A bis(silyl)nickel complex containing an o-carboranylene and its application in facile double silylation of alkynes and alkenes

Article abstract of DOI:10.1021/om990915q

The reaction of 1,2-bis(dimethylsilyl)carborane (1) with Ni(PEt₃)₄ yielded the cyclic bis-(silyl)nickel complex (2). 2 was found to be a good catalyst for the double silylation reaction of alkynes and alkenes. Thus, the reaction of 1 with RC≡CR′ in the presence of a catalytic amount of 2 afforded the six-membered disilylene ring compounds o-B₁₀H₁₀C₂(SiMe₂)₂(RC= CR′) (R = R′ = Ph (3); R = Ph, R′ = H (4); R = R′ = Et (5); R = Ph, R′ = Me (6); R = R′ = Me (7)). In contrast, the reaction of 1-phenyl-2-(trimethylsilyl)acetylene with 1 in the presence of a catalytic amount of 2 afforded the six-membered disilylene ring compound (9) and the five-membered disilylene ring compound (10). The stoichiometric reaction of 2 with an active alkyne such as dimethyl acetylenedicarboxylate gave the six-membered disilylene ring compound (11). The intermedate 2 also was found to be a good catalyst for the double silylation of some alkenes. Thus, the reaction of 1 with 4-vinylanisole in the presence of a catalytic amount of 2 afforded the five-membered disilylene ring compound (15). However, treatment of 1 with 1,1-diphenylethylene under the same reaction conditions yielded a different type of five-membered disilylene ring compound (17). The reaction of 1 with 2,3-dimethylbutadiene in the presence of the nickel catalyst also was studied. The crystal structures of 2, 9, and 14 are described.

Full text of DOI:10.1021/om990915q

1722
Organometallics 2000, 19, 1722-1728
A Bis(silyl)n ick el Com p lex Con ta in in g a n
o-Ca r bor a n ylen e a n d Its Ap p lica tion in F a cile Dou ble
Silyla tion of Alk yn es a n d Alk en es
Youngjin Kang,† J unghyun Lee,‡ Young Kun Kong,‡ Sang Ook Kang,*,† and
J aejung Ko*,†
Department of Chemistry, Korea University, Chochiwon, Chungnam 339-700, Korea, and
Department of Chemistry, Kyonggi University, Suwon, Kyunggido 440-760, Korea
Received November 22, 1999
The reaction of 1,2-bis(dimethylsilyl)carborane (1) with Ni(PEt3)4 yielded the cyclic bis-
(silyl)nickel complex (2). 2 was found to be a good catalyst for the double silylation reaction
of alkynes and alkenes. Thus, the reaction of 1 with RCtCR′ in the presence of a catalytic
amount of 2 afforded the six-membered disilylene ring compounds o-B10H10C2(SiMe2)2(RCd
CR′) (R ) R′ ) Ph (3); R ) Ph, R′ ) H (4); R ) R′ ) Et (5); R ) Ph, R′ ) Me (6); R ) R′ )
Me (7)). In contrast, the reaction of 1-phenyl-2-(trimethylsilyl)acetylene with 1 in the presence
of a catalytic amount of 2 afforded the six-membered disilylene ring compound (9) and the
five-membered disilylene ring compound (10). The stoichiometric reaction of 2 with an active
alkyne such as dimethyl acetylenedicarboxylate gave the six-membered disilylene ring
compound (11). The intermedate 2 also was found to be a good catalyst for the double
silylation of some alkenes. Thus, the reaction of 1 with 4-vinylanisole in the presence of a
catalytic amount of 2 afforded the five-membered disilylene ring compound (15). However,
treatment of 1 with 1,1-diphenylethylene under the same reaction conditions yielded a
different type of five-membered disilylene ring compound (17). The reaction of 1 with 2,3-
dimethylbutadiene in the presence of the nickel catalyst also was studied. The crystal
structures of 2, 9, and 14 are described.
In tr od u ction
resulting from strongly electron-withdrawing silyl groups
(e.g., SiF3 or SiCl3)8 or from the inclusion of the silyl
groups in a chelate ring.9 Isolation and fundamental
knowledge of the reactivity of bis(silyl)nickel complexes
are essential to understand their role as catalytic
intermediates.
Recently, we reported the double silylation reactions
of a cyclic bis(silyl)platinum complex containing an
o-carboranylene.10 However, the double silylation reac-
tions were stoichiometric processes involving reaction
of a stable PtSi2P2 complex with a variety of unsatur-
ated organic substrates. A catalytic process would be
preferred. Accordingly, we have started a study of the
synthesis of bis(silyl)metal complexes that would be
suitable as catalysts.
The double silylation of unsaturated organic sub-
strates catalyzed by group 10 metal complexes1 has been
well documented for two decades. Nickel complexes, in
particular, provide excellent catalysts for such reactions
of silicon-containing linear compounds2 and 1,2-disila-
cyclobutene.3 Bis(silyl)nickel complexes have been im-
plicated as intermediates in the nickel-catalyzed double
silylation of arenes,4 alkynes,5 alkenes,6 and aldehydes.7
In contrast to analogous platinum complexes, bis(silyl)-
nickel complexes in general have not been isolated due
to their instability. The few bis(silyl)nickel complexes
that have been isolated possess special stabilization
† Korea University.
Here we report the general synthesis of a new class
of stable cyclic bis(silyl)nickel complex with a bulky
‡ Kyonggi University.
(1) (a) Beletskaya, I.; Moberg, C. Chem. Rev. 1999, 99, 3435. (b)
Sharma, H. K.; Pannell, K. H. Chem. Rev. 1995, 95, 1351. (c)
Braunstein, P.; Knorr, M. J . Organomet. Chem. 1995, 500, 21. (d)
Okinoshima, H.; Yamamoto, K.; Kumada, M. J . Organomet. Chem.
1975, 86, C27. (e) Sakurai, H.; Kamiyama, Y.; Nakadaira, Y. J . Am.
Chem. Soc. 1975, 97, 931. (f) Carson, C. W.; West, R. Organometallics
1983, 2, 1081. (g) Seyferth, D.; Goldman, E. W.; Escudie´, J . J .
Organomet. Chem. 1984, 271, 337. (h) Yamashita, H.; Catellani, M.;
Tanaka, M. Chem. Lett. 1991, 241. (i) Murakami, M.; Andersson, P.
