Nickel-catalyzed double silylation of a variety of carbonyl compounds with 1,2-bis(dimethylsilyl)carborane

Article abstract of DOI:10.1021/om000527k

The nickel-catalyzed reactions of 1,2-bis(dimethylsilyl)carborane 1 with aldehydes such as isobutyraldehyde, trimethylacetaldehyde, hexanal, and benzaldehyde afforded 5,6-carboranylene-2-oxa-1,4-disilacyclohexanes. The dehydrogenative 1,4-double silylation of methacrolein and trans-4-phenyl-3-buten-2-one in the presence of a catalytic amount of Ni-(PEt₃)₄ took place under similar conditions. In contrast, the reaction of 1 with α-methyl-trans-cinnamaldehyde and trans-cinnamaldehyde under the same reaction conditions yielded the insertion compounds formed via insertion of a carbonyl group into each of the C-Si bonds of 1. The reaction of 1 with diphenylketene gave the 1,2-adduct across the carbonyl group. The structures of compounds 8, 11, and 14 were determined by single-crystal X-ray crystallography.

Full text of DOI:10.1021/om000527k

5026
Organometallics 2000, 19, 5026-5031
Nick el-Ca ta lyzed Dou ble Silyla tion of a Va r iety of
Ca r bon yl Com p ou n d s w ith
1,2-Bis(d im eth ylsilyl)ca r bor a n e
Youngjin Kang,† J insik Kim,‡ Young Kun Kong,‡ J ihwa Lee,§ Soon W. Lee,§
Sang Ook Kang,*,† and J aejung Ko*,†
Departments of Chemistry, Korea University, Chochiwon, Chungnam 339-700, Korea,
Kyonggi University, Suwon, Kyonggido, 440-760, Korea, and Sungkyunkwan University,
Natural Science Campus, Suwon, 440-746, Korea
Received J une 21, 2000
The nickel-catalyzed reactions of 1,2-bis(dimethylsilyl)carborane 1 with aldehydes such
as isobutyraldehyde, trimethylacetaldehyde, hexanal, and benzaldehyde afforded 5,6-
carboranylene-2-oxa-1,4-disilacyclohexanes. The dehydrogenative 1,4-double silylation of
methacrolein and trans-4-phenyl-3-buten-2-one in the presence of a catalytic amount of Ni-
(PEt3)4 took place under similar conditions. In contrast, the reaction of 1 with R-methyl-
trans-cinnamaldehyde and trans-cinnamaldehyde under the same reaction conditions yielded
the insertion compounds formed via insertion of a carbonyl group into each of the C-Si
bonds of 1. The reaction of 1 with diphenylketene gave the 1,2-adduct across the carbonyl
group. The structures of compounds 8, 11, and 14 were determined by single-crystal X-ray
crystallography.
In tr od u ction
The double silylation of unsaturated organic sub-
strates catalyzed by group 10 metal complexes is a
useful route to disilyl organic compounds in which two
Si-C bonds are created by the addition of two silicon
units to unsaturated organic substrates such as alkynes,1
alkenes,2 and 1,3-dienes.3 Nickel complexes, in particu-
lar, are excellent catalysts for such reactions of silicon-
containing linear compounds4 and cyclic disilanes.5
Recently, we6 reported the double silylation reactions
of [o-(SiMe2)2C2B10H10]Pt(PPh3)2, A, containing an o-
carboranylene unit with a variety of unsaturated or-
ganic substrates. Interestingly, its reaction with trans-
cinnamaldehyde afforded the insertion compound B
formed through the insertion of a carbonyl ligand into
each of the C-Si bonds. Usually, R,â-unsaturated
ketones undergo double silylation to give 1,4-adducts.7
Recently, Tanaka and co-workers8 reported that a
metal complex catalyzed double silylation of trans-
cinnamaldehyde with o-bis(dimethylsilyl)benzene af-
forded 1,2 and 1,4 adducts C. The peculiar behavior of
the 1,2-bis(dimethylsilyl)carborane 1 has allowed novel
transformations of some carbonyl compounds. The
double silylation of the carbonyl by the cyclic bis(silyl)-
platinum complex was a stoichiometric process and thus
was limited. Accordingly, we have started a systematic
study of the double silylation of carbonyl compounds
catalyzed by a nickel complex. Here we report the double
silylation reactions of carbonyl compounds such as
aldehydes, R,â-unsaturated aldehydes, R,â-unsaturated
ketones, and a ketene with 1,2-bis(dimethylsilyl)carbo-
rane.
† Korea University.
‡ Kyonggi University.
§ Sungkyunkwan University.
(1) (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.; Kamitori, S.; Hirotsu, K.
Organometallics 1985, 4, 2040.
(2) (a) Ishikawa, M.; Okazaki, S.; Naka, A.; Tachibana, A.; Kawau-
chi, S.; Yamabe, T. Organometallics 1995, 14, 114. (b) Ozawa, F.;
Sugawara, M.; Hayashi, T. Organometallics 1994, 13, 3237. (c)
Hayashi, T.; Kobayashi, T.; Kawamoto, A. M.; Yamashita, H.; Tanaka,
M. Organometallics 1990, 9, 280.
(3) (a) Obora, Y.; Tsuji, Y.; Kawamura, T. Organometallics 1993,
12, 2853. (b) Tsuji, Y.; Lago, R. M.; Tomohiro, S.; Tsuneishi, H.
Organometallics 1992, 11, 2353.
(4) (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.
(5) J zang, T.; Lee, C.; Liu, C. S. Organometallics 1988, 7, 1265.
