Study of cyanoaquonitrosyl complexes of chromium. V. Electrochemical properties of the cyanide bond isomers of NO(H 2O) 4CrCN + and of their complexes with silver(I) and a study of their equilibria

Abstract

The equilibrium of the CN bond isomers of NO(H 2O) 4Cr(CN) + was studied polarographically using the fast formation of the NO(H 2O) 4CrNC + complex with Hg 2+. The isomerization equilibrium constant. Q i = [NO(H 2O) 4CrCN +]/[NO(H 2O) 4CrNC +] = (2.6 ± 0.1) X 10 2, and the deprotonation equilibium constant, K a = [NO(H 2O) 4CrNC + [H +]/ [NO(H 2O) 4CrNCH 2+] = (2.5 ± 0.2) X 10 −2M, (both values at 25 °C and an ionic strength of 1 M), obtained from these mesurements are in a good agreement with the values obtained by other methods. The electrochemical reactions of {NO(H 2O) 4CrNC} 2Ag 3+ were described and explained from the viewpoint of the stochiometry and the mechanim of the formation reaction. The schemes proposed are based on voltammetric and coulometric measurements. From an analysis of the polarographic limiting diffussion current for the reduction of complexes Ag(I), the value of the equilibrium constant, Q = [NO(H 2O) 4CrNCAg 2+] 2/[Ag +][{NO(H 2O) 4CrNC} 2Ag 3+] = (0.12 ± 0.08), was obtained for 25 °C and an ionic strength of 1 M.