Synergistic Effect of [Ru(III) + Ir(III)] in N-Bromosuccinimide Reaction with Certain Aliphatic Ketones: A Kinetic Study

Abstract

Dramatic rate enhancements have been observed in the oxidation of acetone (MMK), ethyl methyl ketone (EMK), and isobutyl methyl ketone (IBMK) by N-bromosuccinimide (NBS) in the presence of a mixture of metal ions [Ru(III) + Ir(III)]. The rate of oxidation in the the [Ru(III) + Ir(III)] system is much faster than either in the Ru(III) or in Ir(III) catalyzed system. The order in [NBS] was found to be zero both in catalyzed as well as uncatalyzed reactions. However, the order in [ketone] changed from unity to a fractional one in metal ion catalyzed systems. On the basis of kinetic features, the most plausible mechanism involving the oxidation of [Ir(III)-ketone] by Ru(III) to give [Ir(V)-ketone] and Ru(I) in the rate limiting step is proposed. Ru(I) thus formed is oxidized by NBS to Ru(III) in a fast step is discussed and individual rate parameters were evaluated.