The kinetics of the displacement, by chloride, of heterocyclic nitrogen bases (am) from trans-[PtL(am)Cl2](L = C2H4, CO, or PMe3); the effect of steric hindrance in the leaving group on the trans effect of L

Abstract

The kinetics of the reaction, trans-[PtL(am)Cl₂]+ Cl^– [graphic omitted] [PtLCl₃]^–+ Ham⁺(L = C₂H₄, CO, or PMe₃; am = pyridine, 2-methylpyridine, 2,6-dimethylpyridine, or 2,4,6-trimethylpyridine) have been studied in 5% aqueous methanol at 25.0 °C. Only the ethene complexes show a significant dependence on [Cl^–] and this is much reduced on o-methyl substitution in the leaving pyridine. In all cases the reactivity is greatly decreased by steric hindrance in the leaving group. The results are discussed in terms of a general destabilisation of the transition state due to steric crowding, together with a specific effect arising from restrictions on the orientation of the ethene molecule in the transition state.