Rates and mechanisms of substitution reactions of square-planar dithiocarbamate and dithiophosphate complexes of the nickel triad in methanol

Abstract

Rate constants for the substitution reactions of square-planar dithiophosphate and dithiocarbamate complexes of Ni^II, Pd^II, and Pt^II, with ethylenediamine and cyanide ion as nucleophiles, have been measured in methanol at an ionic strength of 0.1 mol dm^–3 sodium perchlorate. A general mechanism is proposed to account for the kinetic data. The order of the reactivity of the complexes is approximately Ni : Pd : Pt = 10⁵ : 10³ : 1. The results are compared with those obtained in previous investigations and are interpreted in terms of the stabilities of the five-co- ordinate species which are formed prior to substitution.