Reactivity of metal chelates of sulphur containing ligands towards lewis bases. Part II. reaction of Bis(S-methyl-N-arlidenehydrazinecarbodithioate)nickel(II) chelates with pyridines and 2,2′-bipyridyl

Abstract

The reaction of bis(S-methyl-N-arlidenehydrazinecarbodithioate)nickel(II) chelates with pyridine, 3-methylpyridine, 4-methylpyridine and 2,2′-bipyridyl has been studied in benzene solution. The stability constants as well as the thermodynamic parameters for adduct formation were measured spectrophotometrically. The obtained results suggest the formation of octahedral bis-adducts with unidentate pyridines, while cis-octahedral monoadducts are formed from the reaction of 2,2′-bipyridyl with p-methoxy, p-methyl and unsubstituted chelates. The p-chloro derivative, however, forms a five-coordinate monoadduct where one of the hydrazone molecules behaves as unidentate ligand. The kinetics of bipyridyl adduct formation were followed by means of stopped flow techniques. The kinetic data suggest the rapid formation of five-coordinate intermediate, in which the bipyridyl molecule reacts as a unidentate ligand, followed by slow rate determining bipyridyl ring closure.