G.; Suginome, M.; Ito, Y. J . Am. Chem. Soc. 1991, 113, 3987. (j) Finckh,
W.; Tang, B.; Lough, A.; Manners, I. Organometallics 1992, 11, 2904.
(2) (a) Tamao, K.; Miyake, N.; Kiso, Y.; Kumada, M. J . Am. Chem.
Soc. 1975, 97, 5603. (b) Okinoshima, H.; Yamamoto, K.; Kumada, M.
J . Am. Chem. Soc. 1972, 94, 9263. (c) Ishikawa, M.; Nishimura, Y.;
Sakamoto, N.; Ono, T.; Ohshita, J . Organometallics 1992, 11, 483.
(3) J zang, T.; Lee, C.; Liu, C. S. Organometallics 1988, 7, 1265.
(4) (a) Ishikawa, M.; Sakamoto, H.; Okazaki, S.; Naka, A. J .
Organomet. Chem. 1992, 439, 19. (b) Ishikawa, M.; Okazaki, S.; Naka,
A.; Sakamoto, H. Organometallics 1992, 11, 4135.
(5) (a) Naka, A.; Okazaki, S.; Hayashi, M.; Ishikawa, M. J . Orga-
nomet. Chem. 1995, 499, 35. (b) Ishikawa, M.; Ohshita, J .; Ito, Y.
Organometallics 1986, 5, 1518. (c) Kiso, Y.; Tamao, K.; Kumada, M.
J . Organomet. Chem. 1974, 76, 105. (d) Ishikawa, M.; Matsuzawa, S.;
Hirotsu, K.; Kamitori, S.; Higuchi, T. Organometallics 1984, 3, 1930.
(e) Ishikawa, M.; Matsuzawa, S.; Higuchi, T.; Kamitori, S.; Hirotsu,
K. Organometallics 1985, 4, 2040.
(6) Ishikawa, M.; Okazaki, S.; Naka, A.; Tachibana, A.; Kawauchi,
S.; Yamabe, T. Organometallics 1995, 14, 114.
(7) Ishikawa, M.; Naka, A.; Okazaki, S.; Sakamoto, H. Organome-
tallics 1993, 12, 87.
(8) (a) Bierschenk, T. R.; Guerra, M. A.; J uhlke, T. J .; Larson, S.
B.; Lagow, R. J . J . Am. Chem. Soc. 1987, 109, 4855. (b) Kiso, Y.; Tamao,
K.; Kumada, M. J . Organomet. Chem. 1974, 76, 95.
(9) Ohshita, J .; Isomura, Y.; Ishikawa, M. Organometallics 1989,
8, 2050.
(10) Kang, Y.; Kang, S. O.; Ko. J . Organometallics 1999, 18, 1818.
10.1021/om990915q CCC: $19.00 © 2000 American Chemical Society
Publication on Web 03/30/2000

Bis(silyl)nickel Complex
Organometallics, Vol. 19, No. 9, 2000 1723
o-carboranylene and a variety of their double silylation
reactions with unsaturated organic compounds. A por-
tion of this study has already been communicated.11
Resu lts a n d Discu ssion
Syn th esis of [o-(SiMe2)2C2B10H10]Ni(P Et3)2 Com -
p lex 2. In our search for a stable bis(silyl)nickel
complex, we investigated the reaction of o-bis(dimeth-
ylsilyl)carborane with Ni(PEt3)4. When 1.2 equiv of
o-bis(dimethylsilyl) carborane 1 was treated with 1
equiv of Ni(PEt3)4 in pentane at 25 °C, an immediate
color change from yellow to deep red occurred with
evolution of H2 (eq 1). Standard workup and crystal-
F igu r e 1. X-ray crystal structure of 2 with 50% probability
thermal ellipsoids depicted. Selected bond lengths (Å) and
angles (deg): Ni(1)-P(1) 2.2265(8), Ni(1)-P(2) 2.2346(8),
Ni(1)-Si(1) 2.2371(9), Ni(1)-Si(2) 2.2477(9), Si(1)-C(1B)
1.1941(3), Si(2)-C(2B) 1.940(3), C(1B)-C(2B) 1.669(4),
P(1)-Ni(1)-P(2) 101.95(3), Si(1)-Ni(1)-Si(2) 83.69(3), P(1)-
Ni(1)-Si(1) 96.06(3), P(2)-Ni(1)-Si(1) 140.35(4).
lization from toluene-pentane gave [o-(SiMe2)2 C2B10H10]-
Ni(PEt3)2 (2) in 86% yield as a dark red, crystalline solid
which is quite sensitive to air, but stable during brief
heating to 100-110 °C. The unusual thermal stability
of 2 may be related to the advantageous properties of
the carboranylene, including electronic and steric ef-
fects. Compound 2 is soluble in toluene, THF, and
(PEt3)4 catalyst or by reacting 1 and the alkyne in the
presence of a catalytic quantity of the nickel intermedi-
ate 2. Because the former procedure may in some cases
result in formation of the cyclotrimerization product, the
latter procedure is preferred. Thus, the reaction of 1
(0.12 g, 0.46 mmol) with diphenylacetylene (0.09 g, 0.51
mmol) in the presence of a catalytic amount of 2 (0.01
g, 0.018 mmol) was stirred under the conditions speci-
fied in Table 1. Subsequent recrystallization gave 5,6-
carboranylene-1,1,4,4-tetramethyl-2,3-diphenyl-1,4-dis-
ilacyclohex-2-ene (3) by insertion of the carbon-carbon
triple bond into a silicon-nickel bond of 2 (entry 1).
In a similar fashion, the nickel-catalyzed reaction of
1 with other alkynes such as phenylacetylene, 3-hexyne,
and 2-butyne at 80 °C also yielded the six-membered-
ring compounds. However, the reaction course was quite
sensitive to the reaction conditions. When the reaction
of o-bis(dimethylsilyl)carborane 1 with 1-phenyl-1-pro-
pyne (1 equiv) in the presence of a catalytic amount of
2 (0.03 equiv) was carried out at 70-80 °C, the major
product was identified as 1,3,5-trimethyl-2,4,6-triph-
enylbenzene, which was characterized by spectroscopic
techniques. However, the same reaction when carried
out at room temperature gave the six-membred-ring
compound 6 in high yield (entry 4). The spectral data
for 3-5 and 7 were identical with those of the authentic
samples.15
1
chloroform and was characterized by H, 13C, 31P, and
29Si NMR, mass spectroscopy, and elemental analysis.