(6) (a) Kang, Y.; Kang, S. O.; Ko, J . Organometallics 1999, 18, 1818.
(b) Kang, Y.; Kang, S. O.; Ko, J . Organometallics 2000, 19, 1216.
Resu lts a n d Discu ssion
Nick el-Ca ta lyzed Rea ction s w ith Ald eh yd es. Al-
though the platinum complex (C2H4)Pt(PPh3)2 is not a
catalyst for the 1,2-double silylation of aldehydes when
1,2-bis(dimethylsilyl)carborane 1 is used, due to its
(7) (a) Hayashi, T.; Matsumoto, Y.; Ito, Y. J . Am. Chem. Soc. 1988,
110, 5579. (b) Tamao, K.; Okazaki, S.; Kumade, M. J . Organomet.
Chem. 1978, 146, 87.
(8) Uchimaru, Y.; Lautenschlager, H.-J .; Wynd, A. J .; Tanaka, M.;
Goto, M. Organometallics 1992, 11, 2639.
10.1021/om000527k CCC: $19.00 © 2000 American Chemical Society
Publication on Web 10/25/2000

Ni-Catalyzed 1,2-Bis(dimethylsilyl)carborane Silylations
Organometallics, Vol. 19, No. 24, 2000 5027
Ta ble 1. Cr ysta l Da ta of Com p ou n d s 8, 11, a n d 14
8
11
14
empirical formula
molecular weight
crystal system
space group
a, Å
C
14H27B10NOSi2
C16H34B10O2Si2
422.71
orthorhombic
P212121
9.105(2)
10.750(2)
26.495
C20H32B10OSi2
452.74
monoclinic
P21/n
14.110(3)
11.228(15)
34.201(6)
97.025(12)
5377.4(16)
8
1.118
1904
0.144
1.91-22.50
ω
7245
389.65
orthorhombic
Aba2
21.704(4)
17.575(3)
11.997(4)
b, Å
c, Å
â, deg
V, Å3
4576(2)
8
2593.3(8)
4
1.083
869
0.148
3.5-50
ω
2581
2028
0.0453
0.1115
1.019
Z value
D
calcd, g cm-3
1.131
1632
0.160
3.5-50
ω
2082
1068
0.0822
0.2009
1.013
F(000)
µ (cm-1
)
λ(Mo KR radiation) (Å)
scan type
no. of reflns measd
no. of obsd reflns I > 2σ(I)
R
6911
0.0458
0.1124
1.018
Rw
goodness of fit
Ta ble 2. Nick el-Ca ta lyzed Rea ction s of Ald eh yd e
w ith 1,2-Bis(d im eth ylsilyl)ca r bor a n e
strong Pt-Si bond strength, the Ni complex Ni(PEt3)4
was found to be a good catalyst for the dehydrogenative
double silylation of aldehydes. The nickel-catalyzed
double silylation can be carried out either by reacting
1 and the aldehyde in the presence of the Ni(PEt3)4
catalyst or by reacting 1 and the aldehyde in the
presence of a catalytic amount of the cyclic bis(silyl)-
nickel complex Me2Si(o-C2B10H10)SiMe2Ni(PEt3)2 2.9
Both procedures showed a high catalytic activity. How-
ever, the former procedure is preferred due to the easy
accessibility of Ni(PEt3)4. The results are summarized
in Table 2.
Isobutyraldehyde readily reacted at 80 °C with 1 in
the presence of a catalytic amount of Ni(PEt3)4 to give
5,6-carboranylene-1,1,4,4-tetramethyl-2-oxa-3-isopropyl-
1,4-disilacyclohexane 3 in 74% yield (eq 1). In a similar
fashion, the nickel-catalyzed reaction of 1 with other
aliphatic aldehydes such as trimethylacetaldehyde,
5-norbornene-2-carboxaldehyde, and hexanal yielded
the corresponding six-membered cyclic insertion prod-
ucts. Benzaldehyde also underwent the 1,2-double si-
lylation reaction under mild conditions. Experiments
utilizing substituted aromatic aldehydes such as 4-cy-
anobenzaldehyde followed a similar course. These reac-
tions of 1 with aromatic aldehydes were faster than
those of aliphatic aldehydes. Such dehydrogenative 1,2-
double silylation reactions have been reported using a
platinum complex as the catalyst with o-bis(dimethyl-
silyl)benzene.8 The insertion of an aldehyde carbonyl
group into the Si-Si bond promoted by fluoride ion was
also noted.10
To provide structural information for one of the newly
prepared compounds, a single-crystal X-ray diffraction
study of the 4-cyanobenzaldehyde addition product 8
was undertaken. The molecular structure of 8 is shown
in Figure 1. A summary of cell constants and data
collection parameters is included in Table 1. The X-ray
crystal structure of 8 confirmed the presence of a six-
membered ring comprising the two carboranylene car-
bon atoms, two silicon atoms, and a C-O fragment. The
heterocyclic ring is best described as a flattened boat
configuration. The Si(1)-O(1) bond length (1.621(7) Å)
and O(1)-C(7) bond length (1.156(10) Å) are slightly
shorter than those in 5,6-benzo-1,1,4,4-tetramethyl-3-
(diphenylmethylidene)-1,4-disila-2-oxa-5-cyclohexene6 and
(9) (a) Kang, Y.; Lee, J .; Kong, Y. K.; Kang, S. O.; Ko, J . Chem.
Commun. 1998, 2343. (b) Kang, Y.; Lee, J .; Kong, Y. K.; Kang, S. O.;
Ko, J . Organometallics 2000, 19, 1722.
(10) Hiyama, T.; Obayashi, M. Tetrahedron Lett. 1983, 24, 4109.

