Reaction of 1-(dimethylsilyl)-2-silylbenzene with platinum(0) phosphine complex: Isolation and characterization of the Si3-PtIV-H complex

Article abstract of DOI:10.1016/j.jorganchem.2010.05.023

Reaction of two equivalents of 1,2-C₆H₄(SiMe ₂H)(SiH₃) with Pt(depe)(PEt₃)₂ (depe = Et₂PCH₂CH₂PEt₂) in toluene at room temperature afforded two n

Full text of DOI:10.1016/j.jorganchem.2010.05.023

Journal of Organometallic Chemistry 695 (2010) 2057e2061
Contents lists available at ScienceDirect
Journal of Organometallic Chemistry
journal homepage: www.elsevier.com/locate/jorganchem
Communication
Reaction of 1-(dimethylsilyl)-2-silylbenzene with platinum(0) phosphine
complex: Isolation and characterization of the Si3ePtIVeH complex
,
a
b
Yong-Hua Li a , Yuan Zhang , Shigeru Shimada
*
a College of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, People’s Republic of China
b Research Institute for Innovation in Sustainable Chemistry, National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi, Tsukuba,
Ibaraki 305-8565, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Reaction of two equivalents of 1,2-C6H4(SiMe2H)(SiH3) with Pt(depe)(PEt3)2 (depe ¼ Et2PCH2CH2PEt2) in
toluene at room temperature afforded two novel isomeric {1,2-C6H4 -(SiMe2H)(SiH2)}{1,2-C6H4(SiMe2)
(SiH2)}(H)PtIV (depe) complexes 1 and 2 in 5:1 ratio among eight possible isomers. Complex 1 is one of
the few examples of tris(silyl)(hydrido)platinum(IV) complexes structurally characterized by single
crystal X-ray analysis. The structure of complex 1 was unambiguously determined by multinuclear NMR
and single crystal X-ray analysis.
Received 22 April 2010
Received in revised form
19 May 2010
Accepted 21 May 2010
Available online 2 June 2010
Ó 2010 Elsevier B.V. All rights reserved.
Keywords:
Isomeric complexes
Dehydrogenative cyclization
Multinuclear NMR
Platinum
1. Introduction
(hydrido)platinum(II) or bis(silyl)-platinum(II) complexes [2],
while that with primary and secondary hydrosilanes affords
Since the first complex containing SieM bond was synthesized
by Wilkinson and co-workers in 1956, the chemistry of transition
metal complexes with metal-silicon bonds has rapidly grown
during the last two decades and the pace of progress is still
increasing, associated mainly with catalysis involving silicon
compounds toward organic synthesis and silicon-based materials
[1]. As compared with CeH bonds, SieH bonds have higher reac-
tivity toward transition metals, one of the most effective methods
for the preparation of these complexes is by the reactions of tran-
sition metal complexes with hydrosilanes via SieH activation [1,2].
Furthermore, activation of SieH bonds is also very important in
industrial processes such as hydrosilylation, dehydrogenative sily-
lation, and polysilane production [1,3]. It is widely considered that
oxidative addition of the SieH bond to a metal centre is one of the
crucial steps in these processes [1e4].
The reaction chemistry of transition metal complexes with
primary and secondary hydrosilanes (RSiH3 and R2SiH2) has been
rapidly growing recently. It is often different from that with tertiary
hydrosilanes (R3SiH) because primary and secondary hydrosilanes
have more than one reactive SieH bond and/or are sterically less
hindered than tertiary hydrosilanes [2]. The reaction of Pt(0)
complexes with tertiary hydrosilanes usually produces (silyl)
various types of platinum complexes with mononuclear [2], dinu-
clear [2,5], or trinuclear frameworks [6].
Our present research focus on the preparation of silicone
transition metal complexes with various numbers of SieM bonds,
especially those with high oxidation states [7]. During our attempt
to synthesize poly(silyl) group 10 transition metal compounds, we
have found that sterically less-demanding chelating silyl ligands
are very useful to stabilize silyl transition metal compounds with
high formal oxidation states and reported the first examples of
multinuclear palladium compound containing palladium centers
ligated by five silicon atoms [8].