The initial indication of the formulation for 2 stemmed
from the observation of a parent ion in the mass
spectrum at m/z 553. The 31P NMR signal was shifted
12
from -2.2 ppm for Ni(PEt3)3 to 5.58 ppm. The struc-
ture of 2 was unambiguously established by single-
crystal X-ray analysis and is shown in Figure 1.
Crystallographic data and processing parameters are
given in Table 3. Complex 2 has a distorted tetrahedral
geometry with the dihedral angle between P(1)-Ni(1)-
P(2) and Si(1)-Ni(1)-Si(2) being 86.03°. The average
Ni-Si bond length [2.2424(9) Å] is slightly longer than
13
the 2.171(3) Å in [(µ-Cl)2Ni2(SiCl3)4][(CMe3)2C5H3NH]2
or 2.182(4) Å in (SiF3)2Ni(PMe3)3,8a but shorter than that
of the calculated Ni-Si bond length of 2.525 Å for
1-nickela-2,5-disilacyclopent-3-ene.6 The relatively long
Ni-Si bonds of 2 may indicate that they are relatively
weak. The Ni-P bond distance [2.2305(8) Å] is compa-
rable to those in Ni(PPh3)2(C2H4) (2.15 Å) and Ni(PCy3)2-
(η-CO2) (2.15 Å).14
Nick el-Ca ta lyzed Rea ction w ith Alk yn es. Al-
though the cyclic bis(silyl)platinum complex Me2Si-
(o-C2B10H10)SiMe2Pt(PPh3)2 is not a catalyst for the
double silylation reaction due to its strong Pt-Si bond
strength, the Ni complex 2 was found to be a good
catalyst for the double silylation reaction. The nickel-
catalyzed double silylation can be carried out either by
reacting 1 and the alkyne in the presence of the Ni-
When 1-hexyne was employed as a terminal alkyne
in the nickel-catalyzed reaction of 1 at 80 °C, the five-
membered-ring compound 8 was isolated as a colorless
liquid in 71% yield (entry 6). The isolation of 8 is
interesting because a 1,2-hydrogen shift must be in-
volved in its formation. Such a 1,2-hydrogen shift has
been observed in the stoichiometric reaction of Me2Si-
(o-C2B10H10)SiMe2Pt(PPh3)2 with 1-hexyne.10 Similar
reaction of 1 with 1-phenyl-2-(trimethylsilyl)acetylene
at room temperature afforded 5,6-carboranylene-1,1,
(11) Kang, Y.; Lee, J .; Kong, Y. K.; Kang, S. O.; Ko, J . Chem.
Commun. 1998, 2343.
(12) Tolman, C. A.; Gerlach, D. H.; J esson, J . P.; Schunn, R. A. J .
Organomet. Chem. 1974, 65, C23.
(13) Brezinski, M. M.; Schneider, J .; Radonovich, L. J .; Klabunde,
K. J . Inorg. Chem. 1989, 28, 2414.
(14) Aresta, M.; Nobile, C. F.; Albano, V. G.; Forni, E.; Manassero,
M. J . Chem. Soc., Chem. Commun. 1975, 636.
(15) Kang, Y.; Kang, S. O.; Ko, J . Organometallics, in press.

1724 Organometallics, Vol. 19, No. 9, 2000
Kang et al.
Ta ble 1. Nick el-Ca ta lyzed Rea ction s of Alk yn es
w ith 1,2-Bis(d im eth ylsilyl)ca r bor a n e
Ta ble 2. Nick el-Ca ta lyzed Rea ction s of Alk en es
w ith 1,2-Bis(d im eth ylsilyl)ca r bor a n e
a
Stoichiometric reaction.
Ta ble 3. Cr ysta l Da ta of 2, 9, a n d 14
2
9
14
empirical formula
molecular wt
cryst syst
space group
a (Å)
C18H52B10NiP2PtSi2 C17H36B10Si3 C14H28B10Si2
553.53
432.83.
360.64
monoclinic
P2(1)/n
9.4833(6)
19.2061(13)
16.8724(10)
90
monoclinic
P21/n
10.1510(8)
21.3249(10) 18.2763(15)
12.4886(5)
monoclinic
P21/n
9.6874(4)
b (Å)
c (Å)
12.7310(7)
R (deg)
â (deg)
93.029(2)
90
96.944(5)
106.587(4)
γ (deg)
V, Å3
3068.8(3)
4
2683.6(3)
4
2160.2(2)
4
Z value
D(calcd),
1.198
1.071
1.109
(g cm-3
)
F(000)
1184
0.823
920
0.181
760
0.160
abs coeff, mm-1
λ, (Å)
a
Stoichiometric reaction.
0.71073
graphite
ω-2θ
4.80-58.40
14984
0.71073
graphite
ω-2θ
3.80-51.94
5513
0.71073
graphite
ω-2θ
4.02-51.94
4494
monochromator
scan type
2θ range, deg
no. of reflns
measd
4,4-tetramethyl-2-phenyl-3-trimethysilyl-1,4-disila-
cyclohex-2-ene (9) and 4,5-carboranylene-1,1,3,3-tetra-
methyl-2-[phenyl(trimethylsilyl)methylene]-1,3-disilacy-
clopentane (10) in 62% and 8% yield, respectively. The
products 9 and 10 could readily be isolated by prepara-
tive GLC. The 1H NMR spectrum of 9 contains three
resonances at 0.50, 0.13, and -0.21 ppm, assigned to
three kinds of methyl groups. In the olefinic region of
the 13C NMR spectrum of 9, two resonances at 172.77
and 157.41 ppm of equal intensity were present. The
29Si NMR spectrum of 9 shows three resonances at -6.2,
-10.2, and -13.4 ppm. The two resonances at -10.2
and -13.4 ppm were assigned to the ring silicon atoms
and the peak at -6.2 ppm to the trimethylsilyl silicon
atom. The chemical shifts of 9 are in the range of those
of the other six-membered-ring compounds because the
resonances of the silicon atoms in the 5,6-carboranylene-
1,4-disilacyclohex-2-ene observed so far appear at higher
no. of obsd reflns 6498
5268
4239
(I > 3.00σ(I))
R
0.0545
0.1072
1.083
0.0665
0.1537
0.970
0.0506
0.1316
0.967
Rw
goodness of fit
field (-8 to -16 ppm) than those of the five-membered
4,5-carboranylene-1,3-disilacyclopentane (5 to -4
ppm).10,17 The 13C NMR spectrum of 10 shows two
olefinic resonances at 180.22 and 156.02 ppm. Charac-
teristic low-frequency resonances at 1.08 and -1.44 ppm
(16) (a) Schneider, D.; Werner, H. Angew. Chem., Int. Ed. Engl.
