Kinetics and mechanism of Ru(III)-catalysed oxidation of organic sulphides and triphenylphosphine by N-methylmorpholine N-oxide.

The selective oxidation of thioethers to sulphoxides and of PPh to PPhO can be effected by NMO in DMF as solvent in the presence of Ru(III) chloride as catalyst. Kinetic investigations indicate that the orders with respect to the catalyst and oxidant are one each. The order with respect to the substrate is variable being fractional order at low concentrations and zero at high concentrations. Spectrophotometric studies reveal the formation of a 1:1 complex between the substrate and the catalyst. A mechanism consistent with the above observations has been proposed and verified. [ABSTRACT FROM AUTHOR]