Two Copper-Containing Polyoxometalate-Based Metal–Organic Complexes as Heterogeneous Catalysts for the C–H Bond Oxidation of Benzylic Compounds and Olefin Epoxidation

Abstract

Using a one-pot assembly method, two novel copper-containing Keggin-type polyoxometalates (POMs)-based metal–organic complexes, that is, [CuII2(pbba)2NO3–(H2O)2(PW12O40)]·3H2O [PW12-Cu-pbba, H2pbba = 1,1′-(1,4-phenylene-bis(methylene))-bis(pyridine-3-carboxylic acid)] and [CuII2(pbba)2(H2O)2(GeW12O40)]·3H2O (GeW12-Cu-pbba), were successfully synthesized. These two complexes are isostructural, differing only in their POM components. They are applicable as heterogeneous catalysts for the C–H bond oxidation of benzylic compounds and olefin epoxidation under mild conditions, with oxygen as the oxidant and isobutyraldehyde as the coreductant. The catalytic activity of PW12-Cu-pbba was superior to that of GeW12-Cu-pbba. Under the optimal conditions, PW12-Cu-pbba catalyzed the oxidation of indane into 1-indanone with an 81% yield and >99% selectivity within 48 h. As heterogeneous catalysts, both complexes demonstrated excellent recoverability and high stability and could be stably reused five times without significant activity loss.