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.