CHARACTERIZATION OF A MU-ETA(2)ETA(2)-PEROXO DINUCLEAR COBALT(II) COMPLEX

A novel dicobalt(II) mu-peroxo complex (3) is formed by the reaction o f a dicobalt(II) bis(mu-hydroxo) complex, [Co(HB(3,5-iPr(2)pz)(3))](2) (OH)(2) (2), with a stoichiometric amount of H2O2. Unusual and charact eristic spectroscopic properties [(1) existence of two O-2(2-) to meta l charge transfer absorption bands; (2) low v(O-O) vibration in the re sonance Raman spectrum; (3) antiferromagnetic coupling between the two Co(II) ions] suggest that the peroxo ligand coordinates in the planar mu-eta(2):eta(2) binding mode as found in the oxyhemocyanin and the d icopper(II) peroxo model complexes. Warming of a pentane solution of 3 induces aliphatic C-H bond activation concomitant with O-O bond cleav age to yield the novel mu-alkoxo-mu-hydroxo complex 4, -5-iPrpz)(3,5-i Pr(2)-pz)(2)][HB(3,5-iPr(2)pz)(3)], and the bis(mu-hydroxo) complex 2.