The Lewis-acidity of square-planar nickel(II) complexes. I. A kinetic and thermodynamic study of the reaction of Bis(O,O-diethyl phosphorodithioato-S,S'-)nickel(II) with bidentate nitrogen donors

Abstract

The kinetics of the addition reaction between bis(O,O-diethyl phosphorodithioato-S,S'-)nicke1(11) and a series of bidentate nitrogen ligands has been examined by stopped-flow techniques. The reactions are first order in ligand and nickel complex with k_f, the second-order rate constant, in the range from 10³ to 10⁶ 1. mol^-1 s^-1 at 25ºC in benzene. Solvent effects on the reaction with 2,2'-bipyridyl are minor. The variation in k_f with ligand is discussed in terms of the steric requirements of the ligands, the bulkiest ligand, 2,9-dimethyl-1,l0-phenanthroline, reacting most slowly. For the ligands 1,l0-phenanthroline and 2,2'-bipyridyl in the more polar solvents, successive displacement of the thiophosphate ligands follows the initial addition step.