H NMR
spectral change of the toluene-d8 solution of 2a support that 3a
is assigned not to an η2-disilene platinum complex but to a
bis(silyl)platinum complex.
On the other hand, 1 reacted with HSiMe2SiMe2H rapidly
even at -70 °C to obtain the bis(silyl)platinum(II) complex
[Pt(PPh3)2(SiHMe2)2] (3b; eq 3) without the any evidence for
the formation of a disilanylplatinum(II) hydride similar to 2a.
The small methyl groups on the Si atom make the silyl groups
(1)
the disilane permits the platinum atom to undergo oxidative
addition, and the other remains on the second silicon atom,
consistent with the formation of the disilanylplatinum(II) hydride
complex [Pt(PPh3)2(H)(SiPh2SiPh2H)] (2a; eq 1). In the 31P{1H}
NMR spectrum (Figure 1), two doublets with 195Pt satellites
were observed at 37.4 and 31.5 ppm, indicating that the
phosphine atoms of PPh3 are nonequivalent. Complex 2a is
thermally unstable and is converted slowly at -60 °C and
rapidly at -30 °C to the bis(silyl)platinum complex
[Pt(PPh3)2(SiHPh2)2] (3a; eq 2). The conversion of 2a to 3a
obeyed a first-order rate law, and the rate constant was estimated
(3)
SiHMe2 more reactive to the Pt center as compared with the
SiHPh2 units; due to this, 2b is converted to 3b more rapidly
than 2a to 3a. In the NMR spectrum of 3b, the Si-H signal
appeared as a triplet of septets at 4.42 ppm, and the Si-Me
signals appeared as a doublet with the 195Pt satellites. The signals
for the 31P nuclei were observed as a singlet at 34.9 ppm with
the 195Pt satellites. Moreover, both 3a and 3b were less thermally
stable in contrast to other bis(silyl)platinum complexes reported
hitherto, which were stable at room temperature.3a,6a,d,7a,10 The
conversions of 3a and 3b commenced above -20 and 0 °C,
respectively, which are described in the next section. It is
proposed that an arylphosphine PPh3 causes the low thermal
stability because complexes with high thermal stability contain
(7) (a) Mochida, K.; Wada, T.; Suzuki, K.; Hatanaka, W.; Nishiyama,
Y.; Nanjo, M.; Sekine, A.; Ohashi, Y.; Sakamoto, M.; Yamamoto, A. Bull.
Chem. Soc. Jpn. 2001, 74, 123–137. (b) Usui, Y.; Fukushima, T.; Nanjo,
M.; Mochida, K.; Akasaka, K.; Kudo, T.; Komiya, S. Chem. Lett. 2006,
35, 810–811. (c) Mochida, K.; Fukushima, T.; Suzuki, M.; Hatanaka, W.;
Takayama, M.; Usui, Y.; Nanjo, M.; Akasaka, K.; Kudo, T.; Komiya, S. J.
Organomet. Chem. 2007, 692, 395–401.
(8) Usui, Y.; Hosotani, S.; Ogawa, A.; Nanjo, M.; Mochida, K.
Organometallics 2005, 24, 4337–4339.
(9) (a) Azizian, H.; Dixon, K. R.; Eaborn, C.; Pidcock, A.; Shuaib, N. M.;
Vinaixa, J. J. Chem. Soc., Chem. Commun. 1982, 1020–1022. (b) Packett,
D. L.; Syed, A.; Trogler, W. C. Organometallics 1988, 7, 159–166. (c)
Chan, D.; Duckett, S. B.; Heath, S. L.; Khazal, I. G.; Perutz, R. N.; Sabo-
Etienne, S.; Timmins, P. L. Organometallics 2004, 23, 5744–5756.

Reaction of [Pt(PPh3)2(η2-C2H4)] with Disilanes
Organometallics, Vol. 27, No. 8, 2008 1931
Figure 3. Crystal structure of 4a, showing 50% probability thermal
ellipsoids. The hydrogen atoms except for ones on Si and Pt are
omitted for clarity. Selected bond lengths (Å) and angles (deg):
Pt(1)-P(1) 2.2900(14), Pt(1)-P(2) 2.3140(14), Pt(1)-Si(1) 2.3368-
(17),Pt(1)-H(1h)1.885(3),P(1)-Pt(1)-P(2)111.98(5),P(1)-Pt(1)-
Si(1) 95.95(6), P(1)-Pt(1)-H(1h) 166.4(7), P(2)-Pt(1)-Si(1)
152.08(6), P(2)-Pt(1)-H(1h) 80.97(10), Si(1)-Pt(1)-H(1h)
71.19(9).
The P-Pt-Si(trans to P) bond angles in 3b are 160° and 155°
less than that of 3a and the reported bis(silyl)platinum com-
plexes, which implies that the coordination plane in 3b is rather
distorted.
Hence, the single Si-H oxidative addition of HSiPh2SiPh2H
to the Pt center in 1 affords 2a with the elimination of ethylene;
subsequently, the terminal SiHPh2 of the disilanyl unit in 2a is
transferred to the Pt center to generate complex 3a. The
bis(silyl)platinum complex 3b is rapidly generated even at -70
°C during the reaction of 1 with HSiMe2SiMe2H, although 2b
could not be detected. It is possible that 2b is formed transiently
and rapidly converted to 3b by analogy to the results for
HSiPh2SiPh2H.
