Type I Dioxygen Complexes

Further to section III(C), we shall see that type I dioxygen complexes can be formed in solution via intermediates of a type 11(F) structure. Consequently, sections IV( ) and IV(F) will tend to overlap in places. The dioxygen adducts of some new synthetic metal porphyrins belong to the 11(F) classification. However, a discussion of the dioxygen adducts of naturally occurring and synthetic metal porphyrins is postponed until section V. 

Previous reviews on dioxygen complexes (i, 19,25, 76-79) cover the workup to and through 1972, and will not be totally incorporated within this present review, in the sense that we intend to provide a clarification of the concepts and principles appertaining to reversible oxygenation and not an exhaustive catalogue of data, for which we cite the original papers and reviews. We cover the literature through 1975. 

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  

These conclusions are supported by another ESR study (Jd) made on some oxygenated cobaltoximes(II), which showed that the dioxygen species finally formed is best characterized as a peroxo-bridged complex these being reversibly formed binuclear complexes. 

It has been noted (84) that U-dioxygen (type 1) complexes formed in solution often contain a u-hydroxo bridge, in addition to the /i-dioxygen bridge, provided that each cobalt atom has a vacant coordination site. Fig. 4 illustrates the dibridged M-(02, OH)—M moitey 

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