Vanadium complexes alkyl transfer reactions

The rate of polymerization of polar monomers, for example, maleic anhydride, acrylonitrile, or methyl methacrylate, can be enhanced by coraplexing them with a metal halide (zinc or vanadium chloride) or an organoaluminum halide (ethyl aluminum sesqui-chloride). These complexed monomers participate in a one-electron transfer reaction with either an uncomplexed monomer or another electron-donor monomer, for example, olefin, diene, or styrene, and thus form alternating copolymers (11) with free-radical initiators. An alternating styrene/acrylonitrile copolymer (12) has been prepared by free-radical initiation of equimolar mixtures of the monomers in the presence of nitrile-coraplexing agents such as aluminum alkyls. 

Although these reactions obviously involve intramolecular oxygen transfer within a titanium(IV) tartrate-ally lie alcohol-alkyl hydroperoxide complex, analogous to the vanadium-catalyzed epoxidations discussed above, the exact nature of the catalytic species and the mechanism of enantioselection remain controversial [39, 40],... 

---