Reaction of a Stable Silylene with Divalent Group 14 Compounds

Article abstract of DOI:10.1002/(SICI)1099-0682(199808)1998:8<1067::AID-EJIC1067>3.0.CO;2-7

The reaction of the stable silylene 1 (L′Si:) with CO, SnCl₂, PbCl₂, the stable carbene L′C: (2) and the stable germylene L′Ge: (3) was investigated as a possible approach for the synthesis of hetero-polysilanes (poly-carbosilanes, p

Full text of DOI:10.1002/(SICI)1099-0682(199808)1998:8<1067::AID-EJIC1067>3.0.CO;2-7

FULL PAPER
Synthesis and Reactivity of Low-Coordinate Compounds, 7[᭛]
Ƞ
Reaction of a Stable Silylene with Divalent Group 14 Compounds
Michael K. Denk*, Ken Hatano, and Alan J. Lough
Department of Chemistry, University of Toronto,
Mississauga, Ontario L5L 1C6, Canada
Fax: (internat.) 001-905-828-5335
E-mail: mdenk@credit.erin.utoronto.ca
Internet: http://mdenk.erin.utoronto.ca
Received March 20, 1998
Keywords: Silylene / N Heterocycles / Carbene analogs / Tin / Subvalent compounds
The reaction of the stable silylene 1 (LЈSi:) with CO, SnCl
PbCl , the stable carbene LЈC: (2) and the stable germylene
LЈGe: (3) was investigated as a possible approach for the
2
,
1
Pca2 . The bond angles of 115.89 ° (ave. Si–Sn–Si) and 101.87
° (ave. Cl–Sn–Si) show a slightly flattened tetrahedral
geometry around the tin atom. – Thermolysis of 5 at 100 °C
2
synthesis of hetero-polysilanes (poly-carbosilanes, poly- led to the deposition of thin films of tin; photolysis resulted
germasilanes, poly-stannasilanes). The silylene 1 was found in the formation of tin powder. All thermolysis products could
to be inert towards all substrates except SnCl and PbCl be isolated and were characterized as SnCl , elemental tin,
Reaction with SnCl led to the formation of the yellow, LЈSi: (1), LЈSiCl (6) and the new disilane LЈSi(Cl)-(Cl)SiLЈ (7).
tris(silyl)stannane [(LЈSiCl) SnCl] (5) and elemental tin. The Photolysis led to a reduced product spectrum (formation of
photolabile (5) was characterized by multinuclear NMR ( H, Sn + SnCl + 7). Reaction of 1 with PbCl gave elemental
lead and LЈSiCl as the only products.
2
2
.
2
2
2
3
1
2
2
1
3
29
119
C,
Si,
Sn) and single crystal X-ray diffraction:
2
30 4 6 3
C H60Cl N Si Sn, M = 849.60, orthorhombic, space group
The heavy analogs of carbenes R E: (E ϭ Si, Ge, Sn, Pb) Scheme 1
2
are attractive building blocks for the synthesis of inorganic
polymers [R E] . Homo-polymers of silicon, germanium,
2
n
and tin are typically obtained by the reduction of the dihal-
[
1]
[2]
[3]
ides R SiCl , R GeCl , or R SnCl
These reactions
2
2
2
2
2
2.
may proceed through the intermediacy of free silylenes, ger-
mylenes or stannylenes as reactive intermediates. The un-
[
1]
[2]
ique electronic structure of poly-silanes , poly-germanes ,
[
3]
and poly-stannanes has prompted detailed investigations
of their physical properties. The partial replacement of sili-
con in poly-silanes by germanium or tin is of special interest
as a 1-dimensional model for SiϪGe and SiϪSn alloys. The
dehalogenation of mixtures of dichlorides R ECl has been
2
2
[4]
used to obtain copolymers of type [R Si] [RЈ Si]
R Si] [R Ge] , but the very different susceptibility of the
and
2
n
2
k
and Pb) was investigated by Gehrhus, Hitchcock, and Lap-
pert and was shown to proceed by insertion of the silylene
[
4]
[
2
n
2
k
SiCl, GeCl, and SnCl bonds towards reduction limits the
scope of the dehalogenation approach.
