Superoxo complexes binuclear

The structure of the active component, manganese pyrophosphate, has been reported in the literature (24). It is layer like with planes of octahedrally coordinated Hn ions being separated by planes of pyrophosphate anions (P20y ). Examination of models of this compound gave calculated Hn-Hn thru space distances of 3.26 and 3.45 angstroms, a metal-metal distance close to that found for binuclear dibridged peroxo- and superoxo- complexes of cobalt ( ). 

Although there are no binuclear superoxo complexes formed simply by the interaction of a metal complex and dioxygen, they are worthy of discussion here if only to complement mononuclear... 

Sulfur ligands, 633-655 coordination ability, 516 Sulfur monoxide metal complexes instability, 636 Superoxide dismutase, 773 copper complexes, 772 Superoxo complexes, 315-330 binuclear, 323, 325 reactions, 330 bridged... 

Since all these amino-bridged binuclear complexes can be inter-converted 135,136) starting with the green superoxo complex... 

The Co(II)salpr complex does not form a binuclear C0-O2-C0 complex with molecular oxygen (60). Despite this, hydrogen abstraction from hindered phenols (11 3) still takes place (Scheme 11) (61, 62). The superoxo complex (9) must therefore have been responsible, but the analogy with dioxygenases goes no further as there was no ensuing reaction between (10) and (3) (Scheme 11) (61). 

The binuclear -peroxo complex can be oxidized further by a number of reagents to yield the corresponding /x-superoxo complex [45]. An efficient procedure for the preparation of the decamine M Superoxo complex from the /x-peroxo species utilizes ammonium persulfate as the oxidant, equation (11). 

Also, some of these bisphenolic chelates and polychelates were found m bind dioxygen. The Co " " polychelates reversibly form mononuclear superoxo complexes, while the low molecular chelates form binuclear i-peroxo complexes. 

Barraclough CG, Eawrance GA, Fay PA. 1978. Characterization of binuclear /r-peroxo and /Li-superoxo cobalt(III) amine complexes from Raman spectroscopy. Inorg Chem 17 3317. 

Strekas TC, Spiro TG. 1975. Resonance Raman spectra of superoxide-bridged binuclear complexes. p,-Superoxo-decacyanodicobaltate(5—) and /n-superoxo-decaamminedicobalt (5 +). Inorg Chem 14 1421. 

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. 

Recent reviews on the chemistry of metal-dioxygen complexes with particular relevance to cobalt systems include a number dealing with general properties,636,634 1 binuclear superoxo and peroxo complexes,642,643 reversible oxygenation,644-646 complex stability,647,448 catalytic oxidation649,650 and electronic651 and EPR652 spectral properties. 

---