Linkage isomerism in penta-ammineruthenium(II),(III) complexes of benzotriazole

Abstract

The linkage isomerism in penta-ammine(benzotriazole)ruthenium(II),(III) complexes has been investigated in aqueous solution, using spectroelectrochemistry, cyclic voltammetry, and n.m.r. (¹H, ¹³C) spectroscopy. The deprotonation of the Ru^II complex (pK_a= 6.4) leads to a single, C_2v isomer which can be reversibly oxidized to Ru^III, with E°=–0:127 V versus normal hydrogen electrode. The oxidized complex isomerizes within the time-scale of the cyclic voltammetry, forming a mixture of C_s(N¹) and C_2v(N²) linkage isomers, with an equilibrium constant of 1.4 favouring the symmetric species. The analysis of the isomerization reactions in terms of a chemical– electrochemical scheme supports an intramolecular mechanism, involving π-bonded activated complexes.