Cobalt complexes dioxygen adducts

A large number of type 1 dioxygen adducts are reported in the literature (25, 76, 80). The vast majority of metal complexes which take up dioxygen to form type I adducts contain cobalt(ll) as the metal ion. Ochiai (81) considered the hypothetical reactions ... 

We have seen, in the previous section (and section III.A), that cobalt (Salen) and its active derivatives normally form diamagnetic peroxo type I dioxygen adducts. However, a pyridine solution of Co(3-methoxy Salen) has been shown 137) to take up dioxygen with 1 1 (Co O2) stoichiometry it was found 137) that there was no significant IR absorption band, attributable to the 0—0 stretch, for the oxygenated complex, and this suggested that the dioxygen is symmetrically bonded in an unidentate manner,... 

An X-ray photoelectron spectroscopic study (132) of some cobalt(II) Schiff base complexes and their dioxygen adducts finds that the cobalt core electron binding energies in... 

This type of complex is derived from the mononuclear superoxo species via a further one-electron reduction of the dioxygen moiety. Cobalt is the only metal to form these complexes by reaction with dioxygen in the absence of a ligating porphyrin ring. Molybdenum and zirconium form peroxo-bridged complexes on reaction with hydrogen peroxide. In most cases the mononuclear dioxygen adducts of cobalt will react further to form the binuclear species unless specific steps are taken to prevent this. 

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