Synthesis and structure of a trinuclear platinum complex with μ3-silylyne ligands derived from a disilane

Article abstract of DOI:10.1021/om900533z

The platinum complex [Pt(dppe)(η²-C₂H ₄)] (1) reacted with the disilane H₂SiMeSiMe₃, affording the bis-(μ-silylyne)triplatinum complex [Pt₃(dppe) ₃(μ₃-SiMe)₂] (4) by a stepwise Si - H and Si - Si bond activation.

Full text of DOI:10.1021/om900533z

Organometallics 2009, 28, 4629–4631 4629
DOI: 10.1021/om900533z
Synthesis and Structure of a Trinuclear Platinum Complex with
μ3-Silylyne Ligands Derived from a Disilane
Hidekazu Arii,† Makiko Takahashi,† Masato Nanjo,†,‡ and Kunio Mochida*,†
†Department of Chemistry, Gakushuin University, 1-5-1 Mejiro, Toshima-ku, Tokyo 171-8588, Japan, and
‡Present address: Department of Chemistry and Biotechnology, Graduate School of Engineering, Tottori
University, Koyama-cho-Minami, Tottori 680-8552, Japan
Received June 19, 2009
Summary: The platinum complex [Pt(dppe)(η2-C2H4)] (1)
reacted with the disilane H2SiMeSiMe3, affording the bis-
(μ-silylyne)triplatinum complex [Pt3(dppe)3(μ3-SiMe)2] (4) by
a stepwise Si-H and Si-Si bond activation.
silylene ligands have been characterized by structural analy-
sis and DFT calculations,4-6 but no silylyne complexes have
yet been reported.
We have investigated the reaction of the zerovalent
platinum complex [Pt(PPh3)2(η2-C2H4)] with symmetric
disilanes HSiR2SiR2H (R = Ph, Me) by NMR spectro-
scopy and X-ray diffraction analysis to characterize the
several platinum complexes formed by Si-H activation,
1,2-migration, and liberation of silylene.7 Multiactivation
of Si-Si and/or Si-H bonds in disilane or oligosilane com-
pounds makes it possible to obtain a multinuclear complex.
We report herein that treatment of [Pt(dppe)(η2-C2H4)] (1)
bearing the bidentate phosphine ligand dppe (=1,2-bis-
(diphenylphosphino)ethane) with the disilane H2SiMe-
SiMe3 produces a triplatinum complex with two μ3-sily-
lyne ligands.
Organosilanes bound to transition-metal centers have
recently attracted the interest of researchers with regard to
their structure and reactivity with various substrates. Both
metal-silylene and metal-silylyne complexes have been
studied in detail, but there are limited reports on the pre-
paration of complexes with metal-silylyne character.1 The
silicon atom in a metal-silylyne complex can bind to a metal
center(s) in a terminal triple-bond fashion2 or a bridging
one.3 Bridging silylyne complexes contain three or more
metal atoms, such as in the triiron complex [Cp3-
Fe3(CO)4SiN(SiMe3)2] (Cp = cyclopentadienyl)3c and the
tetracobalt complex [Co4(μ4-SiMe)2(CO)11].3a Group 10
transition-metal palladium and platinum complexes are
well-known as catalysts for hydrosilylation and double
silylation of unsaturated hydrocarbons. The mono-,
di-, and trinuclear palladium or platinum complexes with
Complex 1 reacted with H2SiMeSiMe3 in toluene at -30 °C
at a molar ratio of 1:1, affording the disilanylplatinum hydride
[Pt(dppe)(H)(SiHMeSiMe3)] (2) by the oxidative addition of
an Si-H bond to the platinum center (eq 1). The Pt-H and
Si-H signals in the 1H NMR spectrum of 2 were observed as a
doublet of doublets with 195Pt satellites at 0.73 ppm (1JPtH
=
2
2
1121 Hz, JPH(trans) = 169 Hz, JPH(cis) = 14 Hz) and a
multiplet at 4.62 ppm, respectively. The Pt-H peaks shifted to
a lower magnetic field compared to that of the silylplatinum
hydrides reported previously (-5 to -1 ppm).7,8 Two phos-
*To whom correspondence should be addressed. Tel: þ81-3-3986-
0221. Fax: þ81-3-5992-1029. E-mail: kunio.mochida@gakushuin.ac.jp.
(1) (a) Waterman, R.; Hayes, P. G.; Tilley, T. D. Acc. Chem. Res.
