The exchange of pyridine on bis-pyridine adducts of square-planar nickel(II) complexes containing dithiocarbamate, xanthate, dithiophosphate and monothioacetylacetonate ligands. A nitrogen-14 magnetic resonance study

Abstract

14N n.m.r. has been used to measure the rates of pyridine exchange of a series of bis pyridine adducts of square-planar nickel(II) complexes containing dithiocarbamate, xanthate, dithiophosphate and monothioacetylacetonate ligands. Substantial variations in the lability of the coordinated pyridine are observed, k,, at 298 K varying from about 103 to 107 s-1. In the monothioacetylacetonate series the lability of pyridine decreases as the electron withdrawing power of the substituents increases. Both the lability and the sensitivity to substituent effects are greater than for the analogous acetylacetonate derivatives. The relationship between the intrinsic Lewis acidity of the nickel(II) centre in the parent square-planar complexes as measured by equilibrium constants for bis pyridine adduct formation and the lability of pyridine in the adducts is explored.