1991, 700. (b) Werner, H.; Baum, M.; Schneider, D.; Windmu¨ller, B.
Organometallics 1994, 13, 1089.
(17) Allen, F. H.; Kennard, O.; Watson, D. G.; Brammer, L.; Orpen,
A. G.; Taylor, R. J . Chem. Soc., Perkin Trans. 1987, 1, 51.

Bis(silyl)nickel Complex
Organometallics, Vol. 19, No. 9, 2000 1725
Sch em e 1
F igu r e 2. X-ray crystal structure of 9 with 50% probability
thermal ellipsoids depicted. Selected bond lengths (Å) and
angles (deg): Si(1)-C(1) 1.905(4), Si(2)-C(2) 1.910(4),
C(1)-C(2) 1.677(6), Si(1)-C(4) 1.885(5), Si(2)-C(3) 1.869-
(4), C(3)-C(4) 1.366(6), C(3)-Si(3) 1.919(5), C(14)-C(10)
1.516, Si(1)-C(1)-C(2) 119.8(3), C(1)-C(2)-Si(2) 121.2(3)
C(2)-Si(2)-C(3) 113.33(19), Si(2)-C(3)-C(4) 123.2(3), C(3)-
C(4)-Si(1) 130.3(3), C(4)-Si(1)-C(1) 111.28(18).
In contrast to the nickel-catalyzed double silylation
reactions of the above alkynes, when dimethyl acety-
lenedicarboxylate was employed as the alkyne in the
nickel-catalyzed reaction of 1 at 80 °C, the alkyne cy-
clotrimerization product was isolated in a quantitative
yield. However, the reaction of the nickel intermediate
with dimethyl acetylenedicarboxylate under mild condi-
tions (0 °C) gave the six-membered-ring compound 11
in 57% yield, together with the cyclotrimerization
in the 29Si NMR of 10 provide evidence for the five-
membered-ring structure. The formation of 10 involves
a 1,2-trimethylsilyl shift during the reaction via an
oxidative addition reaction of a Si-C bond to the inter-
mediate. Such a trimethylsilyl shift has been observed
in the reaction of chloro(triisopropylphosphine)rho-
dium(I) with trimethylsilyl-substituted alkynes16 and in
the nickel-catalyzed reaction of 3,4-benzo-1,1,2,2,-tet-
raethyl-1,2-disilacyclobut-3-ene with silyl-substituted
alkynes.5a
1
product (entry 8). H, 13C, and 29Si NMR spectra for 11
were identical with those of an authentic sample.15
A
similar stoichiometric reaction of the nickel intermedi-
ate 2 with bis(trimethylsilyl)acetylene afforded two
products, 5,6-carboranylene-1,1,4,4-tetramethyl-2,3-bis-
(trimethylsilyl)1,4-disilacyclohex-2-ene (12) and 4,5-
carboranylene-1,1,3,3-tetramethyl-2-[bis(trimethylsilyl)-
methylene]-1,3-disilacyclopentane (13), in 66% and ∼6%
yield, respectively. All spectral data for 12 and 13
support the proposed structures. In particular, the 29Si
NMR chemical shift of -9.98 and -11.02 ppm for 12
resembles the values reported for the six-membered-
ring compounds.15 In contrast, the 29Si NMR of 13 shows
two resonances at 1.74 and 0.87 ppm, clearly indicating
that product 13 is a five-membered-ring compound.
Such a trimethylsilyl shift has been observed in the
nickel-catalyzed reaction.19
Although all the spectra of 3-10 are consistent with
the proposed formulations, this does not provide an
unambiguous proof of structure. Accordingly, a single-
crystal X-ray diffraction study of the 1-phenyl-2-(trim-
ethylsilyl)acetylene insertion product 9 was undertaken.
The molecule structure of 9 is shown in Figure 2. A
summary of data collection parameters is included in
Table 3. The X-ray crystal structure of 9 confirmed the
presence of a six-membered-ring compound comprising
a carboranylene, two silicon atoms, and an unsaturated
hydrocarbon fragment with a CdC bond. An interesting
structural feature of 9 is that the two planes consisting
of Si1, Cl, C2, Si2 and Si2, C3, C4, Si1 are slightly bent
(165.4°). The C3-C4 bond length (1.366(6) Å) is slightly
longer than the typical value for the carbon-carbon
double bond (1.317 Å)17 and that of 5,6-carboranylene-
1,1,4,4-tetramethyl-2,3-diphenyl-1,4-disilacyclohex-2-
ene (1.33(1) Å)15 and the tricyclic product (1.346(3) Å)
formed in the reaction between diphenylacetylene and
tetrakis(dimethylsilyl)benzene.18 The bond lengthening
of C3-C4 may be related to the wideness of the Si2-
C3-C4 bond angle (123.2(3)°), resulting in the dimin-
ishment of the s character of the C4 atom.
Ishikawa and co-workers19 have recently suggested
the mechanistic pathways in the nickel-catalyzed reac-
tion of 3,4-benzo-1,1,2,2-tetraethyl-1,2-disilacyclobut-3-
ene with disubstituted acetylenes. Therefore, the for-
mation of six- and five-membered disilylene ring
compounds may be explained by a series of steps, as
shown in Scheme 1.
(18) Uchimaru, Y.; Brandl, P.; Tanaka, M. J . Chem. Soc., Chem.
Commun. 1993, 744.
(19) (a) Naka, A.; Hayashi, M.; Okazaki, S.; Kunai, A.; Ishikawa,
M. Organometallics 1996, 15, 1101. (b) Ishikawa, M.; Nomura, Y.;
Tozaki, E.; Kunai, A.; Ohshita, J . J . Organomet. Chem. 1990, 399,
205.