ꢀ
2007, 40, 712–719. (b) Balazs, G.; Gregoriades, L. J.; Scheer, M. Organo-
1
metallics 2007, 26, 3058–3075.
phine resonances observed at 55.9 (s, JPtP = 2001 Hz) and
1
62.2 ppm (s, JPtP = 1534 Hz) in 2 indicate nonequivalent
phosphine atoms (Figure 1, bottom).
(2) (a) Grumbine, S. D.; Chadha, R. K.; Tilley, T. D. J. Am. Chem.
Soc. 1992, 114, 1518–1520. (b) Mork, B. V.; Tilley, T. D. Angew. Chem.,
Int. Ed. 2003, 42, 357–360.
(3) (a) Anema, S. G.; Lee, S. K.; Mackay, K. M.; Nicholson, B. K. J.
Organomet. Chem. 1993, 444, 211–218. (b) Kawano, Y.; Tobita, H.; Shimoi,
M.; Ogino, H. J. Am. Chem. Soc. 1994, 116, 8575–8581. (c) Hirotsu, M.;
Nishida, T.; Sasaki, H.; Muraoka, T.; Yoshimura, T.; Ueno, K. Organome-
tallics 2007, 26, 2495–2498.
(4) (a) Sharma, H. K.; Pannell, K. H. Chem. Rev. 1995, 95, 1351–
1374. (b) Corey, J. Y.; Braddock-Wilking, J. Chem. Rev. 1999, 99, 175–292.
(5) (a) Chen, W.; Shimada, S.; Hayashi, T.; Tanaka, M. Chem. Lett.
2001, 1096–1097. (b) McGuinness, D. S.; Yates, B. F.; Cavell, K. J.
Organometallics 2002, 21, 5408–5414. (c) Avent, A.; Gehrhus, B.;
Hitchcock, P. B.; Lappert, M. F.; Maciejewski, H. J. Organomet. Chem.
2003, 686, 321–331. (d) Watanabe, C.; Iwamoto, T.; Kabuto, C.; Kira, M.
Angew. Chem., Int. Ed. 2008, 47, 5386–5389. (e) Tanabe, M.; Mawatani, A.;
Osakada, K. Organometallics 2007, 26, 2937–2940.
(6) (a) Heyn, R. H.; Tilley, T. D. J. Am. Chem. Soc. 1992, 114, 1917–
1919. (b) Feldman, J. D.; Mitchll, G. P.; Nolte, J.-O.; Tilley, T. D. J. Am.
Chem. Soc. 1998, 120, 11184–11185. (c) 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. (d) Osakada, K.;
Tanabe, M.; Tanase, T. Angew. Chem., Int. Ed. 2000, 39, 4053–4055.
(e) Braddock-Wilking, J.; Levchinsky, Y.; Rath, N. P. Organometallics 2001,
20, 474–480. (f) Braddock-Wilking, J.; Corey, J. Y.; Trankler, K. A.; Dill, K.
M.; French, L. M.; Rath, N. P. Organometallics 2004, 23, 4576–4584.
(g) Sasaki, S.; Yamaguchi, S.; Musashi, Y.; Sugimoto, M. J. Organomet.
Chem. 2001, 635, 173–186.
Complex 2 was gradually converted into two new pro-
ducts, accompanied by the evolution of Me3SiH gas
at 0 °C, on the basis of 1H NMR spectroscopy (eq 2).
After the complete disappearance of 2, the 1H and
31P{1H} NMR spectra showed the formation of both a
(7) Arii, H.; Takahashi, M.; Noda, A.; Nanjo, M.; Mochida, K.
Organometallics 2008, 27, 1929–1935.
