2 Homometallic Alkoxides

Homometallic Alkoxides 133
which yielded zirconium tetraacetate containing a small proportion of chloride as
impurity [ZrCl0.2⊲OAc⊳3.8].
Contrary to the facile straightforward reactions of ethoxides and isopropoxides of
different metals according to Eq. (2.268), an entirely different course of reaction,
resulting in the final formation of metal acetate, can be further illustrated by the reaction
of aluminium tertiary butoxide with acetyl chloride. In this case, the first stage of
the reaction is fast, but the aluminium monochloride di-tert-butoxide formed initially
reacts 926 with tertiary butylacetate also formed during the reaction, to produce the
corresponding mixed alkoxide-acetate:
Al⊲OBu t ⊳3 C xCH3COCl ! Al⊲OBu t ⊳3 x Clx C xCH3COOBu t
⊲2.273⊳
AlClx⊲OBu t ⊳3 x C yCH3COOBu t ! Al⊲OBu t ⊳3 x ⊲OCOCH3⊳yClx y C yBu t Cl
⊲2.274⊳
where x D 1–3; y D 0or< x.
This assumption was confirmed by treating aluminium trichloride with tertiary butylacetate,
whereby aluminium triacetate was finally obtained:
AlCl3 C 3CH3COOBu t ! Al⊲OCOCH3⊳3 C 3Bu t Cl ⊲2.275⊳
4.11.4 Reactions with Metal Halides
The reactions between titanium tetra-alkoxides and titanium tetrachloride (excess) at
low temperatures lead to the deposition of less soluble titanium trichloride mono-
alkoxides: 909,927
Ti⊲OR⊳4 C 3TiCl4
(excess)
! 4TiCl3⊲OR⊳ ⊲2.276⊳
In the case of zirconium, crystalline chloride-isopropoxide complexes 913 have been
obtained according to the reactions illustrated by Eqs (2.277) and (2.278):
Zr⊲OPr i ⊳4.Pr i OH C ZrCl4.2MeCO2Pr i
! ZrCl2⊲OPr i ⊳2.Pr i OH C ZrCl2⊲OPr i ⊳2.MeCO2Pr i C MeCO2Pr i ⊲2.277⊳
Zr⊲OPr i ⊳4Pr i OH C ZrCl2⊲OPr i ⊳2.Pr i OH ! 2ZrCl⊲OPr i ⊳3.Pr i OH ⊲2.278⊳
These reactions are not confined to metal chloride/metal alkoxide systems, but are
also applicable to organometal chloride/organometal alkoxide combinations as demonstrated
by Eqs (2.279)–(2.282):
xMeTiCl3 C yMeTi⊲OR⊳3
CH2Cl2
! ⊲x C y⊳MeTiClx ⊲OR⊳y 928
⊲2.279⊳
where R D Et, Pr i ; x D 2, y D 1orx D 1, y D 2; the dichloro derivatives are less
stable.
2RSnCl3 C RSn⊲OPr i ⊳3
RSnCl3 C 2RSn⊲OPr i ⊳3
R2SnCl2 C R2Sn⊲OMe⊳3
! 3RSnCl2⊲OPr i ⊳ 210
! 3RSnCl⊲OPr i ⊳2 210
! 2R2Sn⊲OMe⊳Cl 210
⊲2.280⊳
⊲2.281⊳
⊲2.282⊳