Chemistry Reference
In-Depth Information
metal alkoxides and hydrogen halides were essentially the same as those obtained in
the reactions involving the metal chloride and an alcohol:
benzene
! M
OR
x
y
X
y
C
y
ROH
M
OR
x
C
y
HX
2
.
254
Ti
OR
4
C 2HX ! Ti
OR
2
X
2
.
ROH C ROH
2
.
255
where R D Et, Pr
i
;XD Cl, Br.
2Zr
OR
4
C 5HX ! Zr
OR
X
3
.
2ROH C Zr
OR
2
X
2
.
2ROH C ROH
2
.
256
Th
OR
4
C 4HX ! ThX
4
.
4ROH
2
.
257
where R D Et, Pr
n
,Pr
i
;XD Cl, Br.
Gilman and co-workers
898
have also shown that interaction of uranium pentaethoxide
and hydrogen chloride in appropriate molar ratios of reactants in ether afforded the
products: UCl
OEt
4
,UCl
2
OEt
3
,andUCl
3
OEt
2
.
In contrast to the non-reactivity of Si
OR
4
towards hydrogen halides, germanium
295
and tin tetra-alkoxides
899
show high reactivity on interaction with HCl as shown by
Eqs (2.258) and (2.259):
benzene
! GeCl
4
C 4ROH
Ge
OR
4
C 4HCl
2
.
258
2Sn
OR
4
C 7HCl ! SnCl
3
OR
.
ROH C SnCl
4
.
2ROH C 4ROH
2
.
259
An equimolar reaction of As
OMe
5
and HCl or HF gives AsX
OMe
4
(X D F,
Cl);
900
the fluoro derivative was stable
in vacuo
below 30
Ž
C whereas the chloro
analogue appeared to be unstable and decomposed
AsCl
OMe
4
! AsO
OMe
3
C
MeCl
to give arsenyl trimethoxide and methyl chloride.
In contrast to the partial reactions illustrated by Eq. (2.254), complete substitution
has been shown to occur to give metal halides that are known to form only alcohol
adducts when treated with alcohols:
Th
OPr
i
4
C 4HCl
benzene
! ThCl
4
.
4Pr
i
OH
2
.
260
benzene
! LnCl
3
.
3Pr
i
OH
Ln
OPr
i
3
C 3HCl
2
.
261
where Ln D a lanthanide.
102
Fe
OPr
i
3
C 3HCl ! FeCl
3
.
2Pr
i
OH C Pr
i
OH
210
2
.
262
Te
OEt
4
C 4HCl ! TeCl
4
.
3EtOH C EtOH
901
2
.
263
4.11.3 Reactions with Acyl Halides
The reactions of metal alkoxides with acyl halides may be illustrated by Eq. (2.264):
benzene
! M
OR
x
y
X
y
.
z
CH
3
COOR C
y
z
CH
3
COOR
2
.
264
M
OR
x
C
y
CH
3
COX
where R D Et, Pr
i
;XD Cl, Br;
y
D 1
,
2
,
3
,
4
...
x
;
z
D 0, 0.5, 1.
This type of facile reactivity was first observed in 1936 by Jennings
et al
.
902
who
synthesized titanium monochloride triethoxide and dichloride diethoxide by the reac-
tions of titanium tetraethoxide and acetyl chloride in the appropriate molar ratios.
