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

Abstract

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.