5028 Organometallics, Vol. 19, No. 24, 2000
Kang et al.
Ta ble 3. Nick el-Ca ta lyzed Rea ction s of En on es
w ith 1,2-Bis(d im eth ylsilyl)ca r bor a n e
F igu r e 1. ORTEP drawing of 8 showing the atom-labeling
scheme with 50% probability thermal ellipsoids. Selected
bond lengths (Å) and angles (deg): Si(1)-O(1) 1.621(7),
O(1)-C(7) 1.156(10), Si(2)-C(70) 1.825(10), Si(2)-C(2)
1.902(8), C(1)-C(2) 1.698(10), C(7)-C(8) 1.55(2), N(1)-
C(14) 1.130(2), O(1)-Si(1)-C(1) 105.1(3), Si(1)-C(1)-C(2)
118.5(5), C(1)-C(2)-Si(2) 120.5(5), C(7)-Si(2)-C(2) 105.8-
(4), Si(2)-C(7)-O(1) 125.8(8).
11
comparable to those of Me2SiOReO3 and bis[(8′-(di-
methylamino)naphth-1′-yl)dimethylsilyl]ether.12
The 1H, 13C, and 29Si NMR spectra and the mass
spectra of compounds 3-8 were consistent with the
1
structure determined for 8. The H NMR spectrum of 8
contained a distinguishing low-field methine resonance
(δ 4.79) which was used to monitor its formation. Four
singlets (δ 0.49, 0.44, 0.28, 0.03) in the 1H NMR
spectrum and four singlets (-0.64, -1.68, -2.04, -5.42
ppm) in the 13C NMR spectrum of 8 could be assigned
to the methyl groups on the silicon atoms which
indicated that the methyl groups are not equivalent. The
29Si NMR spectrum of 8 exhibited two resonances at
12.59 and 0.95 ppm arising from the nonequivalent
silicon atoms. Similar nickel-catalyzed reactions of 1
with ketones such as acetone, acetophenone, and pina-
colone afforded a complicated mixture of products which
were difficult to separate in pure form.
silylation of prop-2-enal and methacrolein with 1,2-bis-
(dimethylsilyl)carborane at high temperature. No reac-
tion was observed in all cases when cyclic bis(silyl)-
platinum complex was tried as the catalyst. However,
R,â-unsaturated carbonyl compounds readily reacted
with 1,2-bis(dimethylsilyl)carborane in the presence of
a catalytic amount of Ni(PEt3)4 to give the 1,4-double
silylating products. Thus, reaction of 1 with methac-
rolein in the presence of a catalytic amount of Ni(PEt3)
yielded 7,8-carboranylene-1,1,6,6-tetramethyl-4-methyl-
2-oxa-1,6-disilacyclooct-3-ene (9) in 56% yield (eq 2). The
Ishikawa,13 Tanaka,8 and their co-workers have sug-
gested mechanistic pathways for the nickel- and plati-
num-catalyzed reaction of 3,4-benzo-1,1,2,2-tetraethyl-
1, 2-disilacyclobut-3-ene or o-bis(dimethylsilyl)benzene
with carbonyl compounds. On the basis of their sugges-
tions, a reasonable mechanism for the formation of 3-8
involves the initial formation of bis(silyl)nickel complex
2 as a key intermediate, a species which we had
reported earlier.9 Intermediate 2 then coordinates to a
carbonyl group (D), followed by insertion of the carbonyl
bond into a Ni-Si bond to give a seven-membered cyclic
intermediate (E). Analogous reactions of a silyl-substi-
tuted transition metal complex with carbonyl com-
pounds have been reported previously.8 Reductive elimi-
nation of the nickel fragment from the latter intermediate
then leads to the product (F ).
reaction of 1 with the more hindered trans-4-phenyl-3-
buten-2-one afforded 7,8-carboranylene-1,1,6,6-tetrameth-
yl-3-methyl-5-phenyl-2-oxa-1,6-disilacyclooct-3-ene 10 in
28% yield (Table 3). These products, 9 and 10, could
1
readily be isolated by preparative GLC. The H NMR
spectrum of 9 contains five resonances at 1.56, 0.42,
0.37, 0.35, and 0.33 ppm, assigned to the five kinds of
methyl groups. The four resonances at 0.42, 0.37, 0.35,
and 0.33 ppm were assigned to the methyl groups on
the silicon atoms and the peak at 1.56 ppm to the
methyl group on the olefinic carbon atom. In the olefinic
region of the 13C NMR spectrum of 9, two resonances
at 136.03 and 107.22 ppm are present. The 29Si NMR
spectrum of 9 shows two resonances at 16.42 and -1.36
ppm. The chemical shifts of 9 are in the range of those
of the other eight-membered ring compounds. The
structure of 10 was further indirectly confirmed by the
Nick el-Ca ta lyzed Rea ction w ith r,â-Un sa tu r a ted
Ald eh yd es a n d Keton es. Since platinum complex
catalyzed 1,4-double silylation of R,â-unsaturated car-
bonyl compounds with disilanes is a known process,8
we attempted the platinum complex catalyzed double
(11) Sheldrick, G. M.; Sheldrick, W. S.; J . Chem. Soc. A 1969, 2160.
(12) Spiniello, M.; White, J . M. Organometallics 2000, 19, 1350.
(13) Ishikawa, M.; Naka, A.; Okazaki, S.; Sakamoto, H. Organome-
tallics 1993, 12, 87.

