THE REACTIVITY OF CATIONIC PLATINUM(II) COMPLEXES CONTAINING THE TRIDENTATE LIGAND BIS(2-PYRIDYLMETHYL)SULPHIDE

The kinetics of the displacement of coordinated nitrogen donor bases ( L) by chloride from complexes of the type [Pt(NSN)(L)](2+) [NSN = bis( 2-pyridylmethyl) sulphide; L = a series of pyridines, isoquinoline and NH3] as well as chloride substitution from the substrate [Pt(NSN)Cl]( +) by Br- and I- have been studied in methanol at 25 degrees C and con stant ionic strength and compared with those of the corresponding plat inum(II) complexes containing the 2,6-bis(methylsulphanylmethyl)pyridi ne tridentate ligand. The two-term rate law usually found in substitut ions at square-planar platinum(II) complexes is obeyed. Both the first and second-order rate constants for the displacement of L decrease as the basicity of the leaving group increases. pi interactions between coordinated pyridines and the metal centre are suggested by comparison of their lability with that of ammonia as well as with that of para-s ubstituted pyridines with enhanced pi system. Steric hindrance on the leaving base also significantly decreases the reactivity.