4
into the MN bond rather than formation of Si,Ge-, Si,Sn-
[8a][8b]
or Si,Pb copolymers.
Similar MN insertion products
[5][6]
The recent synthesis of a number of stable carbenes
were obtained by Weidenbruch et al. from the reaction of a
[
7][8]
and silylenes
presents a new possible strategy to obtain
[8c]
stable diaminogermylene with a stable diaminosilylene.
group 14 polymers by copolymerization of these reactive
molecules. We now report preliminary results on the reac-
tion of the stable silylene LЈSi (1)[ with the stable divalent
No reaction was observed between the silylene 1 (LЈSi:)
and CO, LЈC: or LЈGe: or any other combination of these
compounds even after prolonged heating to 150°C in sealed
NMR tubes. Rapid reaction occurred between 1 and tin(II)
7]
[9]
group 14 compounds: CO, SnCl , PbCl , LЈC: (2) and
2
2
[
10]
LЈGe: (3)
The reaction of the stable silylene 4 with the germylenes,
stannylenes, and plumbylenes M[N(SiMe) ] (M ϭ Ge, Sn
(Scheme 1).
[11]
chloride, however, to give the tris(silyl)stannane 5.
Compound 5 was characterized by multinuclear NMR
(1H, C, Si, and
13
29
119
[11]
[11]
3
2
Sn) , CI-MS
and single crystal
as a tris(silyl)stannane with SnIV
and Si centers. The oxidation of both divalent silicon and
[
12][19]
X-ray diffraction
[
᭛]
Part 6: Ref.[6]
IV
.
Eur. J. Inorg. Chem. 1998, 1067Ϫ1070

WILEY-VCH Verlag GmbH, D-69451 Weinheim, 1998
1434Ϫ1948/98/0808Ϫ1067 $ 17.50ϩ.50/0
1067

M. K. Denk, K. Hatano, A. J. Lough
FULL PAPER
Figure 1. Molecular structure of 5 (ORTEP plot, 50% probability
[
a]
level, hydrogen atoms have been omitted for clarity)
tin in the course of the reaction is balanced by the forma-
tion of a stoichiometric amount of metallic tin. Compound
5
can be stored at Ϫ10°C in the dark for months, but slowly
decompose to give deposits of metallic tin at r. t. especially
if exposed to light.
[13]
The decomposition of 5 under thermolytic
or photo-
[
14]
lytic
conditions follows different pathways. Both reac-
tions lead to a fragmentation of the Si Sn framework and
3
[a]
Selected bond lengths [pm] and angles [°]: Sn(1)ϪCl(4) 238.8(3),
Sn(1)ϪSi(1) 263.0(4), Sn(1)ϪSi(2) 264.2(4), Sn(1)ϪSi(3) 264.0(3),
the formation of the disilane 7.[ Elemental tin is de-
15]
posited as film (thermolysis) or powder (photolysis). Under Cl(1)ϪSi(1) 211.2(5), Cl(2)ϪSi(2) 209.3(5), Cl(3)ϪSi(3) 211.6(4);
thermolytic conditions, the silylene 1,[ and the silane 6
7a]
[7a]
Cl(4)ϪSn(1)ϪSi(1) 102.96(11), Cl(4)ϪSn(1)ϪSi(2) 102.57(13),
Cl(4)ϪSn(1)ϪSi(3) 100.07(12), Si(1)ϪSn(1)ϪSi(2) 116.38(11),
are formed as additional products. The thermolytic de- Si(1)ϪSn(1)ϪSi(3) 116.7(2), Si(2)ϪSn(1)ϪSi(3) 114.60(12); Torsio-
nal angles: Cl(4)ϪSn(1)ϪSi(1)ϪCl(1) Ϫ50.15(0.18), Cl(4)ϪSn(1)Ϫ
Si(3)ϪCl(3) Ϫ50.50(0.23), Cl(4)ϪSn(1)ϪSi(2)ϪCl(2) Ϫ47.95(0.17)
composition pathway of 5 matches the CI-MS fragmen-
[
11]
ϩ•
tation pattern (high abundance of the fragments [LЈSi:]
ϩ•
and [LЈSiCl ] ).
