Alternative reaction path for the photochemical reaction of tris(oxalato)cobaltate(III) in various aprotic solvents in the presence of oxygen

Abstract The photochemistry of the tris(oxalato)cobaltate(III) complex in N , N -dimethylformamide, acetonitrile, pyridine and dichloromethane was studied. In oxygen-free solutions a photoredox decomposition reaction occurs, similar to that in water and in the solid state. The quantum yield of this reaction in N , N -dimethylformamide, acetonitrile and pyridine for 313 nm light and at 293 K was determined. In oxygen-containing solutions the reaction course in quite different. This study focused on the product formed in the initial stage of the photochemical reaction. In the different solvents the photolysis product was the same and was identified as the side-on peroxodioxalatocobaltate(III) complex. This complex could be isolated by means of column separation only in N , N -dimethylformamide. The complex decomposes in strong polar and in acidic media. A reaction path for the photolysis in the considered solvents is presented, based on the mechanism of the photochemical reaction of tris(oxalato)cobaltate(III) in water. The experimental results are best explained by assuming that the first step of the photochemical reaction is the same in the absence of oxygen. The secondary steps, which are thermal reactions, are different depending on the absence or presence of oxygen in the solution.