Ni-Catalyzed 1,2-Bis(dimethylsilyl)carborane Silylations
Organometallics, Vol. 19, No. 24, 2000 5029
rolein, when R-methyl-trans-cinnamaldehyde was em-
ployed in the reaction of 1 under the same conditions,
the insertion product, 12, of a carbonyl group into each
of the C-Si bonds was obtained as a colorless solid in
88% yield (eq 4). A key feature in the 1H NMR spectrum
F igu r e 2. ORTEP drawing of 11 showing the atom-
labeling scheme with 50% probability thermal ellipsoids.
Selected bond lengths (Å) and angles (deg): Si(1)-C(7)
1.893(4), Si(1)-C(2) 1.939(4), C(7)-C(8) 1.529(6), C(8)-C(9)
1.501(6), C(9)-O(2) 1.205(5), C(9)-C(10) 1.488(8), Si(2)-
O(1) 1.613(3), Si(2)-C(1) 1.912(4), C(1)-C(2) 1.724(5),
C(1)-Si(2)-O(1) 104.18(18), Si(2)-C(1)-C(2) 123.9(2), C(2)-
Si(1)-C(7) 109.43(16), Si(1)-C(7)-C(8) 113.8(3), C(7)-
C(8)-C(9) 113.3(4), C(8)-C(9)-O(2) 121.0(4), O(2)-C(9)-
C(10) 121.2(5).
of 12 includes a singlet at 5.46 ppm assigned to the
methine, concomitant with the disappearance of the
aldehyde hydrogen peak. trans-Cinnamaldehyde reacted
similarly to give 13. As noted in the Introduction,
platinum complex A had been found6 to react with trans-
cinnamaldehyde to give a product (B) in which a CdO
bond had inserted into both of the C-Si bonds. The
spectral data for 13 were identical to those we had
observed for compound A. It is of interest that in the
case of compound A it had been proven that the oxygen
atom of the disiloxane unit was derived from the
aldehyde.6 Similar insertion was observed in the reac-
crystal structure of 11, the hydrolysis product of 10 (eq
3). Such 1,4-double silylation has been observed in the
tions of (CO)FeSiMe2CH2CH2SiMe2,17 (CO)5MnSiMe3,18
and MeEt2SiCo(CO)3L19 with benzaldehyde and of 3,4-
benzo-1,1,2,2-tetraethyldisilacyclobut-3-ene with ben-
zophenone in cyclohexene.
Such an insertion of the carbonyl functionality into
the o-carborane C-H bond was observed in Yamamoto’s
work on the chemoselective addition of o-carborane to
aldehyde groups20 or in the fluoride-promoted reaction
of o-carborane with aldehydes.21
transition metal catalyzed double silylation of R,â-
unsaturated ketones and aldehydes by Ito,14 Kumada,15
Ishkawa,16 and their respective co-workers. The product
10 is sensitive to hydrolysis; when crystal growth of 10
was attempted, it was 11 which was isolated. In a
subsequent experiment, treatment of 10 with 2 equiv
of H2O in benzene-d6 was monitored by 1H NMR
spectroscopy. The disappearance of the olefinic hydrogen
peak at 6.36 ppm and the formation of a new methylene
signal at 2.55 ppm and a hydroxy signal at 2.16 ppm
were noted. The 1H NMR spectrum of the product
exhibited four resonances at 0.32, 0.22, 0.21, and 0.07
ppm due to the methyl groups on silicon. The IR
spectrum of the compound showed new absorptions due
to the carbonyl stretch at 1683 cm-1 and νOH stretch at
3205 cm-1, concomitant with the disappearance of the
C-O stretching mode at 987 cm-1. The mass spectrum
of the product showed a molecular ion at m/z 422. The
molecular structure of 11 as determined by a single-
crystal X-ray diffraction study is shown in Figure 2. The
crystallographic data are given in Table 1.
Diphenylketene also underwent dehydrogenative
double silylation with 1 (eq 5) and the product, 1,2-
adduct to the carbonyl group, was obtained in 80% yield.
The initial indication of the cyclization to form 14 was
given by the observation of a parent ion in the mass
spectrum at m/z 468. Although the 1H and 13C NMR
spectra of 14 supported the proposed structure, unam-
biguous confirmation was provided by an X-ray crystal-
lographic analysis. The molecular structure of 14 is
shown in Figure 3. The molecule contains one C2Si2CO
six-membered ring comprising two carboranylene car-
The 1,4-double silylation reactions are quite sensitive
to the substituents on the CdO group. In contrast to
the 1,4-double silylation reactions of 1 with methac-
(17) Nakazawa, H.; J ohnson, D. L.; Gladysz, J . A. Organometallics
1983, 2, 1846.
(18) (a) J ohnson, D. L.; Gladysz, J . A. J . Am. Chem. Soc. 1979, 101,
6433. (b) J ohnson, D. L.; Gladysz, J . A. Inorg. Chem. 1981, 20, 2508.
(19) Murai, S.; Kato, T.; Sonoda, N.; Seki, Y.; Kawamoto, K. Angew.
Chem., Int. Ed. Engl. 1979, 18, 393.
(20) Nakamura, H.; Aoyagi, K.; Yamamoto, Y. J . Org. Chem. 1997,
62, 780.
(21) (a) Cai, J .; Nemoto, H.; Nakamura, H.; Singaram, B.; Yama-
moto, Y. Chem. Lett. 1996, 792. (b) Nakamura, H.; Aoyagi, K.;
Yamamoto, Y. J . Am. Chem. Soc. 1998, 20, 1167.
(14) (a) Hayashi, T.; Matsumoto, Y.; Ito, Y. Tetrahedron Lett. 1988,
29, 4147. (b) Hayashi, T.; Matsumoto, Y.; Ito, Y. J . Am. Chem. Soc.