1726 Organometallics, Vol. 19, No. 9, 2000
Kang et al.
carbon-carbon bond (1.317 Å) and comparable to that
of 5,6-carboranylene-1,1,4,4-tetramethyl-2,3-diphenyl-
1,4-disilacyclohex-2-ene (1.33(1) Å).15
Nick el-Ca ta lyzed Rea ction w ith Alk en es. The
disilanickela complex 2 is an effective catalyst for the
double silylation of some alkenes. Thus, reaction of 1
with 2 equiv of 4-vinylanisole in the presence of a
catalytic amount of 2 afforded a moderate yield of the
five-membered disilylene compound 15 (entry 11). A
similar reaction of 1 with 1-octene also gave a five-
membered disilylene ring compound 16 as a colorless
liquid. However, treatment of 1 with 1.2 equiv of 1,1-
diphenylethylene in the presence of a catalytic amount
of 2 gave five-membered disilylene ring compound 17,
which contained a saturated side chain in 74% yield
(entry 13). The formulation of 17 was confirmed by
spectrometric analysis. The mass spectrum of the
product showed a molecular ion at m/z 438. Two
1
characteristic doublets at 3.93 and 1.81 ppm in the H
NMR spectrum of 17 are assigned to the two methine
protons. A large coupling constant (J HH ) 13.19 Hz)
indicates that the two methine protons are in a trans
configuration due to the steric hindrance of the phenyl
groups. A low-frequency 13C NMR resonance at 22.68
ppm provides evidence for the tethered carbon atom of
the silicon moieties. The value is comparable to that
observed for cis-4,5-benzo-1,1,3-triethyl-2-methyl-1,3-
disilacyclopent-4-ene.20 Its 29Si NMR spectrum reveals
two resonances at -0.48 and -3.42 ppm due to two
nonequivalent silicon atoms. These results are wholly
consistent with the proposed structure.
F igu r e 3. X-ray crystal structure of 14 with 50% prob-
ability thermal ellipsoids depicted. Selected bond lengths
(Å) and angles (deg): C(1)-C(2) 1.685(4), C(1)-Si(1) 1.919-
(3), Si(1)-C(3) 1.870(3), C(3)-Si(2) 1.870(3), Si(2)-C(2)
1.904(3), C(3)-C(8) 1.354(4), Si(1)-C(1)-C(2) 112.55(18),
C(1)-C(2)-Si(2) 111.98(18), C(2)-Si(2)-C(3) 100.10(12),
Si(1)-C(3)-Si(2) 113.85(14), Si(1)-C(3)-C(8) 130.3(2), Si-
(2)-C(3)-C(8) 115.6(2), C(3)-C(8)-C(9) 130.2(3).
The formation of 14 in the reaction with styrene and
17 in the reaction with 1,1-diphenylethylene can be
rationalized in terms of steric factors. As indicated in
the crystal structure of 14, the bond angle of C3-C8-
C9 is 130.2(3)° and the phenyl ring lies in the plane
Si1-C3-C8-C9 in a horizontal configuration. The
reaction of 1 with 1,1-diphenylethylene then must have
given 17 by intramolecular hydrosilylation due to the
steric hindrance of the two phenyl groups. The routes
to 14 and 17 may have in common an initial oxidative
addition reaction of an olefinic C-H bond to the nickel
center E, followed by the shift of a phenylethyl group
from the nickel atom to one of two silicon atoms (F ), as
shown in Scheme 2. Another olefinic C-H oxidative
addition followed by elimination of nickel dihydride then
could lead to compound 14. On the other hand, when R
) Ph in F , such a second C-H oxidative addition may
not be possible and an intramolecular hydrosilylation
takes place instead, leading to compound 17. We
emphasize that these suggested reaction courses have
no experimental support and are entirely speculative.
The nickel-catalyzed reaction of 1 with 2,3-dimeth-
ylbutadiene afforded 7,8-carboranylene-1,1,6,6-tetram-
ethyl-3,4-dimethyl-1,6-disilacycloocta-3-ene 18 via an
addition reaction in 84% yield (entry 14). The elemental
analysis and mass spectrum of 18 were consistent with
In the first stage, the intermediate 2 coordinates to
an alkyne (A). This is followed by insertion of the triple
bond into a Ni-Si bond to give a seven-membered
intermediate (B) or by oxidative addition of the Si-C
bond to a nickel center (C). Reductive elimination of the
nickel fragment from intermediate B leads to the six-
membered disilylene ring compound. On the other hand,
formation of the five-membered disilylene ring com-
pound may be explained in terms of a shift of trimeth-
ylsilyl groups to the CR carbon atom, giving a (vi-
nylidene)nickel intermediate (D).
The disilanickela compound 2 is not effective in the
nickel-catalyzed double silylation reaction with styrene.
However, the stoichiometric reaction of 2 with styrene
afforded 4,5-carboranylene-1,1,3,3-tetramethyl-2-phe-
nylmethylene-1,3-disilacyclopentane (14) in 76% yield
1
(entry 10). A key feature in the H NMR spectrum of
14 includes a singlet at 7.71 ppm assigned to the vinyl
proton. A characteristic low-frequency 13C NMR reso-
nance at 139.75 ppm provides evidence for a tethered
carbon atom of the two silicon moieties. The 29Si NMR
spectrum of 14 shows two resonances at 4.32 and 0.42
ppm, which are consistent with our prior observation
with the five-membered disilylene ring compounds.
Unambiguous confirmation was provided by an X-ray
crystallographic analysis of 14. The molecular structure
of 14 is shown in Figure 3. The molecule contains one
C2Si2C five-membered ring comprising a carboranylene,
two silicon atoms, and an unsaturated carbon fragment
containing a CdC bond. The C3-C8 bond length (1.354-
(4) Å) is slightly longer than the typical value for the
1
the foumula C12H32B10Si2. The H NMR spectrum of 18
shows a single resonance at δ 1.56, attributed to methyl
protons on carbon, as well as two resonances due to
methyl protons on silicon which show the presence of
two nonequivalent methyl protons. Its 13C NMR spec-
(20) Ishikawa, M.; Naka, A.; Ohshita, J . Organometallics 1993, 12,
4987.

