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Me, 3b: R = Et) show a singlet with 195Pt satellites in the
of [Pt(PEt3)3] with an excess of HSi(OEt)3 affords the
isomeric compounds cis-[Pt(H){Si(OEt)3}(PEt3)2] and trans-
[Pt(H){Si(OEt)3}(PEt3)2].[16] Reaction of an excess of HSiPh3
with [Pt(PCy3)2] yields cis-[Pt(H)(SiPh3)(PCy3)2].[18] The gen-
eration of Si(OR)4 was confirmed by 29Si{1H} and 1H–29Si
HMBC NMR spectroscopy (R = Me: d = À79 ppm; R = Et:
d = À82 ppm). The 31P{1H} NMR spectrum for 4 shows
a singlet with 195Pt satellites at d = 76.8 ppm (1J(P,Pt) =
1690 Hz). The SiH3 group gives rise to a virtual triplet in
the 1H NMR spectrum at d = 4.12 ppm (1J(H,P) = 6.9 Hz)
with 29Si satellites and 195Pt satellites. The triplet transforms
into a singlet with satellites upon phosphorus decoupling. The
hydrogen–platinum coupling constant is 30 Hz and the
hydrogen–silicium coupling constant is 166 Hz. The coupling
constants are similar to those found for complex
[Pt(H)(SiH3)(PCy3)2], which was synthesized by reaction of
trans-[Pt(H)2(PCy3)2] with SiH4.[19] The 29Si{1H} NMR spec-
trum for 4 shows a doublet of doublets at d = À72.4 ppm with
195Pt satellites that are due to couplings to phosphorus atoms
in the cis and trans position. Without hydrogen decoupling,
the signal appears as an apparent quintet, which is the result
of comparable silicon–hydrogen and silicon–phosphorus
coupling constants. These signals are in accordance with the
cross-peaks found in the 1H–29Si HMBC NMR spectrum.
The molecular structure of 4 was determined by X-ray
diffraction analyses (Figure 1).[20] Suitable crystals were
obtained from a toluene/pentane solution at 278 K. Complex
4 shows a distorted square-planar arrangement of the chelat-
ing phosphine ligand and the two silyl ligands at the platinum
center. The silicon-bound hydrogen atoms were located in the
difference Fourier map and were refined isotropically. The
1
31P{1H} NMR spectra (3a: 76.4 ppm, J(P,Pt) = 1496 Hz; 3b:
75.3 ppm, 1J(P,Pt) = 1499 Hz). The 29Si{1H} NMR spectra
displays a doublet of doublets with 195Pt satellites (3a:
5.52 ppm, 1J(Si,Pt) = 1902 Hz; 3b: 2.94 ppm, 1J(Si,Pt) =
1918 Hz) for the two silyl ligands. The coupling constants to
the phosphorus atoms in the cis and trans position are 14 Hz
and 228 Hz.
The NMR data of the hydrido silyl complexes 2a and 2b
are very similar. The hydrido ligand of 2b gives rise to
a doublet of doublets with 195Pt satellites in the 1H NMR
2
spectrum at d = À1.26 ppm (1J(H,Pt) = 968 Hz, J(H,P-trans)
2
= 153 Hz, J(H,P-cis) = 12 Hz). The 31P{1H} NMR spectrum
shows two doublets with 195Pt satellites for the two inequiva-
lent phosphorus atoms at d = 84.2 ppm (1J(P,Pt) = 1645 Hz,
2J(P,P) = 2.9 Hz) and at d = 74.2 ppm (1J(P,Pt) = 1960 Hz,
2J(P,P) = 2.9 Hz). Because of the strong trans influence of
the silyl group,[13] the 1J(P,Pt) coupling constant for the
phosphorus atom in the trans position to the silyl ligand
(1645 Hz) is smaller than that for the phosphorus atom in the
cis position (1960 Hz). A selective decoupling experiment
2
revealed a J(P,H-trans) coupling constant of 153 Hz for the
signal at d = 74.2 ppm, which can therefore assigned to the
phosphorus atom in the trans position to the hydrido ligand.