2
The crystal structure of 5[12][19] (Figure 1) shows the tin
atom in a distorted tetrahedral environment. The SiϪSnϪSi
bond angles (114.60Ϫ116.70°) and SiϪSnϪCl bond angles
match those reported for the recently characterized silyl-
stannanes [(Me Si) Si] SnCl (259.7Ϫ260.4 pm)
(100.07Ϫ102.96°) deviate from the ideal tetrahedral ge-
[16]
and
3
3
2
2
ometry. Few structural data are available on silyl-stannanes,
but the Si-Sn bond distances in 5 (263.0Ϫ264.2 pm) closely
[17]
[
(Me Si) Sn] (260.9Ϫ261.1 pm).
3 3 2
The normal SiϪSn bond distances, and especially the fact
that the SiϪSn bonds of 5 are freely rotating in solution
1
(
equivalence of 6 tBu groups and 6 ring protons in the H
NMR at r.t.), show that 5 is free of strong steric congestion.
By contrast, the disilane LЈSi(Cl)Ϫ(Cl)SiLЈ (7, vide infra)
shows hindered rotation of the tBu-groups at r.t, as evi-
denced by the broad signals found for the methyl groups in
1
13
the H- and C-spectrum. The (SiCl) SnϪCl framework
3
has the idealized symmetry C , with ClϪSnϪSiϪCl tor-
3
sional angles ranging from Ϫ47.95 to Ϫ50.15.
The reaction of 1 with PbCl leads to the clean formation
2
of elemental lead (powder) and LЈSiCl2 (6) as the only
products.
Stable silylenes of type 1 can at present only be obtained
by reduction of the corresponding dihalosilanes R SiCl
2
2
with potassium at elevated temperatures[ . The thermo-
lytic generation of 1 from a stannylsilane such as 5 presents
a potential alternative synthetic approach. The stannyl-
silanes LЈSi(SnR )(Cl) and LЈSi(SnR ) are now under
7a]
3
3 2
investigation as new precursors for stable silylenes.
The authors thank the Natural Sciences and Engineering Re-
search Council of Canada (NSERC) and the Connaught Fund of
the University of Toronto for support of this research, Dr. Juris
Strautmanis (Toronto) for many helpful discussions and Avinash
Thadani for preliminary experiments.
1068
Eur. J. Inorg. Chem. 1998, 1067Ϫ1070

Synthesis and Reactivity of Low-Coordinate Compounds, 7
FULL PAPER
[
5i]
J. Marshall, J. Am. Chem. Soc. 1996, 118, 11027Ϫ11028. Ϫ
Experimental Section
General: All reactions were carried out under argon (99.994%
T. A. Taton, P. Chen, Angew. Chem. 1996, 108, 1098Ϫ1100;
Angew. Chem. Int. Ed. Engl. 1996, 35, 1011Ϫ1013.
6]
[
M. K. Denk, A. Thadani, K. Hatano, A. J. Lough, Angew.
Chem. Int. Ed. Engl. 1997, 36, 2607Ϫ2609; Angew. Chem. 1997,
purity) with usual Schlenk equipment or inside an inert-gas glove-
box (O
over benzophenone/potassium (THF, hexanes, benzene) or by 30
minute sonication with CaH . Ϫ IR: Nicolet. Ϫ NMR: Varian
Gemini 200, Unity 400 and 500. Ϫ The starting materials LЈSi
2 2
and H O < 1 ppm). Solvents were purified by distillation
1
09, 2719Ϫ2721.
[7] [7a]
M. Denk, R. Lennon, R. Hayashi, R. West, R. V. Belyakov,
2
H. P. Verne, A. Haaland, M. Wagner, N. Metzler, J. Am. Chem.
[
7b]
Soc. 1994, 116, 2691Ϫ2692. Ϫ
West, J. Chem. Soc., Chem. Commun. 1994, 33Ϫ34. Ϫ
Denk, J. Green, N. Metzler, M. Wagner, J. Chem. Soc., Dalton
M. Denk, R. Hayashi, R.
[7c]
[
7a]
[9]
[10]
M.