(8) (a) Koizumi, T.; Osakada, K.; Yamamoto, T. Organometallics
1997, 16, 6014–6016. (b) 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. (c) 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.
r
2009 American Chemical Society
Published on Web 07/31/2009
pubs.acs.org/Organometallics

4630 Organometallics, Vol. 28, No. 16, 2009
Arii et al.
Figure 1. 31P{1H} NMR spectra of 2 in toluene-d8 at -30 °C
(bottom) and after 2 days of standing at 0 °C (top).
Figure 2. Crystal structure of 4, showing 50% probability
thermal ellipsoids. The hydrogen atoms are omitted for clarity.
Selected bond lengths (A) and angles (deg): Pt(1)-Si(1) =
Scheme 1
˚
2.3679(14), Pt(1)-Si(2)=2.3726(16), Pt(2)-Si(1)=2.3749(14),
Pt(2)-Si(2) = 2.3740(15), Pt(3)-Si(1) = 2.3838(15), Pt(3)-
Si(2)=2.3831(14), Si(1)-Si(2)=2.642(2); Pt(1)-Si(1)-Pt(2)=
93.03(5), Pt(1)-Si(1)-Pt(3) = 93.38(5), Pt(2)-Si(1)-Pt(3) =
89.87(5), Pt(1)-Si(2)-Pt(2) = 92.93(5), Pt(1)-Si(2)-Pt(3) =
93.28(5), Pt(2)-Si(2)-Pt(3)=89.91(5).
a platinum atom of another molecule of [Pt(dppe)(SiH2Me)-
(SiMe3)], and finally a reductive elimination of SiHMe3 from
the diplatinum complex generates 3. Unfortunately, a pure
sample of 3 could not be obtained due to contamination with
unreacted 2 or simultaneous formation of 4.
bis(μ-silylene)diplatinum complex (3) and a bis(μ3-silyly-
ne)triplatinum complex (4) (Figure 1, top). In previous work,
the reaction of [Pt(PEt3)3] with H2SiMeSiMe3 evolves Me3-
SiH gas, although no platinum complexes with a Pt-Si bond
such as a disilanylplatinum hydride were detected in NMR
spectroscopy.9 Two phosphine resonances at 60.1 and
60.6 ppm in 3 have two sets of 195Pt satellites and correlate
with the two Si-H signals at 6.25 and 6.52 ppm, respectively,
in the 1H-31P HMBC spectrum. These peaks are attributed
to the presence of cis/trans isomers of 3 with respect to the
orientation of the methyl group on the Si atom, and the cis/
trans isomer ratio was roughly 1:3, estimated from the
integral value of the Si-H signals. The silicon resonances
The addition of 1 to a mixture of 3 and 4 resulted only in
the formation of 4, with complete consumption of 3
(Scheme 1). The isolation of 4 was carried out by a reaction
of 1 with H2SiMeSiMe3 at a 3:2 molar ratio in toluene/
pentane at room temperature. The structure of 4 (Figure 2)13
is a trinuclear platinum complex with a pseudo-3-fold axis on
the Si-Si alignment in which the three Pt(dppe) units are
bridged by two SiMe silylynes. The three platinum centers
have a four-coordinate planar geometry and form an equi-
1
of cis- and trans-3 in a H-29Si HMQC experiment were
observed as a single peak at -94 ppm, due to overlap with
each other, and the chemical shift of this peak was diagnostic
of a diplatinum complex with bridging silylenes SiHR, as
reported previously.6c,6e,10 Considering the formation pro-
cess of 3 according to the literature,11,12 at first a 1,2-silyl
migration in 2 could produce a transient (silyl)(silylene)-
platinum hydride, [Pt(dppe)(H)(dSiHMe)(SiMe3)], in which
one end of phosphine dissociates from the platinum atom,
and a 1,2-hydrogen migration from Pt to Si followed by a
phosphine recoordination affords the bis(silyl)platinum
complex [Pt(dppe)(SiH2Me)(SiMe3)]. An oxidative addition
of the Si-H bond in the bis(silyl)platinum complex occurs at
˚
lateral triangle. All Pt-Pt distances are 3.36-3.46 A, indi-
cating that there is no interaction between the platinum
˚
atoms. The Si-Si distance (2.644(2) A) is close to those of
the bis(μ-silylene)diplatinum complexes.6c,6e,10,14 A tetra-
nuclear platinum complex with a triply bridging silylene
containing one Pt
H
Si bond in a nonclassical 3c-2e
interaction has been synthesized by the reaction of
3 3 3 3 3 3
[Pt(PEt3)3] with (n-hexyl)SiH3, where Si-H bond activation
(9) Yamashita, H.; Tanaka, M.; Goto, M. Organometallics 1992, 11,
3227–3232.
