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.