1988, 110, 5579.
(15) Tamao, K.; Okazaki, S.; Kumada, M. J . Organomet. Chem.
1978, 146, 87.
(16) Ishikawa, M.; Sakamoto, H.; Tabuchi, T. Organometallics 1991,
10, 3173.

5030 Organometallics, Vol. 19, No. 24, 2000
Kang et al.
Carborane was purchased from the Callery Chemical Co.
and used without purification. The starting materials, Ni-
(COD)2, PEt3, and ClSiMe2H, were purchased from Strem
Chemicals. All the aldehydes were purchased from Aldrich.
1,2-Bis(dimethylsilyl)carborane and Ni(PEt3)422 were prepared
according to previous described procedures.
Nick el-Ca ta lyzed Rea ction of 1 w ith Va r iou s Ald e-
h yd es. Gen er a l P r oced u r e. Compounds 3-14 were pre-
pared by the reaction of 1 with the corresponding aldehydes
in the presence of a catalytic amount of Ni(PEt3)4. In a typical
synthesis, a mixture of isobutyraldehyde (0.04 mL, 0.43 mmol),
1 (0.09 g, 0.36 mmol), and Ni(PEt3)4 (0.005 g, 0.018 mmol) in
toluene (15 mL) was heated to 80 °C for 12 h. The mixture
was passed through a short silica gel column to remove the
nickel species from the reaction mixture. The solution was
chromatographed using benzene/hexane (1:4) as eluent. Re-
crystallization from ethanol at -10 °C afforded 5,6-carbora-
nylene-1,1,4,4-tetramethyl-3-isopropyl-2-oxa-1,4-disilacyclo-
hexane 3 in 74% yield: mp 82 °C; 1H NMR (CDCl3) δ 3.14 (d,
1H, J HH ) 8.4 Hz, OCH), 1.79 (d, sept, 1H, J HH ) 8.2 Hz, CH),
0.93 (d, 6H, J HH ) 8.2 Hz, CCH3), 0.36 (s, 3H, SiCH3), 0.33 (s,
3H, SiCH3), 0.31 (s, 3H, SiCH3), 0.28 (s, 3H, SiCH3); 13C{1H}
NMR (CDCl3) δ 70.78, 31.86, 19.77, -0.97, -1.10, -3.30,
-5.09; 29Si NMR (CDCl3) δ 11.94, -0.56; MS m/z 330 [M+]; IR
(KBr pellet; cm-1) 2968 (m), 2908 (w), 2602 (s), 1471 (m), 1416
(w), 1382 (w), 1361 (w), 1288 (w), 1258 (s), 1218 (w), 1092 (m),
1076 (m), 1043 (s), 982 (w), 942 (w), 878 (m), 820 (m), 801 (m),
692 (m), 662 (w). Anal. Calcd for C10H30B10OSi2: C, 36.32; H,
9.15. Found: C, 35.94; H, 8.86.
4 fr om th e Rea ction w ith Tr im eth yla ceta ld eh yd e.
Compound 4 was prepared by using the same procedure as
described for 3 in 66% yield. It was purified by sublimation:
mp 123 °C; 1H NMR (CDCl3) δ 3.32 (s, 1H, OCH), 0.90 (s, 9H,
CCH3), 0.38 (s, 3H, SiCH3), 0.37 (s, 3H, SiCH3), 0.35 (s, 3H,
SiCH3), 0.33 (s, 3H, SiCH3); 13C{1H} NMR (CDCl3) δ 74.88,
29.38, 21.45, -0.26, -0.48, -0.92, -1.80; 29Si NMR (CDCl3) δ
11.36, 0.35 ; MS m/z 344 [M+]; IR (KBr pellet; cm-1) 2972 (m),
2911 (w), 2880 (w), 2602 (s), 1476 (w), 1462 (w), 1415 (w), 1400
(w), 1365 (w), 1258 (m), 1202 (w), 1160 (w), 1090 (m), 1076
(m), 1032 (m), 984 (w), 942 (w), 881 (m), 862 (m), 850 (m), 822
(m), 804 (w), 736 (w), 722 (w), 696 (w), 688 (w), 660 (w). Anal.
Calcd for C11H32B10OSi2: C, 38.33; H, 9.35. Found: C, 37.94;
H, 9.06.
F igu r e 3. ORTEP drawing of 14 showing the atom-
labeling scheme with 50% probability thermal ellipsoids.
Selected bond lengths (Å) and angles (deg): Si(1)-O(1)
1.641(2), O(1)-C(7) 1.414(3), C(7)-Si(2) 1.875(3), Si(2)-
C(2) 1.919(3), C(1)-C(2) 1.700(3), C(1)-Si(1) 1.908(3),
C(7)-C(8) 1.335(4), C(7)-O(1)-Si(1) 122.3(2), O(1)-Si(1)-
C(1) 105.11(11), Si(1)-C(1)-C(2) 118.18(18), C(1)-C(2)-
Si(2) 120.39(17), C(2)-Si(2)-C(7) 103.80(11), Si(2)-C(7)-
O(1) 107.46(18), C(7)-O(1)-Si(1) 122.29(16), Si(2)-C(7)-
C(8) 132.5(2), C(7)-C(8)-C(15) 119.6(2), C(9)-C(8)-C915)
115.8(2).
bon atoms, two silicon atoms, and a saturated C-O
fragment. The C2Si2CO ring is described as a tilted boat
configuration. The C7-C8 bond length (1.335(4) Å) is
slightly longer than the typical value for the carbon-
carbon double bond (1.317 Å) and comparable to that
in 5,6-carboranylene-1,1,4,4-tetramethyl-2,3-diphenyl-
1,4-disilacyclohex-2-ene (1.33(1) Å). The bond lengthen-
ing of C7-C8 may be related to the wideness of the
Si(2)-C(7)-C(8) bond angle (132.5(2)°), resulting in a
diminishing of the s character of the C7 atom. The two
phenyl rings attached to C8 are nearly perpendicular
to one another with a dihedral angle of 86.9°.
