ALKENE OXIDATION CATALYZED BY TRANSITION-METAL SUBSTITUTED KEGGIN-TYPE HETEROPOLYANIONS

Alkene oxidations with various oxidants (tert-butyl hydroperoxide, iod osylbenzene and molecular oxygen in the presence of isobutyraldehyde ( IBA)) catalyzed by transition metal monosubstituted heteropolyanions, PW(11)MO(39)(n-) (PW(11)M; M = Co-II, Mn-II, Cu-II, Ti-IV, Ru-IV, V-V and Nb-V), have been studied. Orders of catalytic activity of PW(11)M are different for the oxidants studied. Radical chain mechanisms are p roposed for t-BuOOH and O-2/IBA. Preliminary coordination of the oxida nt to PW(11)M is not a necessary step of its homolytic activation. Epo xidation with PhIO requires its coordination to the catalyst and most likely includes the formation of active metal-ore species.