Kinetics and mechanism of the oxidation of phosphinic, phenylphosphinic and phosphorous acids by benzyltrimethylammonium dichloroiodate

Abstract

Oxidation of lower phosphorus oxyacids by benzyltrimethylammonium dichloroiodate (BTACI), in the presence of zinc chloride, resulted in the formation of the corresponding oxyacids with phosphorus in a higher oxidation state. The reaction is first order with respect to the concentration of BTACI, oxyacid and zinc chloride. The reaction exhibited the presence of a substantial kinetic isotope effect. Addition of benzyltrimethylammonium chloride enhances the reaction rate. It is proposed that the reactive oxidizing species is [PhCH2Me3N]+ [Zn2Cl6]−2I+. It has been shown that the pentacoordinated tautomer of the phosphorus oxyacid is the reactive reductant. A mechanism involving a hydride-ion transfer from the P-H bond to the oxidant in the rate-determining step has been postulated.