ELECTRONIC AND KINETIC ISOTOPE EFFECTS ON THE ELECTROOXIDATION OF BENZYL ALCOHOLS BY A MONOXO RUTHENIUM(V) COMPLEX OF TETRAMETHYLCYCLAM

The electrooxidation of substituted benzyl alcohols by trans-[Ru(V)(TM C)(O)(NCO)]2+ (TMC = ,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane ) was studied in acetonitrile by rotating disc voltammetry. The second order rate constant between Ru(V)=O and the benzyl alcohols increases in the presence of electron donating substituents and decreases in th e presence of electron withdrawing groups. A linear Hammett plot with a slope of -2.0 was obtained. The large negative reaction constant is consistent with a build up of positive charge at the alcohol in the tr ansition state. The primary kinetic isotope effect (k(H)/k(D)) in benz yl alcohol oxidation was determined to be 4.1. The results are consist ent with a mechanism involving hydrogen atom abstraction by the oxo li gand on the ruthenium complex.