The Si-Ge Bond
Organometallics, Vol. 18, No. 15, 1999 2857
appeared at 1.1 ppm. At this point bubbling of hydrogen
chloride was discontinued, and 2 mL of acetone was added to
deactivate the AlCl3 catalyst. Removal of the solvents, followed
by the distillation (bp 88-90 °C/48 mmHg) of the residue, gave
0.9 g (3.98 mmol, 53.5% yield) of ClGeMe2CH2SiMe3.
Syn th esis of ClSiMe2CH2GeMe3. The Grignard reagent
Me3GeCH2MgCl was synthesized from 2.51 g (15.0 mmol) of
Me3GeCH2Cl and 0.36 g (0.015 g-atom) of Mg in 30 mL of dry
diethyl ether. The Grignard reagent was added dropwise to
1.93 g (15.0 mmol) of Me2SiCl2 in 20 mL of diethyl ether at 0
°C. The reaction mixture was stirred at this temperature for
about 3 h and then brought to room temperature slowly and
stirred for 18 h. Diethyl ether was distilled, and salts were
precipitated with 50 mL of hexane. After filtration and removal
of solvents, the colorless liquid product, ClSiMe2CH2GeMe3,
was distilled at 86-88 °C/48 mmHg. Yield: 0.5 g (2.21 mmol,
14.7%).
AlCl3 Tr ea tm en t of ClSiMe2GeMe3. A 100 mL sidearm
flask was fitted with a magnetic stirring bar and a Claisen
adapter with a nitrogen inlet at the top. To a solution of 4 g
(18.8 mmol) of 1 in 30 mL of benzene was added 1.14 g (8.5
mmol) of anhydrous aluminum chloride. The mixture was
stirred at room temperature for 48 h and monitored by 29Si
NMR for that period. The disappearance of the 29Si NMR
signal at 28 ppm indicated the reaction was complete. The
reaction mixture was then flash-distilled under vacuum to
separate the product from the aluminum chloride catalyst.
Fractional distillation of this catalyst-free distillate gave 2 g
(9.4 mmol, 50%) of the isomer ClGeMe2SiMe3.
AlCl3 Tr ea tm en t of ClGeMe2SiMe3. The procedure was
the same as above except that 1 g (4.7 mmol) of compound 3
was allowed to react with 0.28 g (2.1 mmol) of anhydrous
aluminum chloride. No rearrangement of this compound
occurred, and instead fragmentation of the compound was
observed. The main fragmentation involved cleavage of the Si-
Ge bond and produced trimethylchlorosilane, as evidenced by
NMR spectral data.
AlCl3 Tr ea tm en t of ClCH2SiMe2GeMe3. A 100 mL side-
arm flask was fitted in the same fashion as above. To the flask
was added a solution of 3 g (13.3 mmol) of 2 in 35 mL of
benzene and then 0.8 g (5.9 mmol) of anhydrous aluminum
chloride. The mixture was stirred at room temperature for 10
h and monitored by 29Si NMR; ClCH2SiMe2GeMe3 (29Si NMR
(δC6D6): -7.2 ppm) rearranged smoothly to produce 2.09 g (9.3
mmol, 70%) of the isomer ClSiMe2CH2GeMe3 (4) (29Si NMR
(δC6D6): 31 ppm).
Rea ction of MeLi w ith P h 3SiGeMe3. To 0.25 g (0.66
mmol) of Ph3SiGeMe3 in 5 mL of THF in a 50 mL round-
bottomed Schlenk flask was added 0.45 mL of MeLi (1.4 M
solution in ether) at room temperature and stirred for 1 h. The
color of the solution turned light brown, and 0.18 g of Ph3-
GeCl (0.66 mmol) dissolved in 5 mL of THF was added. The
color of the solution disappeared immediately. The solvent was
removed, and the residual white solid was dissolved in 10 mL
of hexane and filtered. GC/MS analysis of the filtrate showed
it to be a mixture of Ph3SiMe and Ph3GeGeMe3. After recrys-
tallization from hexane 0.22 g of Ph3GeGeMe3 (0.52 mmol,
78%) was obtained as a first crop. The mother liquor was
decanted into another flask and concentrated to give 0.14 g
(0.51 mmol, 77%) of Ph3SiMe. Both materials were identified
by spectroscopic analysis and comparison with authentic
materials.
Syn th esis of 1,1′-GeMe2SiMe2(η5-C5H4)2F e. To 2.8 g (15.0
mmol) of ferrocene, dissolved in 150 mL of hexanes in a 250
mL Schlenk flask, was added 5.5 mL (37 mmol) of TMEDA
followed by 23 mL (37 mmol) of an n-BuLi solution (1.6 M) in
hexane. The mixture was stirred overnight at room temper-
ature. During this time an orange precipitate formed and the
solution was red in color. The solution was transferred via
cannula to another flask, and the orange precipitate was
washed with hexanes three times. To the precipitate was
added 50 mL of hexanes, the flask was cooled to -78 °C, and
then 3.5 g (15.0 mmol) of ClSiMe2GeMe2Cl (dissolved in 20
mL of hexanes) was added dropwise and the reaction mixture
was brought to room temperature slowly and stirred overnight.