Here we report the reaction of a bidentate chelating hydrosilane
with platinum(0) complex, resulting in the isolation of mono-
nuclear tris(silyl)(hydrido)platinum(IV) complex 1. To our knowl-
edge, there are only more than 5 examples of tris(silyl)(hydrido)
platinum(IV) complexes structurally characterized by single crystal
X-ray analysis [9].
2. Experimental
2.1. Materials and equipment
1H, 29Si, and 31P NMR spectra were recorded on JEOL LA500 (for
solution NMR). Chemical shifts are given in ppm using external
* Corresponding author. Fax: þ86 25 83335707.
E-mail address: liyhnju@hotmail.com (Y.-H. Li).
0022-328X/$ e see front matter Ó 2010 Elsevier B.V. All rights reserved.
doi:10.1016/j.jorganchem.2010.05.023

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Y.-H. Li et al. / Journal of Organometallic Chemistry 695 (2010) 2057e2061
references (for solution NMR spectra, tetramethylsilane (0 ppm) for
1H and 29Si and 85% H3PO4 (0 ppm) for 31P), and coupling constants
are reported in hertz. C, H and N analyses were taken on a Per-
kineElmer 240C elemental analyzer. All reagents and solvents were
of reagent-grade quality obtained from commercial suppliers. All
solvents were dried and purified. The solvents were stored over
GC-MS analysis of the mixture at this stage showed the presence of
partially reduced products. Then, LiAlH4 (1.5 g) was added and the
mixture was refluxed for another 13 h. After removal of ether under
reduced pressure, the remaining mixture was extracted with
hexane (250 mL*3), and then filtered through Celite. Hexane was
removed under reduced pressure, the product was transferred to
a cold flask under high vacuum. Purification by distillation gave
9.6 g of 1-(dimethyl)-2-silylbenzene, 134 ꢀC/50 Torr, as colorless
ꢀ
molecular sieves (4 A).
liquid. 1H NMR (CDCl3, 300 MHz)
d 0.39 (6H, d), 4.32 (3H, s), 4.66
2.2. Syntheses
(1H, septet), 7.35e7.45 (1H, m), 7.32e7.45 (1H, m), 7.59 (1H, dd),
7.68 (1H, dd); 13C NMR (CDCl3, 300 MHz)
134.22, 135.40, 137.51, 138.24.
d
ꢁ3.27, 128.57, 129.29,
2.2.1. Preparation of 1-(dimethyl)-2-silylbenzene
To a solution of phenyltris(N,N,N0-trimethylethylenediamino)-
silane (48 g) in hexane (250 mL) was added a pentane solution of
tBuLi (1.53 M, 217 mL) over 40 min at 0 degree under nitrogen. After
stirring at room temperature for 3 h, the solution was added by
using a polyethylene tube to a solution of Me2SiCl2 (195 g) in
hexane (120 mL) at 0 degree over 40 min. After the addition was
completed, the mixture was allowed to warm to room temperature
and then heated at 50 degree for about 4 h. Most of the solvents and
excess of Me2SiCl2 were removed under reduced pressure at room
temperature. After the addition of Me2SiCl2 (20 mL) to the residue,
iPrOH (300 mL) was added dropwise at 0 degree. The mixture was
stirred at room temperature for 12 h. Volatiles were removed under
vacuum, hexane (600 mL) was added, and the mixture was filtered
through Celite. The filtrate was further filtered through a short pad
of SiO2 (50 g) to remove the remaining salt. After evaporation, the