Change in [Pt(PPh3)2(SiHR2)2] (3a, 3b). We attempted to
examine the change in 3a at -20 °C in toluene-d8. The 1H NMR
spectrum of the aromatic region in the toluene-d8 solution of
3a (after allowing the solution to stand for 2 days at -20 °C)
showed the presence of the silylplatinum(II) hydride complex
cis-[Pt(PPh3)2(H)(SiHPh2)] (4a; eq 4) and a few minor products
(Figure S4). The NMR data of 4a are consistent with that
reported by Braddock-Wilking et al. in a reaction of 1 with a
monosilane SiH2Ph2.12
Figure 2. Crystal structure of 3a (A) and 3b (B) showing 50%
probability thermal ellipsoids. The hydrogen atoms except for one
on Si are omitted for clarity. Selected bond lengths (Å) and angles
(deg), 3a: Pt(1)-P(1) 2.3599(17), Pt(1)-P(2) 2.3767(18), Pt(1)-Si(1)
2.358(2), Pt(1)-Si(2) 2.3973(19), Si(1)-Si(2) 3.069(3); P(1)-
Pt(1)-P(2) 96.54(6), P(1)-Pt(1)-Si(1) 96.98(7), P(1)-Pt(1)-Si(2)
177.20(7), P(2)-Pt(1)-Si(1) 165.94(6), P(2)-Pt(1)-Si(2) 86.16(6),
Si(1)-Pt(1)-Si(2) 80.37(7); 3b: Pt(1)-P(1) 2.3382(18), Pt(1)-P(2)
2.3452(16), Pt(1)-Si(1) 2.3828(19), Pt(1)-Si(2) 2.4019(19),
Si(1)-Si(2) 3.134(3); P(1)-Pt(1)-P(2) 104.17(6), P(1)-Pt(1)-Si(1)
93.57(7), P(1)-Pt(1)-Si(2) 159.82(6), P(2)-Pt(1)-Si(1) 155.49(6),
P(2)-Pt(1)-Si(2) 86.72(6), Si(1)-Pt(1)-Si(2) 81.85(7).
aliphatic alkylphosphines such as PEt3 and dcpe. Both 3a and
3b were obtained as crystals suitable for XRD analysis due to
its thermal stability below -30 °C.
The Pt atom in the crystal structures of both 3a and 3b has
a four-coordinate square-planar geometry with a P2Si2 donor
set (Figure 2), and the bond lengths of Pt-Si are similar to
those of bis(silyl)platinum(II) complexes reported previously.7a,10
The bond distances between platinum and the hydrides on the
Si atoms in 3a and 3b are more than 3 Å, and the two hydrides
are not bridged between the Pt and Si atoms but are localized
on each Si atom. The bond distances of Si(1)-Si(2) in 3aand
3b are 3.07 and 3.14 Å, respectively; these are beyond the range
of a Si-Si single bond in cyclic compounds (2.21–2.51 Å),11
indicating that there is no interaction between the two Si atoms.
(4)
4a (Figure 3) is determined to be the silylplatinum(II) hydride
complex cis-[Pt(PPh3)2(H)(SiHPh2)] by XRD analysis, wherein
formally one of the two silyl groups in 3a is liberated as a
silylene group :SiPh2 and the hydride remains on Pt. The two
hydrides H(1h) and H(1s) determined by difference Fourier
maps are localized on Pt(1) and Si(1), respectively. The bond
length of Pt(1)-Si(1) is shorter than that in the silylplatinum
(10) (a) Pham, E. K.; West, R. Organometallics 1990, 9, 1517–1523.
(b) Kim, Y.-J.; Park, J.-I.; Lee, S.-C.; Osakada, K.; Tanabe, M.; Choi, J.-
C.; Koizumi, T.; Yamamoto, T. Organometallics 1999, 18, 1349–1352.
(11) Kaftory, M.; Kapon, M.; Botoshansky, M. In The Chemistry of
Organic Silicon Compounds; Rappoport, Z., Apeloig, Y., Eds.; Wiley: New
York, 1998; Vol. 2, Part 1, p 202.
(12) Braddock-Wilking, J.; Corey, J. Y.; Trankler, K. A.; Xu, H.; French,
L. M.; Praingam, N.; White, C.; Rath, N. P. Organometallics 2006, 25,
2859–2871.

1932 Organometallics, Vol. 27, No. 8, 2008
Arii et al.
hydride complexes with a tertiary silane reported previously,
although the Pt-P bond lengths are similar to them.13 The
terminal Pt-H bond is 1.885(3) Å, longer than that found in
the platinum complexes with a terminal hydride.9c,12,14,15b
Complex 4a has been already synthesized by Pidcock et al. in
1974, but it could not be isolated as a powder or crystals owing
to its low thermal stability.16 We have succeeded in isolating
4a as single crystals as well as in synthesizing it by an alternative
method using the dihydrodisilane HSiPh2SiPh2H. Unfortunately,
we have no proof for the silylene elimination, which is a key
step in the conversion.
