Metal ion-sulfur(IV) chemistry. 1. Structure and thermodynamics of transient copper(II)-sulfur(IV) complexes

The stability constant for the formation of CuSO_3 has been determined spectroscopically to be K = (1.8 ± 0.6) x 10^4 M^(-1) at µ = 0.4 M. The magnitude of this constant is large compared to that of the stability constants of simple inorganic complexes of Cu(II) such as CuSO_4, CuCl^+, CuClO^+, and CuNO_3^+. Infrared and Raman spectroscopic measurements indicate that sulfite ion binds to copper through both sulfur and oxygen. Comparisons of CuSO_3 complexes with other first-row transition metal-sulfite complexes are made, and the implications for the atmospheric chemistry of S(IV) are discussed.