HOMOGENEOUS CATALYSIS OF D2–H2O EXCHANGE BY RUTHENIUM (III) CHLORIDE: EVIDENCE FOR THE HETEROLYTIC SPLITTING OF HYDROGEN

Abstract

The prediction, based on earlier studies of the ruthenium(III) chloride catalyzed oxidation of H₂ by iron(III), that in the absence of iron(III) or other oxidants ruthenium(III) chloride should catalyze homogeneously the isotopic exchange between D₂ and H₂O has been confirmed. A kinetic study was made of this exchange reaction in which the dependence of the exchange rate and of the exchange product distribution (HD:H₂ ratio) on the concentrations of ruthenium(III), hydrogen ion, and chloride ion were determined. The results, and in particular the observation that the HD:H₂ ratio of the exchange product increases with the concentrations cf H⁺ and Cl⁻, support the view that the ruthenium (III)-catalyzed oxidation of D₂ by iron(III) and the D₂–H₂O exchange reaction proceed through related mechanisms involving a common rate-determining step in which D₂ is split heterolytically and a deuteridoruthenium(III) complex is formed.