In the case of complex 3b, the 1H and 31P{1H} NMR spectra
showed few changes in the range -20 to 0 °C. After the solution
1
was allowed to stand at room temperature overnight, the H
and 31P{1H} NMR spectra indicated a loss of 3b and formation
of the unsymmetrical diplatinum complex [(PPh3)2Pt(H)(µ-
SiMe2)(µ-SiHMe2)Pt(PPh3)] (5b; eq 5), and no silylplatinum(II)
Figure 4. Variable-temperature 1H NMR spectra in the Si-Me
region of 5b.
1
hydride complex was observed. In the H NMR spectrum of
(5)
5b measured at -70 °C in CD2Cl2 (Figure S5), the Si-Me
signals were observed as two resonances of a singlet at 0.11
and -0.43 ppm, and the Pt-H signals were observed as a
doublet at 0.70 ppm in the region of the hydride bridged between
Pt and Si and a triplet with two sets of satellites at -7.05 ppm
in the region of the terminal hydride on Pt. These resonances
were observed at a magnetic field higher than that of the
unsymmetrical diplatinum complex bearing silafluorenyl units,17
causing an electronic deficiency on the Si atom included in the
Figure 5. Crystal structure of 5b, showing 50% probability thermal
ellipsoids. The hydrogen atoms except for H1 and H2 are omitted
for clarity. Selected bond lengths (Å) and angles (deg): Pt(1)-Pt(2)
2.7518(2), Pt(1)-P(1) 2.2826(11), Pt(1)-P(2) 2.3268(12), Pt(1)-Si(1)
2.4602(12), Pt(1)-Si(2) 2.3509(13), Pt(1)-H(1) 1.57(5), Pt(2)-P(3)
2.2477(11), Pt(2)-Si(1) 2.3464(12), Pt(2)-Si(2) 2.4241(12),
Pt(2)-H(2) 1.63(5), Si(1)-H(1) 1.79(5), Si(2)-H(2) 1.95(5); P(1)-
Pt(1)-P(2) 118.49(4), P(1)-Pt(1)-Si(1) 118.35(4), P(1)-Pt(1)-
Si(2) 99.21(4), P(1)-Pt(1)-Pt(2) 125.34(3), P(2)-Pt(1)-Si(1)
107.23(4), P(2)-Pt(1)-Si(2) 102.53(4), P(2)-Pt(1)-Pt(2) 114.51(3),
Si(1)-Pt(1)-Si(2) 109.18(4), P(3)-Pt(2)-Si(1) 98.63(4), P(3)-
Pt(2)-Si(2) 150.80(4), Si(1)-Pt(2)-Si(2) 110.57(4), P(3)-Pt(2)-
Pt(1) 155.59(3).
complexes containing Pt-Pt single bonds.4,19 The two hydrides
are determined by difference Fourier maps and are bridged
between Pt and Si. 5b exhibits two alternating long/short Pt-Si
bonds in which the long Pt-Si bonds are associated with a
nonclassical 3c-2e interaction. However, one of the two
hydrides binds to the Pt center as a terminal hydride, as
determined from NMR experiments, wherein the Pt-H signals
were observed at an upfield resonance of –7.05 ppm. Braddock-
Wilking and co-workers have reported that the hydride of the
Pt(PPh3)2 site is a terminal binding mode in the unsymmetrical
diplatinum complex with silafluorenyl units.17 From a 1H-31P
HMBC experiment of 5b (Figure S6), the terminal hydride at
-7.05 ppm correlated to the doublet signal of the Pt(PPh3)2
site, and the bridged hydride at 0.70 ppm correlated to the triplet
signal of the Pt(PPh3) site. Hence, in solution, the hydride (H1)
1
aromatic ring. The variable-temperature H NMR data of 5b
from -80 to 20 °C showed a dynamic behavior, and the
coalescence temperature was determined to be –30 °C (Figure
4). The behavior concerns an intra- or intermolecular exchange
of PPh3 between the Pt(PPh3)2 and Pt(PPh3) sites. The trialkyl-
phosphine exchange has been reported in related unsymmetrical
dinuclear palladium complexes.18 The 31P{1H} NMR spectra
(Figure S5) showed a triplet at 31.7 ppm assignable to the
resonance of the 31P nuclei on the Pt(PPh3) side and a doublet
at 22.4 ppm for the P nuclei on the Pt(PPh3)2 side.
In the crystal structure of 5b (Figure 5), Pt(1) has a tetrahedral
geometry with a P2Si2 donor set, and Pt(2) has a planar geometry
with a PSi2 donor set. The two platinum atoms are bridged by
two SiHMe2 groups, and the bond distance of Pt(1)-Pt(2) is
2.7535(5) Å longer than that of the symmetrical diplatinum
(13) (a) Latif, L. A.; Eaborn, C.; Pidcock, A. P.; Weng, N. S. J.
Organomet. Chem. 1994, 474, 217–221. (b) Koizumi, T.; Osakada, K.;
Yamamoto, T. Organometallics 1997, 16, 6014–6016.
(14) White, C. P.; Braddock-Wilking, J.; Corey, J. Y.; Xu, H.; Redekop,
E.; Sedinkin, S.; Rath, N. P. Organometallics 2007, 26, 1996–2004.
