Ruthenium(II) Dichloride Complexes of Chiral, Tetradentate Aminosulfoxide Ligands: Stereoisomerism and Redox-Induced Linkage Isomerism

Ruthenium­(II) dichloride complexes of two chiral tetradentate aminosulfoxide ligands, varying only in the N–N linker, were synthesized. With each ligand, two major isomers formed, and these were structurally assigned and characterized through a combination of NMR and UV–vis spectroscopies, X-ray crystallography, and density functional theory calculations. The <i>cis</i>-β geometric isomer was formed by each ligand, whereas the <i>trans</i> and <i>cis</i>-α geometric isomers were significant components for one ligand only. Cyclic voltammetry studies show that only the <i>cis</i>-β isomers undergo linkage isomerism upon oxidation to ruthenium­(III), whereas the <i>trans</i> and <i>cis</i>-α isomers show simple reversible redox couples.