Synthesis, reactivities and electrochemistry of trans-dioxoruthenium(VI) complexes of π-aromatic diimines

Abstract

The synthesis and electrochemistry of trans-[RuIII(L) 2(OH)(H2O)][CIO4]2 [L = 1,10-phenanthroline (phen) or 5,5′-dimethyl-2,2′-bipyridine(dmbipy)] are described. Oxidation of trans-[RuIII(L)2(OH)(H 2O)]2+ by CeIV in water gave trans-[Ru VI(L)2O2]2+ which were isolated as the yellow perchlorate salts. The complex trans-[RuVI(dmbipy) 2O2][CIO4]2 is a powerful oxidant with E° (RuVI-RuIV) = 1.0 V vs. saturated calomel electrode at pH 1.0. In acetonitrile or acetone, it oxidizes alcohols to ketones/aldehydes, tetrahydrofuran to γ-butyrolactone, alkenes to epoxides and saturated or aromatic hydrocarbons to alcohols/ketones. Oxidation of saturated alkanes occurs preferentially at the tertiary C-H bond. In the presence of CCl4, cyclohexane is oxidized to cyclohexyl chloride instead of cyclohexanone. The mechanisms of alcohol and cyclohexane oxidation were investigated by kinetic experiments and by isotope labelling studies.