The Lewis-acidity of square-planar nickel(II) complexes. III. A kinetic study of the effects of substituents on the addition of 1,10-Phenanthroline to Bis(monothioacetylacetonato)nickel(II) and Bis(dithiophosphato)nickel(II) complexes in toluene

Abstract

The second-order rate constants and activation parameters for the addition of 1,10-phenanthroline to bis(dialkyldithiophosphato)nickel(II) complexes and substituted bis(monothioacetylacetonato)-nickel(II) complexes in toluene have been measured. Rate constants are in the range 10²-10⁸ 1. mol^-1 s^-1 at 25°C, while ΔH^‡ is in the range 10-50 kJ mol^-1 and ΔS^‡ is in the range from -30 to -110 J mol^-1 K^-1. The higher rate constants, smaller ΔH^‡ and more negative ΔS‡ values are associated with complexes with electron- withdrawing substituents. The results are related to the thermo- dynamics of adduct formation, the inductive effects of the substituents and the pK_a of the ligands.