title: The π-acceptor effect in the substitution reactions of tridentate N-donor ligand complexes of platinum(II): a detailed kinetic and mechanistic study.
abstract: The nucleophilic substitution reactions of complexes [Pt{4'-(2'''-CH(3)-phenyl)-2,2':6',2''-terpyridine}Cl]CF(3)SO(3), [CH(3)PhPtCl], [Pt{4'-(2'''-CH(3)-phenyl)-6-(3''-isoquinoyl)-2,2'bipyridine}Cl]SbF(6), [CH(3)PhisoqPtCl], [Pt{2-(2'-pyridyl)-1,10-phenanthroline}Cl]Cl, [pyPhenPtCl], and [Pt(terpyridine)Cl](+), [PtCl] with a series of nucleophiles: thiourea (TU), N,N-dimethylthiourea (DMTU), N,N,N,N-tetramethylthiourea (TMTU), I(-), Br(-), and SCN(-) were studied in 0.1 M LiCF(3)SO(3) in methanol (in the presence of 10 mM LiCl). The reactivity of the investigated complexes follows the order pyPhenPtCl > PtCl > CH(3)PhPtCl > CH(3)PhisoqPtCl. The lability of the chloride ligand is dependent on the strength of π-backbonding properties of the spectator ligands around the platinum centre. The experimental data is strongly supported by DFT calculations. The dependence of the second-order rate constants on concentration of the nucleophiles as well as the large negative values reported for the activation entropy (ΔS(‡)) confirmed an associative mechanism of substitution.
authors: School of Chemistry and Physics, University of KwaZulu-Natal, Pietermaritzburg 3209, South Africa.
authors: Peter
authors: P
authors: Ongoma
authors: Deogratius
authors: D
authors: Jaganyi
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D007546:Isoquinolines / Q000737:chemistry; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D010618:Phenanthrolines / Q000737:chemistry; D010984:Platinum / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D056831:Coordination Complexes; D007546:Isoquinolines; D008024:Ligands; D010618:Phenanthrolines; D010984:Platinum; C039109:isoquinoline; C025205:1,10-phenanthroline