residue was subjected to bulb-to-bulb distillation to give 34 g
(75%) of 1-dimethyl(isopropoxy)silyl-2-(triisopropoxysilyl)benzene
(oven temperature 150 ꢀC/1 mmHg). 1H NMR (CDCl3, 300 MHz)
2.2.2. Preparation of {1,2-C6H4-(SiMe2H)(SiH2)}{1,2-C6H4(SiMe2)
(SiH2)}(H)PtIV (depe)complexes (1 and 2)
A mixture of Pt(PEt3)4 (216 mg, 0.32 mmol) and depe (66 mg,
0.32 mmol) in toluene (4 mL) was stirred at room temperature for
40 min to give Pt(PEt3)2(depe). After removal of volatiles under
vacuum, the residual was dissolved in toluene (4 mL). To this
solution was added hydrosilane (117 mg, 0.70 mmol) at 0 ꢀC, and
the mixture was stirred at room temperature for 24 h. Removal of
volatiles under vacuum afforded a light yellow residue, which was
washed with hexane (2 mL*3) and dried under vacuum to give
a mixture of 1 and 2 (5:1 judged by 1H NMR integration) as
a
colorless solid, 155 mg (76%). 31P{1H} NMR (benzene-d6,
202.0 MHz): for 1,
d
5.89 (d, 2JPeP ¼ 8, 1JPteP ¼ 974), 0.67 (d, 2JPeP ¼ 8,
1JPteP ¼ 1436); for 2,
d
16.25 (d, JPeP ¼ 17, JPteP ¼ 1035), 15.97
2
1
(d, JPeP ¼ 17, JPteP ¼ 1115). 1H NMR (benzene-d6, 499.1 MHz):
2
1
2
1
d
ꢁ10.24 (br d, JPeH ¼ 180, JPteH ¼ 862, PteH for 1), ꢁ8.50
(t, 2JPeH ¼ 19, 1JPteH ¼ 796, PteH for 2), 0.41 (dd, J ¼ 4,16, CH3 ꢂ 2 for
2), 0.59 (dd, J ¼ 4, 17, CH3 ꢂ 2 for 1), 0.78e1.27 (m, CH3 ꢂ 2,
(PCH2CH3) ꢂ 4 and PCH2CH2P for 1 and 2), 4.34e5.35 (m, SiH2 ꢂ 2
for 1 and 2), 7.17e7.24 (m, aromatic-H ꢂ 3 for 1 and 2), 7.32 (t, J ¼ 8,
aromatic-H ꢂ 1 for 1), 7.42 (t, J ¼ 7, aromatic-H ꢂ 1 for 2), 7.61e7.70
(m, aromatic-H ꢂ 2 for 1 and 2), 8.08 (d, J ¼ 7, aromatic-H ꢂ 1 for 2),
d
0.51 (6H, s), 1.23 (18H, d), 1.26 (6H, d), 4.11 (1H, septet), 4.26 (3H,
septet), 7.35e7.45 (2H, m), 7.82e7.85 (1H, m), 7.97e8.05 (1H, m).
To an ether suspension (100 mL) of LiAlH4 (10 g) was added
dropwise a solution of 1-dimethyl(isopropoxy)silyl-2-(triisopro-
poxysilyl)benzene (34 g) in ether 80 mL at 0 ꢀC over 40 min. The
mixture was stirred for 5 h at room temperature and 7 h at reflux.
Scheme 1. The reaction of two equivalents of 1,2-C6H4(SiMe2H)(SiH3) with Pt(depe)(PEt3)2 (depe ¼ Et2PCH2CH2PEt2).

Y.-H. Li et al. / Journal of Organometallic Chemistry 695 (2010) 2057e2061
2059
Table 1
Crystal data of compound 1.
8.12e8.14 (m, aromatic-H ꢂ 1 for 1), 8.36 (d, J ¼ 8, aromatic-H ꢂ 1
for 1), 8.81 (d, J ¼ 7, aromatic-H ꢂ 1 for 2). 29Si{1H} NMR (benzene-
2
1
d6, 99.1 MHz): for 1,
d
ꢁ49.8 (dd, JPeSi ¼ 12, 17, JPteSi ¼ 693,
1 2
Structure parameters
Empirical formula
fw
Cryst syst
Space group
Cryst size (mm)
a (Å)
1
2
C26H50P2PtSi4
732.04
Monoclinic
P21/n
SiH2), ꢁ33.6 (t, JPeSi ¼ 13, JPteSi ¼ 599, SiH2), 7.2 (dd, JPeSi ¼ 7,
1
4
138, JPteSi ¼ 645, SiMe2Pt) ¼ ꢁ19.2 (s, JPteSi ¼ 6, SiMe2H); for 2,
2
1
d
ꢁ35.6 (dd, JPeSi ¼ 16, 152, JPteSi ¼ 753, SiH2), ꢁ26.6 (t,
2JPeSi ¼ 10, 1JPteSi ¼ 666, SiH2), 5.7 (dd, 2JPeSi ¼ 10, 147, 1JPteSi ¼ 674,
0.10 ꢂ 0.12 ꢂ 0.13
18.035 (4)
9.921 (2)
18.529 (4)
103.51 (3)
3223.6 (13)
4
293 (2)
1480
1.508
4.615
4
SiMe2Pt), ꢁ19.0 (s, JPteSi ¼ 7, SiMe2H).