(15) Kloek, S. M.; Goldberg, K. I. J. Am. Chem. Soc. 2007, 129, 3460–
3461.
(16) Eaborn, C.; Ratcliff, B.; Pidcock, A. J. Organomet. Chem. 1974,
65, 181.
(17) (a) Braddock-Wilking, J.; Corey, J. Y.; Trankler, K. A.; Dill, K. M.;
French, L. M.; Rath, N. M. Organometallics 2004, 23, 4576–4584. (b)
Braddock-Wilking, J.; Corey, J. Y.; French, L. M.; Choi, E.; Speedie, V. J.;
Rutherford, M. F.; Yao, S.; Xu, H.; Rath, N. P. Organometallics 2006, 25,
3974–3988.
(18) Kim, Y.-J.; Lee, S.-C.; Park, J.-I.; Osakada, K.; Choi, J.-C.;
Yamamoto, T. Organometallics 1998, 17, 4929–4931.
(19) Taylor, N. J.; Chieh, P. C.; Carty, A. J. J. Chem. Soc., Chem.
Commun. 1975, 448–449.

Reaction of [Pt(PPh3)2(η2-C2H4)] with Disilanes
Organometallics, Vol. 27, No. 8, 2008 1933
of the Pt(PPh3)2 site of 5b is localized on the Pt atom as a
terminal hydride.
Conversion to Symmetrical Dinuclear Complexes
1
[Pt(PPh3)(µ-SiHR2)]2 (6a, 6b). When the H NMR signal of
4a recorded after allowing it to stand in toluene-d8 or CD2Cl2
at room temperature overnight decreased, the symmetrical
diplatinum complex [Pt(PPh3)(µ-SiHPh2)]2 (6a; eq 6) was
crystallized in the NMR tube due to the its low solubility in
toluene. Complex 4a is converted into 6a by dimerization and
(6)
Figure 6. Crystal structure of 6b, showing 50% probability thermal
ellipsoids. The hydrogen atoms are omitted for clarity. Selected
bond lengths (Å) and angles (deg): Pt(1)-Pt(1)* 2.7010(4),
Pt(1)-P(1) 2.2537(15), Pt(1)-Si(1) 2.4273(16), Pt(1)-Si(1)*
2.3304(16), Pt(1)-H(1) 1.86(8), Si(1)-H(1) 1.70(8); P(1)-Pt(1)-
Si(1) 145.12(6), P(1)-Pt(1)-Si(1)* 103.78(6), Si(1)-Pt(1)-Si(1)*
110.85(4), P(1)-Pt(1)-Pt(1)* 160.52(4).
reductive elimination of dihydrogen on Pt. Complex 6a was
also afforded by the treatment of 1 with HSiPh2SiPh2H in
toluene at room temperature, which implies that 2a, 3a, and 4a
are intermediates in the process when 1 is reacted with
HSiPh2SiPh2H to form 6a. The structure of 6a was confirmed
by XRD analysis, wherein the hydride of SiHPh2 is bridged
between Pt and Si in an η2-binding fashion, and is consistent
with the crystal structural data reported previously.20 The
bis(silyl)platinum complex with silafluorenyl units and 3b
provided the corresponding unsymmetrical dinuclear com-
plexes,17 but the unsymmetrical dinuclear complex [(PPh3)2Pt-
(H)(µ-SiPh2)(µ-SiHPh2)Pt(PPh3)] (5a) during the conversion of
pattern associated with a diplatinum complex. Moreover, when
excess PPh3 was added to 6b, the 1H and 31P{1H} spectra
showed only regeneration of 5b without the formation of other
species. The conversion of 5b to 6b in solution indicates the
equilibrium between them for the liberation/rebinding of PPh3
to the Pt(PPh3)2 center. The Pt centers in the crystal structure
of 6b (Figure 6) have a three-coordinate planar geometry and
are bridged by two SiHMe2 groups. The bond lengths and angles
are similar to those of the symmetrical dipalladium and
diplatinum complexes.4,22 Complex 6b was synthesized by the
reaction of 1 with the monosilane Me2SiH2 at a molar ratio of
1:4,20a but the crystal structure has not been reported yet. The
treatment of 1 with HSiMe2SiMe2H at room temperature does
not afford the symmetrical complex 6b, but an unsymmetrical
complex 5b; this is in contrast to the HSiPh2SiPh2H system,
where the symmetrical complex 6a is obtained as the product.
The difference in the products formed may be due to the steric
repulsion between the alkyl groups on Si and P. The substitution
of the phenyl group on Si with a methyl group decreases the
steric repulsion and keeps PPh3 bound to the Pt(PPh3)2 center
in order to maintain the unsymmetrical structure of 5b.
Hence, the reaction scheme of 1 with general dihydrodisilanes
can be described as follows (Scheme 1): A disilanyl platinum
hydride complex 2 is generated by the oxidative addition of
one Si-H in HSiR2SiR2H to the Pt center of 1. Complex 2
rapidly converts into the bis(silyl)platinum complex 3 by 1,2-
migration. The elimination of silylene leads to the conversion
of 3 into the silylplatinum hydride complex 4. The unsym-
metrical dinuclear complex 5 is generated by dimerization and
reductive elimination of H2 of 4. One PPh3 is liberated from
the Pt(PPh3)2 site of 5 in order to decrease the steric repulsion
between PPh3 and SiR2; finally, the symmetrical dinuclear
complex 6 is generated.