Bis(silyl)nickel Complex
Sch em e 2
Organometallics, Vol. 19, No. 9, 2000 1727
The alkynes and alkenes were purchased from Aldrich. 1,2-
Bis(dimethylsilyl)carborane10 and Ni(PEt3)4 were prepared
22
according to the known procedures.
Me2Si(1,2-C2B10H10)SiMe2Ni(P Et3)2 (2). 1,2-Bis(dimeth-
ylsilyl)carborane 1 (0.48 g, 1.85 mmol) in 20 mL of pentane
was added to a stirred solution of Ni(PEt3)4 (0.98 g, 1.85 mmol)
in 20 mL of pentane at -20 °C. The solution was warmed to
room temperature for 2 h and then was filtered. The residue
was dissolved in toluene (20 mL), and this solution was layered
with pentane (20 mL) at -15 °C. Dark red crystals of 2 were
formed over a period of several days (0.88 g, 86% yield).
Compound 2 remained unchange when kept for 3 days in an
inert atmosphere at room temperature. 1H NMR (C6D6): δ 1.13
(dq, 12H, J HH ) 5.6 Hz, J HP ) 6.4 Hz, CH2), 0.63 (dt, 18H, J HH
) 5.6 Hz, J HP ) 14.2 Hz, CH3), 0.42(s, 12H, SiCH3). 13C{1H}
NMR (C6D6): δ 71.08, 17.05 (d, J CP ) 16.64 Hz, CH2), 6.74 (s,
CH3), 4.11 (s, SiCH3). 31P{1H} NMR (C6D6): δ 5.58. 29Si NMR-
(C6D6): δ 43.19 (t, J SiP ) 40.11 Hz). MS m/z 553 [M+]. Anal.
Calcd for C18H52B10NiP2Si2: C, 39.11; H, 9.40. Found: C, 38.84;
H, 9.22.
Nick el-Ca ta lyzed Rea ction of 1 w ith Va r iou s Alk yn es.
Gen er a l P r oced u r e. Compounds 3-10 were prepared by the
reaction of 1 with the corresponding alkyne in the presence of
a catalytic amount of 2. In a typical synthesis, a mixture of
0.09 g (0.51 mmol) of diphenylacetylene, 0.12 g (0.46 mmol) of
1, and 0.01 g (0.018 mmol) of 2 in toluene (20 mL) was stirred
at room temperature for 12 h. The mixture was filtered
through a short silica gel column to remove the nickel species
from the reaction mixture. The solvent was then removed and
chromatography using benzene/hexane (1:1) as eluent followed.
Recrystallization from hexane at -20 to -10 °C afforded 5,6-
carboranylene-1,1,4,4-tetramethyl-2,3-diphenyl-1,4-disilacyclo-
hex-2-ene (0.17 g, 76% yield). All spectral data for 3-5 and 7
were identical with their authentic samples.15
(i) 6 fr om th e Rea ction w ith 1-P h en yl-1-p r op yn e. Mp:
188 °C. 1H NMR (CDCl3): δ 7.33-6.81 (m, 5H, Ph), 1.56 (s,
3H, C-CH3), 0.39 (s, 6H, Si-CH3), 0.17 (s, 6H, Si-CH3). 13C-
{1H} NMR(CDCl3): δ 160.82 (CPh), 157.04 (CMe), 128.59,
127.39, 126.42 (Ph), 19.71 (C-CH3), -1.41 (Si-CH3), -1.86
(Si-CH3). 29Si NMR (CDCl3): δ -8.92, -10.34. MS: m/z 374
[M+]. Anal. Calcd for C15H30B10Si2: C, 48.11; H, 8.01. Found:
C, 47.87; H, 7.93.
(ii) 8 fr om th e Rea ction w ith 1-Hexyn e. 1H NMR
(CDCl3): δ 6.24 (s, 1H, dCH), 2.17 (t, 2H, J HH ) 9.4 Hz, CCH2),
1.57-1.24 (m, 4H, CH2), 0.92 (t, 3H, J HH ) 4.4 Hz, CH3), 0.33
(s, 6H, Si-CH3), 0.29 (s, 6H, Si-CH3). 13C{1H} NMR (CDCl3):
δ 160.4 (dCH), 138.5 (SiCd), 40.1, 31.7, 23.3, 14.9, -0.04 (Si-
CH3), -0.49 (Si-CH3). 29Si NMR (CDCl3): δ 4.42, 0.92. MS:
m/z 340 [M+]. Anal. Calcd for C12H32B10Si2: C, 42.34; H, 9.40.
Found: C, 42.02; H, 9.24.
(iii) 9 a n d 10 fr om th e Rea ction w ith 1-P h en yl-2-
(tr im eth ylsilyl)a cetylen e. For 9: mp 118-120 °C. 1H NMR
(CDCl3): δ 7.25-6.82 (m, 5H, Ph), 0.50 (s, 6H, Si-CH3), 0.13
(s, 6H, Si-CH3), -0.21 (s, 9H, Si-CH3). 13C{1H} NMR
(CDCl3): δ 172.77 (dCPh), 157.41 (dCSiMe3), 145.95, 128.33,
126.94, 126.76 (Ph), 68.15, 66.67 (carborane carbons), 2.42,
1.44, -0.92. 29Si NMR (CDCl3): δ -6.2, -10.2, -13.4. MS: m/z
432 [M+], 417 [M+ - CH3]. Anal. Calcd for C17H36B10Si3: C,
47.20; H, 8.32. Found: C, 46.85; H, 8.09. For 10: mp 110-
112 °C. 1H NMR (CDCl3): δ 7.22-6.76 (m, 5H, Ph), 0.54 (s,
6H, Si-CH3), 0.18 (s, 6H, Si-CH3), -0.08 (s, 9H, Si-CH3).
13C{1H} NMR (CDCl3): δ 180.22, 156.02 (olefinic carbons),
145.22, 129.58, 127.22, 126.92 (Ph), 4.42, 1.42, 0.12. 29Si NMR
(CDCl3): δ 2.82, 1.08. -1.44. Anal. Calcd for C17H36B10Si3: C,
47.20; H, 8.32. Found: C, 46.72; H, 8.13.
trum consists of three lines at δ 21.19, -0.41, and -0.86.
