Chemistry Reference
In-Depth Information
n
-hexane
1
2
t
2
t
2
t
2
Li(CH
2
PPh
2
)(tmeda) + 2Bu CO
[Li(OCBu CH
2
PPh
2
)
2
Li(OCBu )]
2
.
158
Similarly, acetone adds to the Ga-H bond in dichlorogallane under mild conditions
to give gallium dichloride monoisopropoxide
423
HGaCl
2
C
CH
3
2
CO ! GaCl
2
OCH
CH
3
2
2
.
159
Ketones (hexafluoroacetone) insert across a Si-H bond to form the corresponding
silicon alkoxide derivative:
424
,
425
Me
3
SiH C
CF
3
2
CO ! Me
3
SiOCH
CF
3
2
2
.
160
2.10.7
By Exchange Reactions (J-7)
Exchange reactions between two different metal chlorides and alkoxides have been
employed for the synthesis of a wide variety of homo- and heteroleptic metal alkox-
ides. For example, Bradley and Hill
426
observed that a mixture of excess titanium
tetrachloride and silicon dichloride diethoxide at 0
Ž
C deposited a crystalline product
which was characterized as titanium trichloride monoethoxide:
TiCl
4
C SiCl
2
OEt
2
! TiCl
3
OEt
#CSiCl
3
OEt
2
.
161
Similarly titanium trichloride monoethoxide was obtained by reactions of titanium
tetrachloride with silicon monochloride triethoxide or silicon tetraethoxide (Eqs 2.162
and 2.163).
TiCl
4
C SiCl
OEt
3
! TiCl
3
OEt
C SiCl
2
OEt
2
2
.
162
TiCl
4
C Si
OEt
4
! TiCl
3
OEt
C SiCl
OEt
3
2
.
163
Following the use of exchange reactions between TiCl
4
and Si
OEt
4
/
SiCl
OEt
3
,
Marks and co-workers
427
have shown that uranium hexamethoxide can be prepared in
the direct reaction between UF
6
and an excess of MeSi
OMe
3
(Eq. 2.164).
CH
2
Cl
2
!
76
°
C
UF
6
C 2MeSi
OMe
3
U
OMe
6
C 2MeSiF
3
2
.
164
Jacob
428
has described a variation of this reaction by using Si
OMe
3
4
for the
synthesis of hexamethoxides of uranium, molybdenum and rhenium (Eq. 2.165).
MF
6
C 6Si
OMe
4
! M
OMe
6
C 6SiF
OMe
3
2
.
165
where M D U, Mo, Re.
For M D Mo, the reaction proceeds to completion if the product SiF
OMe
3
in
Eq. (2.165) is removed during the reaction by pumping.
Analogous reaction with WF
6
affords WF
OMe
5
, which on reaction with NaOMe
yields W
OMe
6
.
428
