Oxo‐bridged Tri‐ and Tetra‐nuclear Cobalt Complexes Supported with Amide‐Based Nitrogen Donor Ligands

Abstract

This work presents two mixed-valent μ 3 -oxo-bridged trinuclear [(Co 2 + ) 2 Co 3 + ] complexes 1 and 2 and a μ 4 -oxo-bridged tetranuclear [Co 2 + 4 ] complex 3. Crystal structures of 1 and 2 showed the presence of triangular complexes having two Co 2 + and one Co 3 + centers bridged by a μ 3 -oxo group. In contrast, complex 3 exhibited a tetrahedrally arranged μ 4 -oxo-bridged [Co 2 + 4 ] core. A significant feature is the stabilization of unusual μ-oxo-bridged complexes exclusively supported with all nitrogen donor ligands. The X-ray photoelectron spectroscopy confirmed the multiple oxidation states of cobalt ions in these complexes. Such oxo-bridged cobalt complexes were investigated for their catalytic activity towards H 2 O 2 -mediated oxidation of assorted benzyl alcohols.