In conclusion, the cyclic bis(silyl)nickel complex was
found to be a good catalyst for the double silylation of a
variety of carbonyl compounds. Thus, the nickel-
catalyzed reactions of 1,2-bis(dimethylsilyl)carborane
with aldehydes such as isobutyraldehyde, trimethylace-
taldehyde, hexanal, and benzaldehyde afforded 5,6-
carboranylene-2-oxa-1,4-disilacyclohexane.
The 1,4-double silylation of R,â-unsaturated carbonyl
compounds such as methacrolein and trans-4-phenyl-
3-buten-2-one gave the 1,4-double silylated products. In
contrast, the double silylation reaction of 1 with R-
methyl-trans-cinnamaldehyde and trans-cinnamalde-
hyde yielded products formed by insertion of a carbonyl
group into each of the C-Si bonds of 2. Thus, the cyclic
bis(silyl)nickel complex as a catalyst has been further
exploited in a series of novel chemical transformations.
5 fr om t h e R ea ct ion w it h Hexa n a l. Compound 5 was
prepared by using the same procedure as described for 3 as a
liquid in 38% yield: 1H NMR (CDCl3) δ 3.46 (t, 1H, J HH ) 6.6
Hz, OCH), 1.62-1.22 (m, 8H, CH2), 0.89 (t, 3H, J HH ) 4.3 Hz,
CH3), 0.37 (s, 3H, SiCH3), 0.30 (s, 3H, SiCH3), 0.22 (s, 3H,
SiCH3), 014 (s, 3H, SiCH3); 13C{1H} NMR (CDCl3) δ 77.23,
38.24, 31.82, 28.16, 22.68, 11.14, -0.12, -0.98, -3.10, -6.19;
29Si NMR (CDCl3) δ 13.08, 0.22; MS m/z 358 [M+]. Anal. Calcd
for C12H34B10OSi2: C, 40.19; H, 9.55. Found: C, 39.79; H, 9.22.
6 fr om th e Rea ction w ith 5-Nor bor n en e-2-ca r boxa l-
d eh yd e. Compound 6 was prepared by using the same
procedure as described for 3 in 83% yield: mp 168 °C; 1H NMR
(CDCl3) δ 6.18 (dd, 1H, J HH ) 8.40 Hz, J HH ) 1.04 Hz), 5.83
Exp er im en ta l Section
(dd, 1H, J HH ) 8.40 Hz, J HH ) 1.04 Hz), 3.41 (d, 1H, J HH
)
4.08 Hz, OCH), 2.17 (s, 2H, CH2), 1.94-1.05 (m, 5H), 0.33 (s,
9H, SiCH3), 0.31 (s, 3H, SiCH3), 0.28 (s, 3H, SiCH3), 0.25 (s,
3H, SiCH3); 13C{1H} NMR (CDCl3) δ 138.42, 131.95 (CdCH),
77.03 (OCH), 52.68, 43.51, 41.92, 39.27, 36.77, -0.97 (Si-CH3),
-1.39 (Si-CH3), -3.06 (Si-CH3), -5.76 (Si-CH3); MS m/z 380
[M+]; IR (KBr pellet; cm-1) 3072 (m), 2954 (s), 2877 (m), 2598
(s), 1448 (w), 1402 (w), 1257 (s), 1087 (m), 1022 (s,br), 983 (w),
942 (w), 908 (w), 870 (m), 822 (s), 802 (w), 744 (w), 682 (w).
Anal. Calcd for C14H32B10OSi2: C, 44.20; H, 8.41. Found: C,
43.94; H, 8.22.
All experiments were performed under a nitrogen atmos-
phere in a Vacuum Atmospheres drybox or by standard
Schlenk techniques. Benzene, toluene, and THF were distilled
from sodium benzophenone. Dichloromethane and hexane
were distilled over CaH2. EtOH was distilled over Linde type
1
4 Å molecular sieves. H and 13C NMR spectra were recorded
on a Varian Gemini 200 spectrometer operating at 200.1 and
50.3 MHz, respectively. 29Si NMR spectra were recorded on a
J EOL model EX-270 spectrometer. Chemical shifts were
referenced relative to TMS. IR spectra were recorded on a
Biorad FTS-165 spectrometer. Mass spectra were recorded on
a Shimadzu model QP-1000 spectrometer, and elemental
analyses were performed with a Carlo Erba Instruments
CHNS-O EA 1108 analyzer.
7 fr om th e r ea ction w ith ben za ld eh yd e: mp 146 °C; 1H
NMR (CDCl3) δ 7.37-7.12 (m, 5H, Ph), 4.74 (s, 1H, OCH), 0.47
(22) Browning, J .; Cundy, C. S.; Green, M.; Stone, F. G. A. J . Chem.
Soc. A 1969, 20.