The value of δ 21.19 is assigned to C-CH3 and two
higher values of δ -0.41 and -0.86 assigned to Si-CH3.
These spectral features are wholly consistent with the
proposed structure of 18. The formation of 18 may be
interpreted in terms of initial activation of a terminal
olefinic C-H bond by the nickel species followed by a
1,4-addition reaction. Such a 1,4-addition has been
observed in the Ni-, Pd-, and Pt-mediated cycloaddition
reactions of disilabutenes to conjugated dienes.21
Exp er im en ta l Section
All experiments were performed under a nitrogen atmo-
sphere in a Vacuum Atmospheres drybox or by standard
Schlenk techniques. Benzene, diethyl ether, toluene, and THF
were freshly distilled from sodium benzophenone. Dichlo-
romethane and hexane were dried and distilled from CaH2.
1H, 13C, and 31P NMR spectra were recorded on a Varian
Gemini 200 spectrometer operating at 200.1, 50.3, and 80.9
MHz, respectively. 29Si NMR spectra were recorded on a J EOL
Model EX-270 spectrometer. Chemical shifts are referenced
relative to TMS(1H), benzene-d6 (1H, δ 7.156; 13C{1H}, δ
128.00), and external 85% H3PO4 (31P). IR spectra were
recorded on a Biorad FTS-165 spectrophotometer. Mass spec-
tra were recorded on a high-resolution VG 70-VSEG instru-
ment operating with an electron beam energy of 60 eV for EI
mass spectra, and elemental analyses were performed with a
Carlo Erba Instruments CHNS-O EA 1108 analyzer.
o-Carborane was purchased from the Callery Chemical Co.
and used without purification. The starting materials, Ni(cod)2,
PEt3, and Me2SiHCl, were purchased from Strem Chemicals.
(iv) Rea ction of 2 w ith Dim eth yl Acetylen ed ica r boxy-
la te (11). To a stirred toluene solution (10 mL) of 2 (0.2 g,
0.36 mmol) was added dimethyl acetylenedicarboxylate (0.12
(21) (a) Tsuji, Y.; Lago, R. M.; Tomohiro, S.; Tsuneishi, H. Organo-
metallics 1992, 11, 2353. (b) Tamao, K.; Okazaki, S.; Kumada, M. J .
Organomet. Chem. 1978, 146, 87. (c) Obora, Y.; Tsuji, Y.; Kawamura,
T. Organometallics 1993, 12, 2853. (d) Tanaka, M.; Uchimaru, Y.;
Lautenschlager, H.-J . Organometallics 1991, 10, 16. (e) Matsumoto,
H.; Shono, K.; Wada, A.; Matsubara, I.; Watanabe, H.; Nagai, Y. J .
Organomet. Chem. 1980, 199, 185.
(22) Browning, J .; Cundy, C. S.; Green, M.; Stone, F. G. A. J . Chem.
Soc. A 1969, 20.

1728 Organometallics, Vol. 19, No. 9, 2000
Kang et al.
mL, 1 mmol) at -80 °C. The mixture was warmed to 0 °C and
stirred for 3 h at that temperature. The solvent was removed
in vacuo, and chromatography using ethyl acetate/hexane (1:
9) as eluent followed. Pure 11 was obtained in 55-60% yield.
All spectral data for product 11 were identical with those of
an authentic sample.15
(carborane carbons), 55.53 (O-CH3), -0.69 (Si-CH3), -1.27
(Si-CH3). 29Si NMR (CDCl3): δ 2.64, 0.28. MS: m/z 390 [M+],
375 [M+ - CH3]. Anal. Calcd for C15H30B10OSi2: C, 46.14; H,
7.68. Found: C, 45.76; H, 7.36.
(viii) 16 fr om th e Rea ction w ith 1-Octen e. 1H NMR
(CDCl3): δ 6.78 (t, 1H, J HH ) 13.78 Hz, dCH), 2.19 (q, 2H,
J HH ) 12.14 Hz, CH2), 1.54-1.20 (m, 8H, (CH2)4), 0.88 (t, 3H,
J HH ) 7.82 Hz, CH3), 0.38 (s, 6H, Si-CH3), 0.25 (s, 6H, Si-
CH3). 13C{1H} NMR (CDCl3): δ 162.51, 140.44 (olefinic car-
bons), 36.92, 30.09, 27.40, 27.23, 20.98, 1.47, -2.69 (Si-CH3),
-2.97 (Si-CH3). 29Si NMR (CDCl3): δ 3.82, 0.12. MS: m/z 368
[M+]. Anal. Calcd for C14H36B10Si2: C, 45.64; H, 9.77. Found:
C, 45.18; H, 9.46.
(v) Rea ction of 2 w ith Bis(tr im eth ylsilyl)a cetylen e (12
a n d 13). To a stirred solution (10 mL) of 2 (0.3 g, 0.54 mmol)
was added bis(trimethyl silyl)acetylene (0.32 mL, 1.4 mmol).
The mixture was heated to 80 °C and stirred overnight.
Products 12 and 13 were isolated by chromatography using
benzene/hexane (1:1) as eluent. For 12: mp 114-116 °C. 1H
NMR (CDCl3): δ 0.40 (s, 12H, Si-CH3), 0.27 (s, 18H, Si-CH3).
13C{1H} NMR (CDCl3): δ 168.51 (CdC), -4.37 (Si-CH3), -5.94
(Si-CH3). 29Si NMR (CDCl3): δ -1.86, -9.98, -11.02. MS: m/z
(ix) 18 fr om th e Rea ction w ith 2,3-Dim eth yl-1,3-bu ta -
d ien e. Mp: 149 °C. 1H NMR (CDCl3): δ 1.64 (s, 4H, CH2),
1.56 (s, 6H, CH3), 0.35 (s, 6H, Si-CH3), 0.27 (s, 6H, Si-CH3).
13C{1H} NMR (CDCl3): δ 120.58 (CdC), 74.94 (carborane
carbon), 21.48 (CH2), 21.19 (CH3), -0.41 (Si-CH3), -0.86 (Si-
CH3). 29Si NMR (CDCl3): δ 6.32. MS: m/z 340 [M+], 325 [M+
- CH3]. Anal. Calcd for C12H32B10Si2: C, 42.34; H, 9.40.
Found: C, 41.98; H, 9.24.
