Water-soluble cobalt(II) complexes of NN′-substituted bis(salicylaldimine-5-sulphonic acids). Oxygen-carrying properties and conversion into cobalt(III) organometallic compounds

The cobalt(II) complexes of a series of NN′-substituted bis(salicylaldiminesulphonic acids) L =–O3SC6H3(O–)–CHN–R–NCH–(O–)C6H3SO3– with R =(CH2)2, (CH2)3, CH2CH(CH3), and o-C6H4 have been prepared as water-soluble sodium salts, Na2[CoL]. Apart from the spin-free (CH2)3 complex, the remaining spin-paired compounds can be converted into water-soluble organometallic cobalt(III) derivatives. The same cobalt(II) compounds also react readily with oxygen at room temperature to yield mixtures of the superoxo-type [CoL(O2)(OH2)] and peroxo-type [{CoL(OH2)}2(O2)] complexes. The formation of superoxo-type species is reversible at room temperature while the peroxo-species require higher temperatures for dissociation. In the solid state Na2[Co-(SO3-salen)][SO3-salen =NN′-ethylenebis(salicylaldimine-5-sulphonate)] and its ethylenediamine adduct also react to form complexes of the superoxo-type.