The role of the non-participating groups in substitution reactions at cationic Pt(II) complexes containing tridentate chelating nitrogen donors. Crystal structure of {Pt[bis(2-pyridylmethyl)amine](py)} (CF3SO3)(2)

摘要

Kinetic measurements on the displacement of chloride with the nucleophiles Br-, I- and N (N = a number of isosteric pyridines and morpholine) from the substrates [Pt(NNN)Cl](+) [NNN = bis(2-pyridylmethyl)amine (bpma): 2,6-bis(aminomethyl)pyridine (dap); diethylenetriamine (dien)] have been carried out in methanol at 25 degreesC. The results, compared with those previously obtained on the complex [Pt(terpy)Cl](+) (terpy = 2,2':6',2"-terpyridine) are discussed in terms of reactivity and discrimination ability of the reaction centre. The significant differences in kinetic behaviour along the series are particularly related to the presence of pyridine rings in the non-participating chelate ligand and steric effects. The study of the reverse process, i.e. the displacement of N with a chloride ion from the complexes [Pt(NNN)(N)](2+), allows the determination of the equilibrium constants from the ratio of the rate constants. The crystal structure of [Pt(bpma)(py)](CF3SO3)(2) has been determined by the X-ray diffraction technique. It consists of essentially SP (square-planar) [Pt(bpma)(py)](2+) cations. The plane through the pyridine ring makes an angle of 86.1(3)degrees with that of Pt and the three nitrogen atoms of bpma. The packing is characterised by a hydrogen bond between the N-H of the ligand and one oxygen of a triflate anion. (C) 2001 Elsevier Science Ltd. All rights reserved. [References: 29]