413 [M+ - CH3], 342 [M+ - 2CH3]. Anal. Calcd for C14H40B10
-
Si4: C, 39.23; H, 9.33. Found: C, 39.42; H, 9.51. For 13: mp
110 °C. 1H NMR (CDCl3): δ 0.32 (s, 12H, Si-CH3), 0.18 (s,
12H, Si-CH3). 13C{1H} NMR (CDCl3): δ 174.33 (CdC), -0.64
(Si-CH3), -1.74 (Si-CH3). 29Si NMR (CDCl3): δ 1.74, 0.87,
-0.92. Anal. Calcd for
Found: C, 38.82; H, 9.02.
C14H40B10Si4: C, 39.23; H, 9.33.
X-r a y Cr ysta llogr a p h y. Details of the crystal data and a
summary of intensity data collection parameters for 2, 9, and
14 are given in Table 1. A red prism-shaped crystal of
dimensions 0.38 × 0.20 × 0.40 mm of 2 was selected for
structural analysis. Intensity data for 2 were collected using
a Siemens SMART ccd area detector mounted on a Siemens
P4 diffractometer equipped with graphite-monochromated Mo
KR radiation (λ ) 0.71073 Å). The sample was cooled to 153
K. The intensity data were measured as a series of φ oscillation
frames each of 0.4° for 30 s/frame. A colorless crystal of
dimensions 0.4 × 0.4 × 0.5 mm of 9 was mounted at the tip of
a glass fiber. The cell parameters were obtained by least-
squares refinement from 25 reflections in the range 1.9° < θ
< 25.97° measured with graphite-monochromated Mo KR
radiation on Enraf-Nonious CAD-4 diffractometer. X-ray in-
tensity data were collected by the ω-2θ scan method with θ
) 25.97 for the ranges -12 < h < 12, 0 < k < 26, 0 < l < 15.
The cell parameters of 14 were obtained by least-squares
refinement from 25 reflections in the range 2.01° < θ < 25.97°
on Enraf-Nonious CAD-4 diffractometer. X-ray intensity data
were collected by the ω-2θ scan method with θ ) 25.97 for the
ranges 0 < h < 11, 0 < k < 22, -15 < l < 15. The structures
were solved by direct methods and refined by full-matrix least-
squares methods on F2. Hydrogen atom positions were initially
determined by geometry and refined by a riding model. Non-
hydrogen atoms were refined with anisotropic displacement
parameters.
(vi) Rea ction of 2 w ith Styr en e (14). A mixture of 0.2 g
(0.36 mmol) of 2 and 0.07 mL (0.7 mmol) of styrene in toluene
(10 mL) was refluxed overnight. The solvent was removed in
vacuo, and chromatography using benzene/hexane (1:3) as
eluent followed. Recrystallization from hexane at -20 °C
afforded 4,5-carboranylene-1,1,3,3-tetramethyl-2-(phenylmeth-
ylene)-1,3-disilacyclopentane, 14, in 76% yield, mp 116 °C. 1H
NMR (CDCl3): δ 7.71 (s, 1H, HCdC), 7.39-7.24 (m, 5H, Ph),
0.41 (s, 6H, Si-CH3), 0.28 (s, 6H, Si-CH3). 13C{1H} NMR
(CDCl3): δ 159.44, 139.75 (olefinic carbons), 130.19, 129.25,
128.54, 128.46, 127.72 (Ph), 75.04, 72.60 (carborane carbons),
-0.86-1.52 (Si-CH3). 29Si NMR (CDCl3): δ 4.32, 0.42. MS m/z
360 [M+]. Anal. Calcd for C14H28B10Si2: C, 46.65; H, 7.76.
Found: C, 46.24; H, 7.58.
Nick el-Ca ta lyzed Rea ction of 1 w ith Va r iou s Alk en es.
Gen er a l P r oced u r e. Compounds 15-19 were prepared by
the reaction of 1 with the corresponding alkenes in the
presence of a catalytic amount of 2. In a typical reaction, a
mixture of 0.12 g (0.46 mmol) of 1, 0.1 mL (0.55 mmol) of 1,1-
diphenylethylene, and 0.01 g (0.018 mmol) of 2 in toluene (15
mL) was heated to 80 °C and stirred for 12 h. The solvent was
removed in vacuo, and chromatography using benzene/hexane
(1:3) as eluent (Rf ) 0.6) followed. Recrystallization from
hexane (5 mL) at -5 °C afforded 4,5-carboranylene-1,1,3,3-
tetramethyl-2-(diphenylmethyl)-1,3-disilacyclopentane, 17, in
1
74% yield, mp 185-189 °C (dec). H NMR (CDCl3): δ 7.35-
7.15 (m, 10H, Ph), 3.96 (d, 1H, J HH ) 13.19 Hz, CH), 1.82 (d,
1H, J HH ) 13.19 Hz, CH), 0.13 (s, 6H, Si-CH3), -0.08 (s, 6H,
Si-CH3). 13C{1H} NMR (CDCl3): δ 144.93, 128.73, 127.45,
127.15 (Ph), 49.87 (CH), 22.68 (CH), -0.13, -2.92 (Si-CH3).
29Si NMR (CDCl3): δ -0.48, -3.42. MS: m/z 438 [M+]. Anal.
Calcd for C20H34B10Si2: C, 54.78; H, 7.75. Found: C, 54.32; H,
7.50.
(vii) 15 fr om th e Rea ction w ith 4-Vin yla n isole. Mp: 131
°C. 1H NMR (CDCl3): δ 7.61 (s, 1H, HCdC), 7.26-6.87 (m,
4H, Ph), 3.84 (s, 3H, CH3), 0.39 (s, 6H, Si-CH3), 0.33 (s, 6H,
Si-CH3). 13C{1H} NMR (CDCl3): δ 160.74, 159.05 (olefinic
carbons), 136.06, 132.44, 129.72, 114.01 (Ph), 73.35, 72.86
Ack n ow led gm en t. This work was supported by a
grant from KOSEF (1998-2001).
Su p p or tin g In for m a tion Ava ila ble: Tables listing crys-
tallographic information, atomic coordinates and Beq values,
anisotropic thermal parameters, and intramolecular bond
distances, angles, and torsion angles for 2, 9, and 14. This
material is available free of charge via the Internet at
http://pubs.acs.org.
OM990915Q