Efficient and reusable catalysis of benzylic C–H oxidation over layered [Co5(OH)6]4+ derivatives

Abstract

Aerobic oxidation of benzylic C(sp³)–H bonds in a green and heterogeneous manner is a major target in organic catalysis. Herein, we report the synthesis of 3D coordination polymers containing [Co₅(OH)₆]⁴⁺ layers, affording reusable and efficient oxidation of ethylbenezene and tetralin by using O₂ as the oxidant. Moreover, the cleavage of Co^II–carboxylate bonding renders atomically thin cobaltate nanosheets and enhanced catalytic performance. This is one of the top catalytic performances for Co^II-catalyzed benzylic C(sp³)–H oxidation (∼0.02 mol% Co and 76% conversion for nanosheets), ascribed to the exposed, accessible and coordinatively unsaturated Co^II species.