Mechanisms of oxidant activation in alkene epoxidation catalyzed by monosubstituted heteropolytungstates

作者：Kholdeeva OA^*; Grigorev VK; Maksimov GM; Zamaraev KI

来源：Kinetics and Catalysis, 1997, 38(4): 507-512.

The catalytic activity of monosubstituted heteropolytungstates PW11MO39n- (PW11M; M = Co(II), Mn(II) Cu(II), Ti(IV), Ru(IV), V(V), Nb(V)) was studied in alkene oxidations by various oxidants (tert-butyl hydroperoxide, iodosobenzene, and dioxygen) in the presence of isobutyraldehyde (IBA). Activity series of PW11M were found to be different for the oxidants studied. The composition of reaction products depends on the alkene structure and the nature of oxygen donor. The radical-chain mechanism was proven for the reactions of alkenes with t-BuOOH and O-2/IBA where alkylperoxy and acylperoxy radicals are active epoxidants. Prior coordination of an oxidant to heteropoly anion is not a necessary stage for the oxidant homolytic activation. Alkene epoxidation by iodosobenzene occurs via oxidant coordination to the catalyst and has a heterolytic mechanism, which involves the formation of metal oxy species.

• 出版日期1997-8