Kinetics of epoxidation of cyclooctene with H2O2 by α-Keggin [PTi2W10O38(O2)2]7- catalyst in acetonitrile

Ti(eta(2)-O-2)O-5 and adjacent W sites in alpha-Keggin [PTi2W10O38(O-2)(2)](7-) synergistically catalyze cyclooctene epoxidation and H2O2 dismutation in the monophastic [PTi2W10O38(O-2)(2)](7-)/H2O2/CH3CN system. The alkene coordination to the Ti(eta(2)-O-2)O-5 site precedes the epoxidation, and the decomposition of [PTi2W10O38(O-2)(2)](7-) by self-oxidation throughout the reactions is minor. From the kinetic results of the reactions it is inferred that the reaction pathway of the catalyst with H2O2 is altered by the alkene coordination to the Ti(eta(2)-O-2)O-5 site as an active site for the H2O2 dismutation, which modifies the electronic structure of surrounding sites, resulted in an active site for the epoxidation with an involvement of peroxo catalyst intermediates. (C) 1999 Elsevier Science B.V. All rights reserved.