b (Å)
c (Å)
b
V (Å3)
Z
3. Results and discussion
(ꢀ)
The reaction of 1,2-C6H4(SiMe2H)(SiH3) and Pt(depe)(PEt3)2
T (K)
(depe ¼ Et2PCH2CH2PEt2) in 2:1 ratio in toluene at room tempera-
F(000)
ture
afforded
tris(silyl)(hydrido)bis-(phosphine)platinum(IV)
rcalc (g cmꢁ3
)
(mmꢁ1
range (deg)
)
complexes as a mixture of two isomers 1 and 2 in 5:1 ratio
(Scheme 1). Crystallization of the mixture from toluene afforded
X-ray quality single crystals only for the major isomer 1, and its
structure was unambiguously confirmed by single crystal X-ray
structure analysis (Fig. 1) [10,11]. Complex 1 crystallizes in the
monoclinic group P21/n (Table 1). The coordination geometry of the
Pt atom is completed by two chelate P atoms, two chelate Si atoms
and one Si atom from one free hydrosilane ligand. The central Pt
atom forms (Si)3(H)PtIV which attained a distorted square-bipyra-
midal geometry with a Si1ePteSi3 angle of 168.1 degree. The
average bond lengths PteSi (2.39 A) and PteP (2.35 A) are in good
agreement with the reported similar complexes [7,9]. The hydrido
ligand occupies the equatorial coordination site. The apical PteSi
bond distance is almost the same as that of equatorial PteSi bond
(Table 2).
m
q
1.8e26.00
20762
6334
Total no. of data collected
No. of unique data
R indexes [I > 2
s(I)]
R1 ¼ 0.0273
wR2 ¼ 0.0409
R (all data)
R1 ¼ 0.0403
wR2 ¼ 0.0418
Largest diff map hole and peak (e Åꢁ3
)
1.02 and ꢁ1.07
P
P
P
P
R1
¼
jjFoj ꢁ jFcjj= jFoj; wR2 ¼ ½ wðFo2 ꢁ Fc2Þ2= wðFo2Þ2ꢃ1=2
:
ꢀ
ꢀ
group in both isomers; a signal for the silicon atom with one
directly connected hydrogen (a broad doublet in the 29Si NMR
spectrum, 1JHeSi ¼ ca. 190 Hz) was, respectively, observed
at ꢁ19.2 ppm (JPteSi ¼ 6 Hz) for the major isomer and at ꢁ19.0 ppm
(JPteSi ¼ 7 Hz) for the minor isomer in the 29Si{1H} NMR spectrum.
The small JPteSi values suggest no direct interaction between these
Si atoms and Pt atoms. From these NMR data, the structures of the
major isomer 1 and the minor isomer 2 can be assigned as shown in
Scheme 1. Signals for SiH2 groups in the 29Si{1H} NMR spectrum are
also consistent with these assignment; the major isomer showed
two SiH2 signals (a triplet and a doublet of doublets) with small
2JPeSi values (12e17 Hz), suggesting that both of the SiH2 groups are
in cis-position relative to both of the P atoms. On the other hand,
the minor isomer also showed a triplet and a doublet of doublets
signals for SiH22groups, one of which had a large (152 Hz) and
The structure of complex 1 was also well identified by elemental
analysis and multinuclear NMR [12]. The 31P{1H} NMR spectrum in
1
C6D6 showed a pair of doublets with relatively small JPteP values
1
typical for silylplatinum(IV) species [13]; JPteP ¼ 974 and 1436 Hz
1
for the major isomer and JPteP ¼ 1035 and 1115 Hz for the minor
isomer. PeH signals in the 1H NMR spectrum are a broad doublet
(2JPeH ¼ 180 Hz) for the major isomer and a triplet (2JPeH ¼ 19 Hz)
for the minor isomer. This suggests that one P atom is trans and the
other P atom is cis to the hydrido ligand in the major isomer and
both P atoms are cis to the hydrido ligand in the minor isomer. The
Me2SiPt signal in each isomer appeared as a doublet of doublets
2
with a large and a small JPeSi value, indicating the Me2Si groups
have one cis and one trans P atom in both isomers. 29Si{1H} and 29Si
NMR spectra clearly showed the presence of an unreacted SiMe2H
2
a small (16 Hz) JPeSi value and the other had small JPeSi values
(10 Hz), suggesting that one of the SiH2 groups is in cis-position
relative to one P atom and in trans-position relative to the other P
atom, while the other SiH2 group is in cis-position relative to both
of the P atoms. Judging from the 31P{1H} NMR spectrum of the
reaction mixture, which showed some unidentified signals with
very weak intensity, the amount of other six isomers (e.g., see 3 and
4 in Fig. 2) is very low even if they are present. Selective formation
of the two isomers 1 and 2 can be mainly attributed to the steric
repulsion caused by methyl groups on silicon and ethyl groups on
Table 2
Selected bond lengths and angles for 1.
