Fast reactions at planar four-co-ordinate complexes. Part 3. Kinetics and mechanism of substitution reactions of sterically hindered aniono-(mesityl)bis(triethylphosphine)nickel(II) complexes

Abstract

The kinetics of displacement of ligand X from the complexes trans-[Ni(PEt₃)₂(C₆H₂Me₃-2,4.6)X] by a variety of nucleophiles Y^–(X = Cl, Br, I, N₃, or NO₂; Y = Cl, Br, I, NO₂, SCN, or N₃) has been studied in ethanol at 25 °C. The results suggest that the substitution proceeds by means of two competing paths, one associative and the other solvolytic. The kinetic parameters are compared with those relating to the reactions of the analogous complexes trans-[Ni(PEt₃)₂(C₆H₄Me-o)X] and trans-[Pt(PEt₃)₂R(Cl)](R = mesityl or o-tolyl) under the same experimental conditions.