1
4a into 6a could not be detected with H and 31P{1H} NMR
spectroscopy. The steric repulsion between PPh3 and SiHPh2 is
expected to increase if [(PPh3)2Pt(H)(µ-SiPh2)(µ-SiHPh2)-
Pt(PPh3)] (5a) was generated transiently. Therefore, one PPh3
group of the Pt(PPh3)2 site is liberated from the Pt atom to
minimize the repulsion; due to this, the symmetrical dinuclear
complex 6a is generated from 4a without the detection of the
unsymmetrical one. In fact, when [Pt(PMePh2)2(µ-SiH(IMP))]2
(IMP ) 2-isopropyl-6-methylphenyl), which is stable in the solid
state, is dissolved in organic solvents, one PMePh2 group was
liberated from the Pt atom despite the expected lower hindrance
of the phosphine, PMePh2, as compared to PPh3 to form [Pt-
(PMePh2)(µ-SiH(IMP))]2.21
In the case of R ) Me, 5b is converted into the symmetrical
diplatinum complex [Pt(PPh3)(µ-SiHMe2)]2 (6b; eq 7) by the
liberation of one PPh3 from the Pt(PPh3)2 site. In the 1H NMR
(7)
spectra of 6b, the Pt-H-Si and Si-Me signals were observed
as a singlet at 1.58 and 0.22 ppm, respectively. The 31P{1H}
NMR data of 6b exhibited part of an AA′XX′ spin system
(22) Kim, Y.-J.; Lee, S.-C.; Park, J.-I.; Osakada, K.; Choi, J.-C.;
Yamamoto, T. J. Chem. Soc., Dalton Trans. 2000, 417–421.
(20) (a) Auburn, M.; Ciriano, M.; Howard, J. A. K.; Murray, M.; Pugh,
N. J.; Spencer, J. L.; Stone, F. G. A.; Woodward, P. J. Chem. Soc., Dalton
Trans. 1980, 659–666. (b) White, C. P.; Braddock-Wilking, J.; Corey, J. Y.;
Xu, H.; Redekop, E.; Sedinkin, S.; Rath, N. M. Organometallics 2007, 26,
1996–3988.
(23) (a) Cook, C. D.; Jauhal, G. S. J. Am. Chem. Soc. 1968, 90, 1464–
1467. (b) Ugo, R.; Caliati, F.; LaMonica, G. Inorg. Synth. 1968, 11, 106.
(24) Boudjouk, P.; Han, B. H. Tetrahedron Lett. 1981, 22, 3813–3814.
(25) (a) Sakurai, H.; Tominaga, K.; Watanabe, T.; Kumada, M.
Tetrahedron Lett. 1966, 7, 5493–5497. (b) Nares, K. E.; Harris, M. E.;
Ring, M. A.; O’Neal, H. E. Organometallics 1989, 8, 1964–1967.
(21) Braddock-Wilking, J.; Levchinsky, Y.; Rath, N. P. Organometallics
2001, 20, 474–480.

1934 Organometallics, Vol. 27, No. 8, 2008
Arii et al.
Scheme 1
Table 1. Crystallographic Data
3a · C7H8
3b
4a · C7H8
5b · C7H8
6b
formula
fw
cryst syst
space group
a, Å
b, Å
c, Å
R, deg
ꢀ, deg
γ, deg
V, Å3
Z
C67H60P2PtSi2
1178.36
C40H44P2PtSi2
837.96
C55H50P2PtSi
996.07
C65H67P3Pt2Si3
1387.46
monoclinic
P21/c (#14)
16.7770(7)
21.2150(9)
16.8200(5)
90
106.959(3)
90
5726.3(4)
4
1.609
5.046
52 978
13 701
655
0.0404
0.1186
C20H22PPtSi
516.53
triclinic
monoclinic
P21/n (#14)
11.1420(9)
15.2450(5)
21.5240(14)
90
91.594(3)
90
3654.6(4)
4
1.523
4.020
32 727
8545
triclinic
triclinic
j
j
j
P1 (#2)
P1 (#2)
P1 (#2)
12.6440(13)
14.1320(11)
17.0186(15)
73.490(5)
86.090(5)
83.673(5)
2895.2(5)
2
1.352
2.559
27 413
12 593
9.5937(2)
11.1677(2)
21.3492(3)
97.0400(10)
94.1000(10)
98.4360(10)
2236.19(7)
2
1.479
3.273
17 514
10 680
8.8370(3)
9.8380(6)
13.3330(8)
80.115(3)
73.335(4)
82.170(4)
1089.32(10)
2
1.575
6.566
10 112
4746
F
calcd, g cm-3
µ(Mo KR), cm-1
total no. of data
no. of unique data
no. of params
R1a
655
0.0632
0.1794
412
0.0503
0.1306
541
0.0505
0.1238
211
0.0438
0.1420
wR2 (all data)b
2
1/2
a I > 2.00σ(I). R1 ) ∑||Fo| - |Fc||/∑|Fo|. b wR2 ) {∑(w(|Fo| - |Fc|)2)/∑wFo
} .