Ni-Catalyzed 1,2-Bis(dimethylsilyl)carborane Silylations
Organometallics, Vol. 19, No. 24, 2000 5031
(s, 3H, SiCH3), 0.43 (s, 3H, SiCH3), 0.25 (s, 3H, SiCH3), 0.06
(s, 3H, SiCH3); 13C{1H} NMR (CDCl3) δ 139.61, 128.91, 127.85,
126.89, 126.73, 124.61, 67.86, -0.91, -2.78, -3.78, -6.48; 29Si
NMR (CDCl3) δ 10.46, -0.72; MS m/z 364 [M+]; IR (KBr pellet;
cm-1) 30 (62 (w), 3035 (w), 2924 (m), 2852 (w), 2602 (s), 1494
(w), 1450 (w), 1402 (w), 1258 (s), 1162 (w), 1086 (m), 1078 (m),
1040 (m), 1022 (m), 982 (w), 962 (w), 918 (w), 878 (m), 870
(m), 838 (m), 820 (m), 792 (w), 770 (w), 721 (w), 629 (w), 662
(w). Anal. Calcd for C13H28B10OSi2: C, 42.85; H, 7.68. Found:
C, 42.41; H, 7.88.
8 fr om th e r ea ction w ith 4-cya n oben za ld eh yd e: mp 173
°C; 1H NMR (CDCl3) δ 7.64-7.23 (m, 4H, Ph), 4.79 (s, 1H,
OCH), 0.49 (s, 3H, SiCH3), 0.44 (s, 3H, SiCH3), 0.28 (s, 3H,
SiCH3), 0.03 (s, 3H, SiCH3); 13C{1H} (NMR (CDCl3) δ 217.74,
137.27, 129.32, 128.77, 127.45, 127.04, 126.82, 68.04, -0.64,
-1.68, -2.04, -5.42; 29Si NMR (CDCl3) δ 12.59, 0.95; MS m/z
390 [M+]; IR (KBr pellet; cm-1) 3046 (w), 2968 (w), 2918 (w),
2852 (w), 2596 (s), 2238 (m), 1604 (m), 1498 (m), 1408 (w),
1335 (w), 1258 (s), 1204 (w), 1108 (w), 1084 (m), 1061 (s), 1020
(w), 982 (w), 882 (s), 863 (s), 832 (s), 805 (w), 764 (m), 722 (w),
procedure as described for 3. The product was isolated by
chromatography using benzene/hexane (1:9) as eluent in 88%
yield: mp 158 °C; 1H NMR (CDCl3) δ 7.47-7.18 (m, 10H, Ph),
6.54 (d, 2H, J HH ) 1.4 Hz, CH)), 5.46 (d, 1H, J HH ) 1.4 Hz,
CHO), 1.96 (s, 6H, dCCH3), 0.27 (s, 6H, Si-CH3), 0.08 (s, 6H,
Si-CH3); 13C{1H} NMR (CDCl3) δ 136.82, 136.59, 131.80,
129.22, 129.15, 128.45, 127.41, 71.22, 14.58, 1.17, -0.67; 29Si
NMR (CDCl3) δ 13.6; MS(EI) m/z 566 [M+]; IR (KBr pellet;
cm-1) 3088 (w), 3055 (w), 3042 (w), 2968 (m), 2625 (s), 1598
(w), 1479 (w), 1442 (w), 1365 (m), 1261 (s), 1182 (w), 1092 (s),
1048 (s), 1030 (s), 954 (w), 918 (m), 892 (m), 808 (s), 782 (m),
722 (m), 666 (w). Anal. Calcd for C26H42B10O3Si2: C, 55.12; H,
7.41. Found: C, 54.88; H, 7.28.
13 fr om th e Rea ction w ith tr a n s-Cin n a m a ld eh yd e.
Compound 13 was prepared by using the same procedure as
described for 3. The product was isolated by chromatography
using benzene/hexane (1:9) as eluent in 53% yield: mp 56 °C;
1H NMR (CDCl3) δ 7.52-6.18 (m, 10H, Ph), 6.88 (dd, 2H, J HH
) 12.3 Hz, J HH ) 5.8 Hz, dCH), 6.74 (dd, 2H, J HH ) 12.3 Hz,
J HH ) 4.4 Hz, dCH), 4.89 (dd, 2H, J HH ) 5.8 Hz, J HH ) 4.4
Hz, CH), 0.23 (s, 6H, Si-CH3), 0.11 (s, 6H, Si-CH3); 13C{1H}
NMR (CDCl3) δ 162.2, 156.6, 137.4, 133.6, 132.1, 129.1, 128.7,
31.1, -0.46 (Si-CH3), -0.68 (Si-CH3); 29Si NMR (CDCl3) δ
17.4; MS(EI) m/z 538 [M+]; Anal. Calcd for C24H38B10O3Si2: C,
53.52; H, 7.05. Found: C, 53.22; H, 6.83.
682 (w), 664 (w), 652 (w), 562 (m). Anal. Calcd for C14H27B10
NOSi2: C, 43.18; H, 6.93. Found: C, 43.52; H, 7.08.