The solution was filtered through Celite and, after removing
the solvent, yielded a yellow solid. The yellow solid was
recrystallized from hexanes to yield 9, 2.1 g (6.1 mmol, 57%),
mp 128-129 °C.
Rea ction of MeLi w ith 1,1′-GeMe2SiMe2(η5-C5H4)2F e. To
0.100 g (0.29 mmol) of 1,1′-GeMe2SiMe2(η5-C5H4)2Fe in 10 mL
of THF in a 100 mL Schlenk flask was added 0.20 mL of MeLi
at room temperature. Immediately, the color of the solution
turned dark orange, and the solution was stirred for 1 h. A
solution of Ph3GeCl (0.098 g, 0.29 mmol dissolved in 10 mL of
THF) was added to the dark orange-colored solution. The
solution was stirred for 30 min, and then the THF was
removed. An orange waxy material was extracted in 20 mL of
hexane. The solution was filtered, concentrated to 5 mL, and
chromatographed on a 2 × 25 cm silica gel column. The orange
band was extracted with hexane. Hexane was removed, and
0.120 g (0.19 mmol, 66%) of (η5-C5H4GeMe2GePh3)Fe(η5-C5H4-
SiMe3) was obtained as an orange solid (mp 73-75 °C ).
The reaction of a catalytic amount of MeLi with [1,1′]-
tetramethylsilylgermylferrocenophane resulted in the forma-
tion of a small amount of ferrocenylene polymer (<5%).
Tr ea tm en t of F p SiMe2GeMe2F p w ith 1 equ iv of LDA.
To a 50 mL THF solution of FpSiMe2GeMe2Fp (0.60 g, 1.16
mmol) was added 2.0 mL of a 0.56 M solution of freshly
prepared LDA in THF at -25 °C. There was an immediate
color change from yellow to red-orange, and after the solution
had been stirred for 1 h, IR monitoring showed the formation
of the anion by the appearance of ν(CO) bands at 1868.1,
1812.3, 1779.5, and 1753.9 cm-1. This solution was treated
with Me3SnCl (0.230 g, 1.15 mmol) and slowly brought to room
temperature. The solvent was removed, and the resulting
reddish-brown waxy material was extracted with 30 mL of
hexane and filtered. The solution was concentrated to 5 mL
and placed on a 2.5 × 10 cm alumina column. The resulting
yellow band was eluted with hexane. Removal of the solvent
yielded a mixture of starting material (40%), (η5-FpGeMe2-
SiMe2C5H4)Fe(CO)2SnMe3 (50%), and (η5-FpSiMe2GeMe2C5-
H4)Fe(CO)2SnMe3 (10%). The migrated product was contami-
nated with a small amount of starting material even after
repeated crystallization (mp 132-134 °C).
Tr ea tm en t of F p SiMe2GeMe2F p w ith 2 equ iv of LDA.
To a THF solution (50 mL) of FpSiMe2GeMe2Fp (0.40 g, 0.77
mmol) in a 100 mL Schlenk flask was added 4.00 mL (1.80
mmol) of a LDA solution at -25 °C. The solution turned deep
orange, and the solution was stirred for 2 h. IR monitoring of
the reaction at this time indicated the presence of ν(CO) bands
at 2005.6, 1989.5, 1944.2, 1916.0 1867.1, 1809.8, 1773.5, and
1751.2 cm-1. A solution of Me3SnCl (0.310 g) in 10 mL of THF
was added at -25 °C, and after 1 h IR analysis showed only
two bands at 1978.7 and 1927.6 cm-1. The solvent was
removed, and the resulting brown waxy material was extracted
with a 90:10 hexane/methylene chloride mixture. This solution
was placed on a 2.5 × 10 cm alumina chromatography column.
The resulting yellow band was eluted with a 90:10 hexane/
methylene chloride mixture. Removal of the solvent and
recrystallization from hexane yielded 0.38 g (0.45 mmol, 58%)
of yellow (η5-{Me3SnFe(CO)2(η5-C5H4SiMe2GeMe2C5H4)}Fe(CO)2-
SnMe3) (mp 135-137 °C).
Resu lts a n d Discu ssion
Alu m in u m Ch lor id e In ter a ction s w ith Ha lo- a n d
Ha lom eth ylsilyl(ger m yl)ger m a n e(sila n e). The reac-
tions of the silicon-germanium-bonded compounds 1,
2, 3, and 5 with AlCl3 led to products that involved
molecular rearrangements (1 f 3, 2 f 4, and 5 f 6) or
Sharma, Sneh
