A New Cobalt(III)/[Mo6O19]2− Heterogeneous Catalyst for Promoting the Oxidative Coupling of Amines to Imines

Abstract

Currently, the efficient preparation of imines is still a great challenge under mild conditions. In this article, by incorporating 2-acetylpyridine thiosemicarbazone (HL), Co(NO3)2·6H2O and Na2MoO4·2H2O, a new compound [Co(L)2]2[Mo6O19] (1) was prepared and characterized by elemental analysis (EA), infrared (IR) spectra, ultraviolet–visible (UV–Vis) spectra, powder X-ray diffractometry (PXRD) spectra, X-ray photoelectron spectroscopy (XPS) and X-ray single-crystal diffraction. 1 could be used as a heterogeneous catalyst for oxidative coupling of amines in a comparatively mild condition. Furthermore, 1 exhibited remarkable catalytic performance for oxidation coupling of amines to imines with high yield in the presence of tert-butyl hydroperoxide (TBHP) (up to 92%). Kinetic measurements of the oxidation of benzylamine suggest that the rate law is r = k′[BnNH2][TBHP] (k′ = k[cat] = 0.2338 L mol−1 h−1). Additionally, 1 can be recycled at least three times without a distinct loss of activity. A new compound [Co(L)2]2[Mo6O19] (1) (HL = 2-acetylpyridine thiosemicarbazone) has been synthesized and characterized. Furthermore, 1 can efficiently catalyze the oxidative coupling of amines to imines with high activity and exhibited good recyclability and high stability.