-
9 fr om th e r eaction with m eth acr olein : 1H NMR (CDCl3)
δ 6.01 (t, 1H, J HH ) 2.4 Hz, OCH), 1.65 (d, 2H, J HH ) 2.4 Hz,
CH2), 1.56 (s, 3H, CCH3), 0.42 (s, 3H, SiCH3), 0.37 (s, 3H,
SiCH3), 0.35 (s, 3H, SiCH3), 0.33 (s, 3H, SiCH3); 13C{1H} NMR
(CDCl3) δ 136.03, 107.22, 22.70, 18.38, -0.64, -1.09, -2.54,
-2.94; 29Si NMR (CDCl3) δ 16.42, -1.36; MS m/z 328 [M+]; IR
(KBr pellet; cm-1) 2968 (m), 2938 (w), 2855 (w), 2602 (s), 1678
(w), 1455 (w), 1258 (s), 1172 (s), 1136 (w), 1082 (s), 1072 (w),
1042 (s), 864 (w), 850 (w), 822 (br), 802 (s). Anal. Calcd for
14 fr om th e Rea ction w ith Dip h en ylk eten e. Compound
14 was prepared by using the same procedure as described
for 3. The product was isolated by chromatography using
benzene/hexane (1:1) as eluent in 80% yield: mp 98 °C; 1H
NMR (CDCl3) δ 7.44-7.12 (m, 10H, Ph), 0.19 (s, 6H, Si-CH3),
-0.02 (s, 6H, Si-CH3); 13C{1H} NMR (CDCl3) δ 143.28, 141.18,
136.25, 130.57, 129.24, 128.45, 128.36, 128.25, 127.95, 127.68,
127.43, 127.28, 71.53, -1/26, -1.53; 29Si NMR (CDCl3) δ 11.97,
-6.47; MS(EI) m/z 468 [M+]; IR (KBr pellet; cm-1) 3001 (w),
2950 (w), 2925 (m), 2600 (s), 1460 (m), 1260 (s), 1080 (m), 950
(m), 860 (m), 710 (w). Anal. Calcd for C20H32B10OSi2: C, 53.09;
H, 5.90. Found: C, 52.86; H, 5.72.
C
10H28B10OSi2: C, 36.58; H, 8.53. Found: C, 36.32; H, 8.38.
10 fr om th e r ea ction w ith tr a n s-4-p h en yl-3-bu tyn -2-
1
on e: mp 145 °C; H NMR (CDCl3) δ 7.43-7.18 (m, 5H, Ph),
6.36 (d, 1H, J HH ) 9.6 Hz, dCH), 2.11 (d, 1H, J HH ) 9.6 Hz,
CHPh), 1.53 (s, 3H, CCH3), 0.45 (s, 3H, SiCH3), 0.43 (s, 3H,
SiCH3), 0.33 (s, 3H, SiCH3), 0.25 (s, 3H, SiCH3); 13C{1H} NMR
(CDCl3) δ 207.17, 136.99, 134.51, 128.87, 128.55, 127.68,
126.75, 126.48, 71.65, 29.93, 26.03, 1.76, 1.25, 0.58, -2.17; 29Si
NMR (CDCl3) δ 24.72, 6.24; MS m/z 404 [M+]; IR (KBr pellet;
cm-1) 3026 (w), 2971 (m), 2932 (s), 2854 (s), 2602 (s), 1598 (w),
1492 (w), 1462 (m), 1442 (w), 1260 (m), 1182 (m), 1104 (m),
1092 (m), 1036 (w), 987 (s), 962 (m), 862 (m), 823 (m), 722
(m). Anal. Calcd for C16H32B10O Si2: C, 47.51; H, 7.91. Found:
C, 47.34; H, 7.68.
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 8, 11, and
14 are given in Table 1. Crystals of 8, 11, and 14 were grown
from hexane at -5 °C. Crystals of 8, 11, and 14 were mounted
in thin-walled glass capillaries and sealed under argon. The
data sets of three crystals were collected on an Enraf CAD4
automated diffractometer. Mo KR radiation (λ ) 0.7107 Å) was
used for all structure. Each structure was solved by the
application of direct methods using the SHELX-96 program
and least-squares refinement using SHELX-97. All non-
hydrogen atoms in compounds 8, 11, and 14 were refined
anisotropically. All other hydrogen atoms were included in
calculated positions.
P r ep a r a tion of Ca r bor a n ylen e-1-d im eth yl(h yd r oxy)-
silyl-2-(1-p h en yl-b u t a n -3-on e)d im et h ylsila n e (11). To a
stirred toluene solution (10 mL) of 10 (0.18 g, 0.43 mmol) was
added H2O (0.02 g, 1.11 mmol) at room temperature. The
solution was stirred for 36 h at that temperature. The product
was isolated by chromatography using benzene/hexane (1:8)
as eluent in 92% yield: mp 139 °C; 1H NMR (CDCl3) δ 7.36-
7.08 (m, 5H, Ph), 2.55 (d, 2H, J HH ) 6.8 Hz, CH2), 2.35 (t, 1H,
J HH ) 6.8 Hz, CH), 2.16 (s, 1H, OH), 1.25 (s, 3H, CH3), 0.32
(s, 3H, SiCH3), 0.22 (s, 3H, SiCH3), 0.21 (s, 3H, SiCH3), 0.07
(s, 3H, SiCH3); 13C{1H} NMR (CDCl3) δ 207.06, 128.73, 128.64,
128.07, 127.87, 127.63, 127.04, 31.02, 29.44, 14.20, 2.42, 1.10,
0.59, -0.13; 29Si NMR (CDCl3) δ 19.22, -2.36; MS m/z 422
[M+]; IR (KBr pellet; cm-1) 3205 (m), 2968 (s), 2601 (s), 1683
(m), 1462 (m), 1384 (w), 1364 (w), 1261 (s), 1082 (m), 1052
(m), 1036 (m), 1017 (m), 910 (w), 864 (w), 855 (w), 804 (s). Anal.
Calcd for: C16H34B10O2Si2: C, 45.49; H, 8.05. Found: C, 45.18;
H, 7.86.
Ack n ow led gm en t. J .K. wishes to acknowledge the
financial support of the Korea Research Foundation
(H0181000) made in the program year of 1998.
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 8, 11, and 14. This
material is available free of charge via the Internet at
http://pubs.acs.org.
12 fr om th e r ea ction w ith r-Meth yl-tr a n s-cin n a m a l-
d eh yd e. Compound 12 was prepared by using the same
OM000527K