Pt1eSi1
Pt1eSi3
Pt1eP2
Si2eC6
Si1ePt1eSi2
Si2ePt1eSi3
Si1ePt1eP1
Si3ePt1eP1
Si2ePt1eP2
Si3ePt1eH1
Si1ePt1eH1
2.3976 (14)
2.4067 (13)
2.3344 (11)
1.896 (4)
83.71 (5)
86.75 (5)
90.68 (5)
97.86 (5)
102.22 (5)
81.00
Pt1eSi2
Pt1eP1
Si1eC1
Si3eC9
Si1ePt1eSi3
P1ePt1eP2
Si2ePt1eP1
Si1ePt1eP2
Si3ePt1eP2
P2ePt1eH1
P1ePt1eH1
2.3896 (11)
2.3584 (11)
1.887 (4)
1.891 (4)
168.05 (5)
85.28 (5)
171.08 (5)
96.71 (5)
92.33 (5)
173.23
Fig. 1. The structure of 1, showing the coordination environment of Pt atom and the
hydrogen atoms bound to carbon atoms are omitted for clarity.
89.75
96.73

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Y.-H. Li et al. / Journal of Organometallic Chemistry 695 (2010) 2057e2061
Fig. 2. Schematic drawings showing steric repulsions between methyl and ethyl groups in complexes 1, 3a and 4a.
phosphorus atoms. Analysis of molecular structures of complexes 1
determined by X-ray diffraction suggests that severe steric repul-
sion is present between some of the methyl groups on silicon and
methyl groups on phosphorus atoms in complexes 1e4. Such steric
repulsion is found between one pair of methyl and ethyl groups in
complexes 1 and 2 (e.g., see 1 in Fig. 2), while between two pairs of
methyl and ethyl groups in complexes 3 (e.g., see 3a in Fig. 2) and
between three or four pairs of methyl and ethyl groups in
complexes 4 (e.g., see 4a in Fig. 2). Heating the mixture of 1 and 2
even after 7 days at 100 ꢀC in toluene could not result in slow
intramolecular dehydrogenative cyclization to afford a mixture of
isomeric {1,2-C6H4(SiMe2)(SiH2)}2PtIV(depe) 5 and 6, probably due
to the steric effect caused by the ethyl groups on phosphorus atoms.
Appendix A. Supplementary material
CCDC-764201 contains the supplementary crystallographic data
for compound 1. These data can be obtained free of charge from the
Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/
data_request/cif.
Supplementary material associated with this article can be found
in the online version, at doi: 10.1016/j.jorganchem.2010.05.023.
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funding from SEU (Grant no. 4007041028, 9207040014 and
9207040013).

