ABSTRACT
Monomeric vanadate reacts rapidly and reversibly with alcohols and phenols, with reaction occurring within a few milliseconds at room temperature. The products correspond to alkoxovanadate derivatives, the mono-and diesters. The criterion is that the vanadate is protonated so that an OH can be replaced by OR or OAr with release of water. The reactions are quite weak when compared to many other ligands, formation constants (V + L VL) being about 0.2 M
under neutral conditions for formation of ethylvanadate and about 5 times as large for phenylvanadate. The subsequent incorporation of a second ligand to form the diester proceeds with similar formation constants. Under strongly forcing conditions where no water is present, the triester can be formed from the alcohol, but it rapidly hydrolyzes in the presence of water. In nonaqueous solution, there is a marked tendency for the triesters to form dimers [1], with structures similar to those found for diol complexes (Section 4.1.1). The dimerization reaction does, however, seem to be sensitive to the steric bulk of the ligand, and triesters prepared from bulky alcohols apparently do not form dimers [2]. Interestingly enough, the oxovanadium(V) triester formed from isopropanol serves as a versatile material for generating vanadium pentoxide-based nanorods, nanowires, and nanotubes (Chapter 12).