N. Metzler, M. Denk, J. Chem.
(
1)
lished procedures. The compounds 1؊3 were purified by subli-
mation under exclusion of air and moisture. Anhydrous SnCl was
used as received (Aldrich). Reactions of 1 with CO, LЈC: and LЈGe:
were studied in ca. 5 wt.-% solutions in C . Flame sealed
samples were heated to 150°C for 4 weeks in 5-mm NMR tubes.
LЈC: (2) and LЈGe: (3)
were obtained according to pub-
[7d]
Trans. 1994, 2405Ϫ2410. Ϫ
Soc., Chem. Commun. 1996, 2657Ϫ2658.
8] [8a]
2
[
B. Gehrhus, P. B. Hitchcock, M. F. Lappert, Angew. Chem.
Int. Ed. Engl. 1997, 36, 2514Ϫ2516; Angew. Chem. 1997, 109,
6 6
D
[8b]
2
624Ϫ2626. Ϫ
C. Drost, B. Gehrhus, P. B. Hitchcock, M.
F. Lappert, J. Chem. Soc., Chem. Commun. 1997, 1845Ϫ1846.
For the synthesis and characterization of 6 see reference[
7a]
.
[8c]
Ϫ
A. Schäfer, W. Saak, M. Weidenbruch, H. Marsmann, G.
Henkel, Chem. Ber. 1997, 130, 1733 Ϫ 1737.
Synthesis of 5: SnCl (10.0 mmol, 1.896 g) is added to a solution
2
[9]
Obtained from the imidazolium salt by deprotonation as de-
scribed in: A. J. Arduengo, J. Am. Chem. Soc. 1992, 114,
5530Ϫ5534.
of the silylene 1 (20.0 mmol, 3.927 g) in 15 ml of THF at Ϫ10°C.
The reaction mixture turns red and the starting material is com-
pletely consumed after 60 min. The crude reaction mixture contains
[10]
W. A. Herrmann, M. Denk, J. Behm, W. Scherer, F.-R. Klingan,
H. Bock, B. Solouki, M. Wagner, Angew. Chem. 1992, 104,
5
(> 85%) and small amounts (ca. 5%) of 6 and 7. Analytically
1
(
489Ϫ1492; Angew. Chem. Int. Ed. Engl. 1992, 31, 1485Ϫ1488.
pure (LЈSiCl) SnCl (5) is isolated from the crude reaction mixture
3
[11]
1
LЈSiCl) SnCl (5): H NMR (200 MHz, C D ): δ 1.45 (s, 54 H,
3
6
6
4 1
by chromatography on Celite (hexane as eluent), followed by
recrystallization from toluene as orange crystals (46%) that decom-
pose at 172°C without melting.
CH ), 5.83 [s, 6 H, ϭCH, tin satellites corresponding to J( H,
3
1
17/119
1
13
Sn) ϭ 7.8 Hz]. Ϫ C NMR (100 MHz, C ): δ 31.43
6
D
6
[q, J(C,H) ϭ 121.5 Hz, CH
3
], 53.13 [s, C(CH ) ], 115.33 [dd,
3 3
1
2
29
J(C,H) ϭ 181.6 Hz, J(C,H) ϭ 8.8 Hz, ϭCH]. Ϫ Si NMR
1
29 117
(
6 6
79.0 MHz, C D ): δ Ϫ20.08 [ J( Si, Sn) ϭ 881 Hz,
29 119 119
1
J( Si, Sn) ϭ 923 Hz]. Ϫ
Sn NMR (186.0 MHz, C
6
D
6
):
1
29 119
Ƞ)
Ϫ222.6 ppm [ J( Si, Sn) ϭ 922 Hz]. Ϫ CI-MS (ϩ, iso-
Dedicated to Professor Heinrich Nöth on the occasion of his
ϩ
ϩ•.
butane) m/z (rel. int.): 849 [M ϩ 1] (1), 582 [M Ϫ LЈSi:] (2),
70th birthday.