In the conversion of disilanylplatinum hydride complexes,
West and co-workers have reported that two Si-H oxidative
additions occur in the reaction of [Pt(dppe)(η2-C2H4)] with
Experimental Section
General Procedure. All the experiments were carried out using a
standard vacuum line and Schlenk techniques or in an M. Braun inert
atmosphere drybox. All the reagents were of the highest grade available
and were used without further purification. All the solvents used for
the syntheses were distilled according to the general procedure.
Benzene-d6 and toluene-d8 were distilled from potassium metal under
Ar atmosphere. CD2Cl2 was dried over activated 4 Å molecular sieves.
Complex 123 and HSiR2SiR2H (R ) Ph,24 Me25) were synthesized
i
HSiR2SiR2H (R ) Me, Pr) to afford the η2-disilene platinum
complex [Pt(dppe)(η2-Si2R4)] as a major product and 1,2-
migration product [Pt(dppe)(SiHR2)2] as the minor one.10a In
contrast, Tilley and co-workers proved on the basis of NMR
analysis that the treatment of [Pt(PEt3)3] with H2SiPhSiPhH2
yields only one product, cis-[Pt(PEt3)2(SiH2Ph)2].6d In our
system, the bis(silyl)platinum complex is obtained as the major
product below -30 °C, and the other products could not be
detected by NMR.
1
according to the previously reported method. The H NMR spectral
measurements were performed on a JEOL AL-300 NMR spectrometer
at 300 MHz for 1H and 122 MHz for 31P. The chemical shifts of the
protons are reported relative to the residual protonated solvents
benzene-d6 (7.15 ppm), toluene-d8 (2.09 ppm), and CD2Cl2 (5.32 ppm).
The chemical shifts of phosphine are corrected relative to external
H3PO4 (0 ppm). Elemental analysis was performed on a CE Instru-
ments EA1110 corrected by acetoanilide.
Conclusion
The reaction of [Pt(PPh3)2(η2-C2H4)] (1) with disilanes
HSiR2SiR2H (R ) Ph, Me) was investigated by 1H and 31P{1H}
NMR spectroscopy and XRD analysis. In the case of
HSiPh2SiPh2H, complex 1 changed to the symmetrical diplati-
num complex [Pt(PPh3)(µ-SiHPh2)]2 (6a) via three intermediates
in the following order: the disilanylplatinum hydride (2a), the
bis(silyl)platinum (3a), and the silylplatinum hydride (4a). 4a
was obtained from the toluene solution of 3a by the elimination
of a SiPh2 unit, although it has been synthesized by the treatment
of 1 with Ph2SiH2. In HSiMe2SiMe2H, the sterically minimized
alkyl substituents, methyl groups, caused the conversion of 1
to the unsymmetrical diplatinum complex 5b and the observation
of only the intermediate 3b in the reaction. These mononuclear
silylplatinum complexes bearing PPh3 were more thermally
unstable than that of aliphatic alkylphosphine ligands.
Syntheses of Platinum Complexes. [Pt(PPh3)2(H)(SiPh2-
SiHPh2)] (2a). To an H-shape glass tube attached to an NMR tube
was added a toluene solution (0.3 mL) of HSiPh2SiPh2H (7.4 mg,
0.020 mmol) to the NMR tube side, and a toluene solution (0.4
mL) of [Pt(PPh3)2(η2-C2H4)] (1) (15 mg, 0.020 mmol) was added
to the other side. After the disilane solution was frozen by liquid
N2, a small portion of the solution of 1 was poured into the NMR
tube side so that the disilane solution did not melt. The NMR tube
was sealed with the solution frozen by liquid N2 and then was stored
in a cold methanol bath at -80 °C. The solution was mixed by
shaking carefully and placed into the NMR probe controlled at -60
1
3
°C. H NMR (toluene-d8, 300 MHz, -60 °C): δ 7.82 (d, JHH
6.6 Hz), 7.66 (m, ArH), 7.5–7.3 (m, ArH), 7.2–6.6 (m, ArH), 5.71
(s, JPtH ) 56 Hz, SiH), 5.30 (s, C2H4), -1.83 (dd, JPtH ) 923
)
2
1

Reaction of [Pt(PPh3)2(η2-C2H4)] with Disilanes
Organometallics, Vol. 27, No. 8, 2008 1935
2
Hz, JPH ) 153 Hz (trans), 20 Hz (cis), PtH). 31P{1H} NMR
2JPtP ) 121 Hz, 3JPP ) 29 Hz). Calcd for 5b · C7H8 (C65H67P3Pt2Si2):
C, 56.27; H, 4.87. Found: C, 56.10; H, 4.90.
1
2
(toluene-d8, 122 MHz, -60 °C): δ 37.4 (d, JPtP ) 1785 Hz, JPP
) 11 Hz, PPh3 cis to H), 31.5 (d, 1JPtP ) 2521 Hz, 2JPP ) 10 Hz,
PPh3 trans to H).
