Interaction of sulfur dioxide and cyanide with cobalt(II) tetrasulfophthalocyanine in aqueous media

Kinetic and equilibrium studies for the coordination of cyanide or sulfur dioxide to the cobalt(II) tetrasulfophthalocyanine ([CoTSPc](4-)) complex are reported. The equilibrium constant for the coordination of the cyanide under pH I I conditions and an oxygen atmosphere, and the formation of [(CN-)(2)Co(III)TSPc](5-) species, was found to be 2.1 x 101 dm(3) mol(-1) and the rate constant, k(r) was found to be 7.4 dm(3) mol(-1) s(-1). Similarly, the coordination of SO2 to [CoTSPc](4) occurred with an equilibrium constant of 8.7 x 10(1) dm(3) mol(-1) and a rate constant of 2.1 x 10(2) dm(3) mol(-1) s(-1), at pH 11. These rate and equilibrium constants represent the coordination of the second cyanide or sulfur dioxide ligands to the [CoTSPc](4) species. Coordination of the first ligand occurred faster than that of the second ligand in both cases. The coordination is accompanied by the oxidation of the central Co(II) metal with the formation of a Co(III) tetrasulfophathalocyanine species. (C) 2002 Elsevier Science Ltd. All rights reserved.