ϩ•
ϩ•
[
1] [1a]
462 (11), 266 [LЈSiCl
]
(90), 196 [LЈSi] (100). Ϫ IR (nujol):
ν ϭ cm : 3107 w, 1639 m, 1598 m, 1393 m, 1368 s, 1343 m,
270 s, 1212 s, 1196 s, 1122 s, 1106 s, 1089 s, 1048 s, 999 s, 810
m, 744 s, 663 s, 647 s.
D. Miller, J. Michl, Chem. Rev. 1989, 89, 1359Ϫ1410. Ϫ
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˜
2
Ϫ1
[
1b]
1
Chapter 3, 77Ϫ110, (Eds.: E. W. Abel, F. G. A. Stone, G. Wilk-
inson), Pergamon Press, New York, 1995 and references therein.
Ϫ
[12]
[19]
[
1c]
X-ray Crystallographic Study : C30
H
60Cl
1
N
Si
3
˚
Sn, 5, M ϭ
H. Sakurai, Synthesis and Applications of Polysilanes,
4
6
8
49.60, orthorhombic, space group Pca2
, a ϭ 11.365(3) A, b ϭ
CMC, Tokyo, 1989.
˚
˚
˚
3
[
2] [2a]
18.999(4) A, c ϭ 19.808(5) A, V ϭ 4277(2) A , Z ϭ 4,
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P. Trefonas, R. West, J. Polym. Sci., Polym. Chem. Ed. 1985,
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3, 2099Ϫ2017. Ϫ
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W. J.
K. Mochida, T. Ohkawa, H. Kawata,
˚
α
tor, λ (Mo-K ) ϭ 0.71073 A. The intensities of standard reflec-
[2d]
tions measured every 97 reflections showed no decay. The data
were corrected for Lorentz and polarization effects and semi-
empirical absorption correction was applied using ψ-scans.
Minimum and maximum absorption corrections were 0.5712
and 0.5276. The structure were solved and refined using the
package. Refinement was by full-matrix le-
ast-squares on F using all data (negative intensities included).
1
993, 26, 869Ϫ871. Ϫ
A. Watanabe, O. Ito, M. Matsuda, Bull. Chem. Soc. Jpn. 1996,
[2e]
6
9, 2993Ϫ2998. Ϫ
K. Mochida, S. Nagano, S. Maeyama, T.
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[
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[
3b]
K. Mochida, M. Hayakawa, T. Tsuchikawa, Y. Yokoyama,
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2
2
o
The weighting scheme was w ϭ 1/[σ (F ) ϩ (0.00295P) ϩ
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2
4] [4a]
o c
4.7P] where P ϭ (F ϩ F )/3. Hydrogen atoms were included
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[
4b]
in fixed positions and treated as riding atoms. Maximum re-
˚
ecules 1989, 22, 1697Ϫ1704. Ϫ
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3
[4c]
sidual electron densities were ϩ0.875 and Ϫ0.557 e/A .
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T. Shono, S. Kashimura, H. Murase, J. Chem. Soc., Chem.
[13]
1
13
6 6
Sealed NMR samples of 5 in C D were monitored by H, C,
[
4d]
29
Ϫ
and Si NMR. After 3 h at 100°C, the decomposition was
complete and LЈSi: (1), LЈSiCl (6) and LЈSi(Cl)Ϫ(Cl)SiLЈ (7)
[
4e]
Commun. 1992, 896Ϫ897. Ϫ
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A. Watanabe, H. Miike, Y. Tsu-
2
[
4f]
1
were formed in the molar ratio 2:6:3 ( H NMR). The NMR
tubes were stored “upside down” during the thermolysis to pre-
vent the formation of a tin film in the bottom part of the
NMR tube.
14]
[
4g]
Phys. Lett. 1994, 65, 1358Ϫ1360. Ϫ
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[4h]
A. Watanabe, T.
K. Huang, L. A. Ver-
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Irradiation of 5 (5% in hexanes) in a quartz tube for 6 days
[
4i]
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2
and tin powder as sole products.