[Pt(PPh3)2(SiHPh2)2] (3a). To a toluene solution (2 mL) of 1
(100 mg, 0.134 mmol) was added a toluene solution (2 mL) of
HSiPh2SiPh2H (49.0 mg, 0.134 mmol) at -30 °C, and the resulting
solution was stored in a chilled box at -30 °C overnight. Pentane
(2 mL) was added to the resulting solution. The solution was
allowed to stand for 2 days in the chilled box to afford light yellow
[Pt(PPh3)(µ-SiHPh2)]2 (6a). Method A. To a toluene solution
(3 mL) of 1 (150 mg, 0.200 mmol) was added HSiPh2SiPh2H (73.5
mg, 0.200 mmol) at room temperature, and the mixture was stirred
for 10 min. The resulting solution was allowed to stand for 2 days at
room temperature to afford colorless microcrystals. Yield: 64.7 mg
(51%).
Method B. Complex 4a (10 mg, 0.011 mmol) was dissolved in
toluene-d8 at room temperature. The resulting solution was allowed
to stand overnight at room temperature to afford colorless crystals.
Anal. Calcd for 6a (C60H52P2Pt2Si2): C, 56.24; H, 4.09. Found: C,
56.07; H, 3.87.
1
crystals. Yield: 70.5 mg (45%). H NMR (toluene-d8, 300 MHz,
–30 °C): δ 7.60 (d, 8H, 3JHH ) 6.0 Hz, SiPh), 7.35 (m, 12H, PPh),
2
7.2–7.0 (m, SiPh), 6.9–6.7 (m, 18H, PPh), 5.80 (t, 2H, JPtH ) 71
3
Hz, JPH ) 18 Hz, SiH). 31P{1H} NMR (toluene-d8, 122 MHz,
[Pt(PPh3)(µ-SiHMe2)]2 (6b). Complex 5b (50.2 mg, 0.0388
mmol) was dissolved in toluene/pentane at room temperature. The
resulting solution was allowed to stand for a few days at room
temperature to afford colorless crystals. Yield: 13.9 mg (36%). 1H
NMR (CD2Cl2, 300 MHz, -70 °C): δ 7.56 (br, 12H, PPh), 7.34
1
-30 °C): δ 31.6 (s, JPtP ) 1743 Hz). Anal. Calcd for 3a
(C60H52P2PtSi2): C, 66.34; H, 4.83. Found: C, 66.08; H, 4.59.
[Pt(PPh3)2(SiHMe2)2] (3b). Complex 3b was synthesized by the
same method as that used for 3a, except for HSiMe2SiMe2H. Yield:
110 mg (49%). 1H NMR (toluene-d8, 300 MHz, 0 °C): δ 7.45 (m,
1
2
(br, 18H, PPh), 1.58 (s, 2H, JPtH ) 641 Hz, JPtH ) 131 Hz,
3
Si-H-Pt), 0.22 (s, 12H, SiMe). 31P{1H} NMR (CD2Cl2, 122 MHz,
-70 °C): δ 31.6 (s, JPtP ) 4197 Hz, JPtP ) 311 Hz, JPP ) 62
Hz). Anal. Calcd for 6b · C7H8 (C47H52P2Pt2Si2): C, 50.17; H, 4.66.
Found: C, 51.93; H, 4.82.
12H, PPh), 7.0–6.8 (m, 18H, PPh), 4.42 (ts, 2H, JPH ) 20 Hz,
3JHH ) 3.9 Hz, SiH), 0.72 (d, 12H, 3JPtH ) 29 Hz, 3JHH ) 3.6 Hz,
SiMe). 31P{1H} NMR (toluene-d8, 122 MHz, 0 °C): δ 34.9 (s, 1JPtP
) 1679 Hz). Anal. Calcd for 3b · 0.5C7H8 (C43.5H48P2PtSi2): C,
59.10; H, 5.47. Found: C, 59.45; H, 5.58.
1
2
3
Kinetics. The formation of complex 2a was confirmed by
[Pt(PPh3)2(H)(SiHPh2)] (4a). To a toluene solution (2 mL) of
1 (150 mg, 0.200 mmol) was added a toluene solution (2 mL) of
HSiPh2SiPh2H (73.5 mg, 0.200 mmol) at -30 °C, and the mixture
was stirred at -10 to -5 °C for 1 h. Pentane (2 mL) was added to
the resulting solution. The solution was allowed to stand in a chilled
1
increasing the peak intensity at 7.82 ppm in the H NMR spectra.
A residual protonated solvent at 2.09 ppm in toluene-d8 was used
as an internal standard, and the conversion rate of 2a was estimated
from the area ratio of the peak at 7.82 ppm to that at 2.09 ppm.
The data collection was performed at 5 or 10 min intervals at -40
°C for 90 min (over 3 times the half-life). The data were analyzed
with Igor (WaveMatrics, Inc.) on a Macintosh computer and fitted
to an exponential function by a nonlinear least-squares method.
X-ray Crystallography. Single crystals of 3a, 3b, 4a, 5b, 6a, and
6b suitable for XRD analyses were obtained by allowing their
corresponding toluene/pentane solutions to stand for a few days. Each
crystal was mounted on a glass fiber, and the diffraction data of all
the complexes except 4a were collected on a Bruker-AXS M06XCE
imaging plate using graphite-monochromated Mo KR radiation at 120
K. The diffraction data of 4a were collected on a Bruker-AXS SMART
APEXII. The crystal data and experimental details are listed in Table
1. The number of solvent molecules in the crystal structure of 3a, 4a,
and 5b was determined in the XRD analyses.
box at -30 °C to afford colorless crystals. Yield: 74.3 mg (37%).