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mixture of 1 and 2) Calcd. for C26H50P2PtSi4: C, 42.66; H, 6.88. Found: C,
42.82; H, 6.85. 31P{1H} NMR (benzene-d6, 202.0 MHz): for 1,
d
d
5.89
16.25
2
1
2
1
(d, JPeP ¼ 8, JPteP ¼ 974), 0.67 (d, JPeP ¼ 8, JPteP ¼ 1436); for 2,
(d, JPeP ¼ 17, JPteP ¼ 1035), 15.97 (d, JPeP ¼ 17, JPteP ¼ 1115). 1H NMR
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(benzene-d6, 499.1 MHz):
d
ꢁ10.24 (br d, JPeH ¼ 180, JPteH ¼ 862, PteH for
2
1
1), ꢁ8.50 (t, JPeH ¼ 19, JPteH ¼ 796, PteH for 2), 0.41 (dd, J ¼ 4, 16, CH3 ꢂ 2
for 2), 0.59 (dd, J ¼ 4, 17, CH3 ꢂ 2 for 1), 0.78e1.27 (m, CH3 ꢂ 2,
(PCH2CH3) ꢂ 4 and PCH2CH2P for 1 and 2), 4.34e5.35 (m, SiH2 ꢂ 2 for 1 and
2), 7.17e7.24 (m, aromatic-H ꢂ 3 for 1 and 2), 7.32 (t, J ¼ 8, aromatic-H ꢂ 1
for 1), 7.42 (t, J ¼ 7, aromatic-H ꢂ 1 for 2), 7.61e7.70 (m, aromatic-H ꢂ 2 for
1 and 2), 8.08 (d, J ¼ 7, aromatic-H ꢂ 1 for 2), 8.12e8.14 (m, aromatic-H ꢂ 1
[7] (a) S. Shimada, Y.H. Li, M.L.N. Rao, M. Tanaka, Organometallics 25 (2006)
3796e3798;
(b) S. Shimada, M.L.N. Rao, Y.H. Li, M. Tanaka, Organometallics 24 (2005)
6029e6036.
for 1), 8.36 (d, J ¼ 8, aromatic-H ꢂ 1 for 1), 8.81 (d, J ¼ 7, aromatic-H ꢂ 1 for
2
[8] S. Shimada, Y.H. Li, Y.K. Choe, M. Tanaka, M. Bao, T. Uchimaru, Multinuclear
palladium compounds containing palladium centers ligated by five silicon
atoms. In: Proceedings of the National Academy of Sciences of the United
States of America (PNAS), vol. 104, 2007, pp. 7758e7763.
[9] R.H. Heyn, T.D. Tilley, J. Am. Chem. Soc. 114 (1992) 1917e1919.
[10] Crystal data for 1: M ¼ 732.04, Monoclinic, P21/n, a ¼ 18.035(4) Å, b ¼ 9.921
2). 29Si{1H} NMR (benzene-d6, 99.1 MHz): for 1,
d
ꢁ49.8 (dd, JPeSi ¼ 12, 17,
1JPteSi ¼ 693, SiH2), ꢁ33.6 (t, JPeSi ¼ 13, JPteSi ¼ 599, SiH2), 7.2 (dd,
2
1
2JPeSi ¼ 7, 138, JPteSi ¼ 645, SiMe2Pt) ¼ ꢁ19.2 (s, JPteSi ¼ 6, SiMe2H); for 2,
1
4
2
1
2
d
ꢁ35.6 (dd, JPeSi ¼ 16, 152, JPteSi ¼ 753, SiH2), ꢁ26.6 (t, JPeSi ¼ 10,
2 1
1JPteSi ¼ 666, SiH2), 5.7 (dd, JPeSi ¼ 10, 147, JPteSi ¼ 674, SiMe2Pt), ꢁ19.0
4
(s, JPteSi ¼ 7, SiMe2H).
(2) Å, c ¼ 18.529(4) Å,
a
¼ 90.000ꢀ,
b
¼ 103.510(3)ꢀ,
g
¼ 90.000ꢀ, V ¼ 3223.6
[13] (a) S.L. Grundy, R.D. Holmessmith, S.R. Stobart, M.A. Williams, Inorg. Chem. 30
(1991) 3333e3337;
(3) Å3, Z ¼ 4, F(000) ¼ 1480, R1 ¼ 0.0273, wR2 ¼ 0.0418 [I > 2
s(I)]. Structural
data for was collected on
a
Bruker Smart Apex CCD with graphite-
(b) S. Shimada, M. Tanaka, K. Honda, J. Am. Chem. Soc. 117 (1995) 8289e8290.