[
5] [5a]
[15]
A. J. Arduengo, R. L. Harlow, M. Kline, J. Am. Chem. Soc.
The disilane 7 has been obtained earlier in our group from reac-
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[5b]
1
991, 113, 361Ϫ363. Ϫ
M. Regitz, Angew. Chem. 1991, 103,
1
6
91Ϫ693; Angew. Chem. Int. Ed. Engl. 1991, 30, 674Ϫ676. Ϫ
(7): H NMR (200 MHz, C
6
D
6
): δ 1.25Ϫ1.50 (br, 36 H, CH
3
),
): δ
3 3
) ], 114.08 (ϭCH). Ϫ
[
5c]
13
A. J. Arduengo, H. V. Rasika-Dias, R. L. Harlow, M. Kline,
5.8 (s, 4 H, ϭCH). Ϫ C NMR (100 MHz, C
6 6
D
[5d]
J. Am. Chem. Soc. 1992, 114, 5530Ϫ5534. Ϫ
A. J. Arduengo,
30.25Ϫ31.50 (br, CH ), 52.88 [s, C(CH
3
2
9
H. V. Rasika-Dias, D. A. Dixon, R. L. Harlow, W. T. Klooster,
6 6
Si NMR (79.0 MHz, C D ): δ Ϫ33.18. EI-MS (40 eV) m/z
[5e]
T. F. Koetzle, J. Am. Chem. Soc. 1994, 116, 6812Ϫ6822. Ϫ
(rel. int.): 466 (4), 465 (5), 464 (14), 463 (7), 462 (20), 295 (6),
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Chem. 1996, 108, 2980Ϫ2982; Angew. Chem. Int. Ed. Engl.
294 (3), 293 (9), 270 (7), 269 (6), 268 (39), 267 (10), 266 (55)
ϩ•
LЈSiCl ϭ [M Ϫ LЈSi:] , 253 (2), 251 (3), 239 (11), 238 (7), 237
2
[5f]
ϩ
1
996, 35, 2805Ϫ2807. Ϫ
M. Regitz, Angew. Chem. 1996, 108,
(15), 236 (5), 233 (8), 232 (4), 231 (22) [LЈSi-Cl] , 222 (3), 214
7
91Ϫ794; Angew. Chem. Int. Ed. Engl. 1996, 35, 725Ϫ728. Ϫ
(7), 213 (6), 212 (36), 211 (12), 210 (51), 209 (7), 198 (6), 197
[
5g]
ϩ•
R. W. Alder, P. R. Allen, M. Murray, A. G. Orpen, Angew.
(20), 196 (100) [LЈSi] , 195 (5), 158 (9), 156 (7), 156 (41), 155
Chem. 1996, 108, 1211Ϫ1213; Angew. Chem. Int. Ed. Engl.
(12), 154 (62), 153 (7), 140 (21), 133 (3), 125 (16), 121 (32), 120
(12), 119 (87), 99 (5), 94 (4), 92 (10), 85 (14), 84 (53), 83 (3), 57
1
996, 35, 1121Ϫ1122. Ϫ [ A. J. Arduengo, J. R. Goerlich, W.
5h]
Eur. J. Inorg. Chem. 1998, 1067Ϫ1070
1069

M. K. Denk, K. Hatano, A. J. Lough
FULL PAPER
[19]
(
8). The identity of the compound has also been confirmed by
Crystallographic data (excluding structure factors) for the struc-
ture of 5 have been deposited with the Cambridge Crystallo-
graphic Data Centre as supplementary publication no. CCDC-
101272. Copies of the data can be obtained free of charge on
applications to the Director, CCDC, 12 Union Road, Cam-
bridge CB2 1EZ, UK (fax: Int. Code ϩ44(0)1223/ 336-033. E-
mail: deposit@chemcrys.cam.ac.uk).
single crystal X-ray diffraction (M. Denk, unpublished results).
[
[
[
16]
17]
18]
S. P. Mallela, R. A. Geanangel, Inorg. Chem., 1990, 29,
3
525Ϫ3528.
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