Polyoxometalate-supported Transition Metal Complexes for Oxidative Cross-Coupling of Amines and Alcohols

Abstract

Three new hybrid polyoxometalates (POMs) based on transition metals like copper metal with γ-[Mo8O26]4- polyoxometalates, [Cu(DMF)4(Mo8O26)⸱2C3H8NO]⸱1.8 DMF (1), cobalt and nickel metals with hexamolybdate [Co(DMSO)6][Mo6O19] (2), [Ni(DMSO)6][Mo6O19] (3) have been developed. These materials have been characterised by both analytical and spectroscopic techniques (IR, TGA, and CHNO elemental analysis), and structural elucidation has been done using single crystal X-ray diffraction studies. Among these hybrid POMs, the octamolybdate with copper has been used for catalytic production of benzimidazoles. The incorporation of the [Cu(DMF)4] between two octamolybdates results in transformation of POM into useful catalyst, which effectively catalyses the oxidative cross-coupling of anilines, benzyl alcohol, and sodium azide to produce benzimidazole. This catalytic reaction takes place in the presence of tert-Butyl Hydroperoxide (TBHP) at moderate temperature. Benzimidazole and its derivatives are highly preferred due to their wide-ranging biological activities and clinical applications. These compounds are exceptionally effective in terms of both their selectivity ratio and inhibitory activity. The catalytic reaction presented here, is a one-pot component procedure that includes a series of reactions like C-H functionalization, condensation, ortho selective amination, and cyclization.