Spectroscopic Studies of Polynuclear Complexes. III. Characteristics of Some μ-Peroxoammine Cobalt(III) Complexes.

Abstract

Abstract The spectroscopic and chemical properties of various μ-peroxo and μ-superoxo cobalt(III) complexes containing several kinds of polyamine including optically active l-propylenediamine (l-pn) have been studied. The single bridged μ-peroxo complexes have strong absorption peaks at ca. 300 nm, whereas the double-bridged μ-peroxo-μ-amido and μ-peroxo-μ-hydroxo complexes have peaks at ca. 350 nm. The μ-superoxo complexes have two absorption peaks in the visible region at ca. 700 and 480 nm. The former is remarkably stronger for singlebridged species, but both are of almost equal strength for double bridged species. The complexes [LNH3Co(μ-O2(2−))CoNH3L]4+ (L; 2en (ethylenediamine), 2l-pn, and trien(triethylenetetramine)) are spontaneously converted into [LCo(μ-O2(2−), OH)CoL]3+ in water at room temperature. The en ligands in [(dien)(en)Co(μO2(2−))Co(en)(dien)]4+ (dien; diethylenetriamine) are replaced by l-pn in a few days in aqueous solutions containing an excess of l-pn. The absolute configuration of [(l-pn)2Co(μ-O2(2−), OH) Co(l-pn)2]3+ is assigned to be ΔΔ on the basis of circular dichroism spectrum.