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

This work presents two mixed-valent mu(3)-oxo-bridged trinuclear [(Co2+)(2)Co3+] complexes 1 and 2 and a mu(4)-oxo-bridged tetranuclear [Co-4(2+)] complex 3. Crystal structures of 1 and 2 showed the presence of triangular complexes having two Co2+ and one Co3+ centers bridged by a mu(3)-oxo group. In contrast, complex 3 exhibited a tetrahedrally arranged mu(4)-oxo-bridged [Co-4(2+)] core. A significant feature is the stabilization of unusual mu-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 H2O2-mediated oxidation of assorted benzyl alcohols.

Automated summary

This work presents three cobalt complexes with different types of oxygen bridges, and discovers the novel feature of stabilizing these complexes with all nitrogen donor ligands. X-ray photoelectron spectroscopy further confirms the multiple oxidation states of cobalt ions in these complexes. These complexes also show catalytic activity in the oxidation reactions.