Chemistry Reference
In-Depth Information
Reactions similar to those represented by Eq. (2.264) have been observed for primary
and secondary alkoxides of beryllium,
903
yttrium and lanthanides,
148
,
156
,
904
,
905
titanium
and zirconium,
647
,
670
,
906 - 911
vanadium,
912
niobium,
913
tantalum,
914
uranium,
915
iron,
916
aluminium,
917
gallium,
918
silicon,
919
germanium,
920
as illustrated by the following
equations in a few typical cases:
Be
OEt
2
C 2CH
3
COX ! BeX
2
.
2CH
3
COOEt
2
.
265
Zr
OPr
i
4
.
Pr
i
OH C CH
3
COX ! ZrCl
OPr
i
3
.
Pr
i
OH C CH
3
COOPr
i
2
.
266
Zr
OPr
i
4
C
x
CH
3
COX
! Zr
OPr
i
4
x
X
x
.
y
CH
3
COOPr
i
C
x
y
CH
3
COOPr
i
2
.
267
where
y
D 0, 0.5, 1, 2 respectively when
x
D 1, 2, 3, 4.
Al
OEt
3
C
x
CH
3
COX ! Al
OEt
3
x
X
x
.
y
CH
3
COOEt C
x
y
CH
3
COOEt
2
.
268
where
y
D 0, 0.5, 1.5 respectively when
x
D 1, 2, 3.
HSi
OPr
i
3
C
x
CH
3
COCl ! HSi
OPr
i
3
x
Cl
x
C
x
CH
3
COOPr
i
2
.
269
All the above reactions have been found to be quite facile and have been mostly
carried out with metal isopropoxides and also with ethoxides in some cases. The 1:1
molar reaction of the alcoholate, Zr
OPr
i
4
.
Pr
i
OH with CH
3
COCl showed that the
zirconium isopropoxide moiety is more reactive than the coordinated isopropyl alcohol
molecule.
In an early paper,
913
the formation of products of lower chloride:zirconium ratios, as
compared to the moles of acetyl chloride employed with zirconium tetra-
tert
-butoxide,
was ascribed to steric effects. However, in a careful re-examination, the reactions
between metal
tert
-butoxides and acetyl halides have been found
923 - 926
to follow an
entirely different course. For example, the reaction between zirconium tertiary butoxide
and acetyl chloride was slow, and complete replacement of even one mole of tertiary
butoxo group was not achieved; the equimolar reaction product had the average compo-
sition, ZrCl
0
.
7
OBu
t
3
.
3
. On the basis of further reaction of zirconium chloride tertiary
butoxide with acetyl chloride it appeared that a side reaction occurred and instead of
higher chloride alkoxides, mixed-alkoxide acetates were formed:
slow
!ZrCl
OBu
t
3
C CH
3
CO
2
Bu
t
Zr
OBu
t
4
C CH
3
COCl
2
.
270
ZrCl
OBu
t
3
C
x
CH
3
COCl !ZrCl
1C
x
OBu
t
3
x
C
x
CH
3
CO
2
Bu
t
2
.
271
ZrCl
OBu
t
3
C
x
CH
3
COCl !ZrCl
OCOCH
3
x
OBu
t
3
x
C
x
Bu
t
Cl
2
.
272
The above reaction in 1:6 molar ratio afforded zirconium monochloride triacetate
ZrCl
OAc
3
. The formation of acetate derivatives of the tertiary butoxide was con-
firmed by the reaction of zirconium tetrachloride with excess of tertiary butylacetate,
