Heterometallic alkoxides with alcohols

A modification of this route is a simultaneous reaction of two metals with alcohol that can be considered as the in situ reaction of the alkoxides formed. Thus the interaction of Mg and A1 with ethanol (leading to the formation of the perfectly soluble MgAl2(OEt)8) occurs very rapidly and does not need activation, in contrast with the reactions of individual metals with alcohol, leading to polymeric Mg(OEt)2 andAl(OEt)3 [1101, 887] (see Section 2.1). The preparation of the heterometallic derivatives has been achieved even via anodic oxidation of one metal in solution of the other (the complex solutions obtained have been used for the deposition of films in sol-gel technique) [1777]. 

The intensive development of the chemistry of homo- and heterometallic alkoxides of copper started more than 10 years ago in connection with the prospects of their application in the preparation of materials and initially in high temperature superconductors. In the search for the appropriate precursors in sol-gel and MOCVD techniques, attention was focused on the alkoxides of copper (I) and the fluorinated alkoxides of copper (II) — oligomeric derivatives soluble in non-polar solvents and existing not only in condensed but also in the gas phase. The derivatives of copper (II) and aliphatic alcohols, even rather branched or functional ones (such as alkoxyalkoxides) turned out to be polymeric substances uninteresting for further application. 

Heterometallic alkoxides of calcium, strontium, and barium with transition or posttransition metals have been formed by reactions with the preformed alkoxides (e.g., Table 8, Equations (8a) and (8b)). A variation on this approach generates the Group 2 alkoxides in situ by reaction of the metal with an alcohol and/or another alkoxide (e.g.. Table 8, Equations (9a) and (9b)). " " ... 

Oxo-alkoxides are partially condensed species and represent a new class of sol-gel precursors. These species are oligomeric and can be either homometallic or heterometallic. In many cases the oxo bridges produced in these compounds are multiply bridging, in order to achieve the most favored coordination number of six for metal atoms in alkoxide species. Isolation of compounds with similar multiply bridging oxygen atoms has been observed by the reaction of metals with the appropriate phenol or alcohol, with, in some cases, reaction with solvent molecules producing compounds quite different from the simple binary alkoxides expected.72 Besides isolation of intermediates, it is also possible to monitor the reactions by NMR and mass spectrometry 73... 

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