Dioxygen Binding by Cobalt(II) Complexes of 8,8 -bis(aminomethyl)-2,2 -biquinoline

A new series of Co(II) complexes of the type CoLX2 , where L is a tetra-dentate ligand 8,8 -bis(aminomethyl)-2,2 -biquinoline and X= SCN–, BF4–, I– or NO3– , have been synthesized and characterized. The complexes have magnetic moments in the range typical of a low-spin d^7 Co(II) center. The interaction of these Co(II) complexes with dioxygen was studied by E.S.R. spectroscopy. A dicobalt(III) peroxo-bridged complex was formed in DMF solution, associated with the formation of an E.S.R.-silent solution compatible with the formation of low-spin d^6 Co(III) species. Similar behavior was also observed for the interaction of these Co(II) complexes with dioxygen in the presence of ancillary ligands such as pyridine and 2-methylimidazole. The dioxygen complexes proved successful as oxygen carrier oxidation catalysts for tripehnylphosphine and 2,6-bis(t-butyl)phenol.