1
The H–29Si HMBC NMR spectrum for 2b displays a reso-
nance at d = 12.9 ppm in the 29Si domain, which correlates
with resonances for the Si(OEt)3 group and for the hydrido
ligand.
Apparently, the hydrido silyl complexes 2a and 2b are
generated by reaction of Si2(OR)6 with the dihydrido complex
1 with a concomitant elimination of the tertiary silane
HSi(OR)3. A subsequent reaction of 2a and 2b with disilane
or with the hydrosilane results in the formation of the
bis(silyl) complexes 3a and 3b as well as the elimination of
À
Pt Si bond lengths of 2.3500(7) ꢀ and 2.3408(6) ꢀ are
slightly shorter than that in the platinum complex trans-
[Pt(H)(SiH3)(PCy3)2] (2.382(3) ꢀ).[19] The platinum–phos-
phorus bond is slightly longer (2.3045(5) ꢀ and 2.3075(6) ꢀ)
compared to the distances in trans-[Pt(H)(SiH3)(PCy3)2]
(2.280(2) ꢀ and 2.283(2) ꢀ).[19]
À
HSi(OR)3 or dihydrogen, respectively. Thus, a Si Si activa-
tion of Si2(OMe)6 and Si2(OEt)6 could be achieved. The
generation of HSi(OR)3 and H2 was confirmed by NMR
spectroscopy and GC/MS meassurements. An independent
reaction of 2b with hexamethoxydisilane yielded the complex
3a. Note that a hydrogenolysis of disilanes with dihydrogen is
rarely investigated; most of the conversions involve rather
harsh conditions.[14,15] The hydrogenolysis of Si2(OEt)6 was
described recently at [Pt(PEt3)3]. A reaction in the presence
of dihydrogen yielded cis-[Pt(H){Si(OEt)3}(PEt3)2] and trans-
[Pt(H){Si(OEt)3}(PEt3)2] as well as HSi(OEt)3.[16]
Addition of two equivalents of trimethoxysilane or
triethoxysilane to [Pt(H)2(dcpe)] (1) also afforded the com-
plexes 3a or 3b, respectively (Scheme 1). Again, 2a or 2b
could be detected as intermediates by NMR spectroscopy.
Note that Schubert et al. reported the generation of
[Pt{Si(OMe)3}2{k2-(P,N)-Ph2PCH2CH2NMe2}] by reaction of
[PtMe2{k2-(P,N)-Ph2PCH2CH2NMe2}]
with
trimethoxy-
silane.[17] As an intermediate, a methyl silyl complex was
identified.
Figure 1. An ORTEP diagram of 4. Ellipsoids are set at 50% proba-
bility; hydrogen atoms at the dcpe ligand are omitted for clarity.
Selected bond lengths [ꢁ] and angles [8]: Si1–Pt1 2.3500(7), Si2–Pt1
2.3408(6), P1–Pt1 2.3045(5), P2–Pt1 2.3075(6); P1-Pt1-P2 86.992(19),
P1-Pt1-Si1 95.38(2), P1-Pt1-Si2 178.45(2), P2-Pt1-Si1 176.31(2), P2-Pt1-
Si2 94.54(2), Si2-Pt1-Si1 83.10(2).
In a remarkable conversion, complex 1 reacts with an
excess of HSi(OMe)3 or HSi(OEt)3 to give solely the bis(silyl)
complex [Pt(SiH3)2(dcpe)] (4) and Si(OR)4 (Scheme 1). This
À
observation is in contrast to activation reactions of Si H
bonds at platinum(0) complexes.[16,18] For instance, treatment
ꢀ 2013 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Angew. Chem. Int. Ed. 2013, 52, 8625 –8628