(10) Braddock-Wilking, J.; Levchinsky, Y.; Rath, N. P. Inorg. Chim.
(13) Crystal data for 4: C80H78P6Pt3Si2, Mr=1866.69, orthorhombic,
˚
˚
˚
space group Pcab, a=17.3690(2) A, b=19.5120(3) A, c=42.7330(6) A,
3
V=14482.4(3) A , Z=8, Fcalcd=1.712 g cm-3, μ(Mo KR)=5.991 mm-1
,
˚
Acta 2002, 330, 82–88.
117 859 collected reflections, 16 926 crystallographically independent
reflections (Rint=0.064), 14 426 reflections with I > 2σ(I), R1=0.0442
(I > 2σ(I)), wR2=0.1162 (all data).
(11) Mitchell, G. P.; Tilley, T. D. Angew. Chem., Int. Ed. 1998, 37,
2524–2526.
(12) Shimada, S.; Rao, M. L. N.; Li, Y.-H.; Tanaka, M. Organome-
(14) Zarate, E. A.; Tessier-Youngs, C. A.; Youngs, W. J. J. Am.
tallics 2005, 24, 6029–6036.
Chem. Soc. 1988, 110, 4068–4070.

Communication
Organometallics, Vol. 28, No. 16, 2009 4631
of the μ-silylene Si(H)(n-Hexyl) does not occur.6c Complex 4
is a rare example of a platinum complex with a bridging
some zerovalent platinum species are likely to be produced,
since the formation of [Pt(dppe)2] was confirmed by the
1
silylyne. The simple H NMR spectrum of 4 is consistent
with a structure with a pseudo-3-fold axis, and the absence of
observation of the characteristic peak at 30.9 ppm (1JPtP
=
3727 Hz)15 in the 31P NMR spectrum during the conversion
of 3 to 4.
1
Pt-H and Si-H signals in the H NMR and IR spectra
indicates that there are no hydrides present in 4. The broad-
ness of the Si-Me peak at 0.58 ppm is independent of a
temperature change from -70 to 50 °C and is related to the
coupling to phosphine and platinum nuclei. The 31P{1H}
NMR spectrum showed a singlet at 33.0 ppm with two or
more sets of satellites associated with a multinuclear plati-
num complex. A silicon resonance of 4 at 42.2 ppm in a
1H-29Si HMBC experiment showed a remarkable downfield
shift as compared to that of the bis(μ-silylene)diplatinum
complexes, which implies that the Pt-Si bonds of 4 have a
character similar to that of a Pt-Si single bond. It was
unclear how 4 could be generated in a toluene solution of 3
in the absence of a zerovalent platinum species. However,
In summary, a stepwise Si-H and Si-Si bond activation
affords a unique triplatinum complex with two bridging
silylyne ligands in moderate yield through the use of H2Si-
MeSiMe3.
Acknowledgment. This work was financially supported
by a grant from the Iketani Science and Technology
Foundation (H.A.) and a Grant-in-Aid for Scientific
Research from the Ministry of Education, Science,
Sports, and Culture of Japan (K.M.).
Supporting Information Available: Text and figures giving
details of the syntheses and selected NMR data of 2-4
and a CIF file giving crystallographic data for 4. This
material is available free of charge via the Internet at http://
pubs.acs.org.
(15) Clark, H. C.; Kapoor, P. N.; McMahon, I. J. J. Organomet.
Chem. 1984, 265, 107–115.