1H NMR (toluene-d8, 300 MHz, -30 °C): δ 8.02 (d, 4H, JHH
)
3
6.6 Hz, SiPh), 7.5–7.4 (m, 12H, PPh), 7.25 (t, 4H, 3JHH ) 6.9 Hz,
SiPh), 7.19 (d, 2H, 3JHH ) 7.2 Hz, SiPh), 7.0–6.85 (m, 18H, PPh),
1
2
4.79 (br, 1H, SiH), -1.08 (dd, JPtH ) 1009 Hz, JPH ) 151 Hz
(trans), 17 Hz (cis), PtH). 31P{1H} NMR (toluene-d8, 122 MHz,
1
-30 °C): δ 35.8 (s, JPtP ) 2518 Hz, PPh3 trans to H), 35.2 (s,
1JPtP ) 1768 Hz, PPh3 cis to H). 1H NMR (CD2Cl2, 300 MHz,
-50 °C): δ 7.55–7.4 (m, 4H, SiPh), 7.4–7.0 (m, 36H), 4.00 (ddd,
3
3
1H, JPH ) 21 Hz (trans), 14 Hz (cis), J(Pt)HH ) 2.4 Hz, SiH),
1
2
-1.89 (ddd, JPtH ) 996 Hz, JPH ) 152 Hz (trans), 20 Hz (cis),
3J(Si)HH ) 2.4 Hz, PtH). 31P{1H} NMR (CD2Cl2, 122 MHz, -50
1
2
°C): δ 35.7 (d, JPtP ) 1800 Hz, JPP ) 11 Hz, PPh3 cis to H),
34.5 (d, 1JPtP ) 2477 Hz, 2JPP ) 11 Hz, PPh3 trans to H). IR (KBr,
cm-1): 2037 (PtH), 1956 (SiH). Anal. Calcd for 4a · C7H8
(C55H50P2PtSi): C, 66.32; H, 5.06. Found: C, 66.72; H, 4.96.
[(PPh3)2Pt(H)(µ-SiMe2)(µ-SiHMe2)2Pt(PPh3)] (5b). Method
A. To a toluene solution (2 mL) of 1 (202 mg, 0.271 mmol) was
added HSiMe2SiMe2H (31.8 mg, 0.269 mmol) at room temperature,
and the mixture was allowed to stand overnight. Pentane (4 mL)
was added slowly to the toluene solution, and then the resulting
solution was allowed to stand for 2 days at room temperature to
afford yellow crystals. Yield: 145 mg (83%).
All the structures were solved by the combination of the direct
method and Fourier techniques, and all the non-hydrogen atoms were
anisotropically refined by full-matrix least-squares calculations. The
atomic scattering factors and anomalous dispersion terms were obtained
from the International Tables for X-ray Crystallography IV.26 Since
the numbers of reflection data for the above-mentioned crystals were
insufficient for refining all the parameters of the hydrogen atoms, they
were not included for further refinement; their positions were obtained
from difference Fourier maps. All the calculations were carried out
on a Silicon Graphics workstation by the maXus program.
Method B. Complex 3b (50 mg, 0.060 mmol) was dissolved in
toluene at room temperature. The resulting solution was allowed
to stand for 2 days at room temperature, and then pentane was added
to the solution. 5b crystallized as colorless crystals from a toluene/
pentane solution after allowing the solution to stand for 2 days.
Acknowledgment. We thank Dr. Kenji Yoza of Bruker
AXS K.K. for assisting in the measurement of XRD data of
4b. This work was partly supported by a Grant-in-Aid for
Scientific Research on Priority Areas (No. 19027051, Synergy
of Elements) from the Ministry of Education, Science, Sports,
and Culture of Japan (K.M.), to which our thanks are due.
1
Yield: 20.7 mg (53%). H NMR (CD2Cl2, 300 MHz, -70 °C): δ
7.7–7.5 (m, 12H, PPh), 7.5–6.8 (m, 33H, PPh), 0.70 (d, 1H, JPH
2
) 6.5 Hz, Si-H-Pt), 0.11 (s, 6H, SiMe), -0.43 (s, 6H, SiMe),
-7.05 (t, 1H, 1JPtH ) 553 Hz, 2JPtH ) 86 Hz, 2JPH ) 14 Hz, PtH).
31P{1H} NMR (CD2Cl2, 122 MHz, -70 °C): δ 31.7 (t, JPtP
)
1
1
Supporting Information Available: Selected H and 31P{1H}
4111 Hz, 2JPtP ) 309 Hz, 3JPP ) 29 Hz), 22.4 (d, 1JPtP ) 3704 Hz,
NMR data and kinetics. This material is available free of charge
via the Internet at http://pubs.acs.org.
(26) Ibers, J. A., Hamilton, W. C. International Tables for X-ray
Crystallography; Kynoch Press: Birmingham, U.K., 1974; Vol. IV.
OM800012S