Ring opening and displacement by chloride of the bidentate chelate ligand from dichloro[pyridine-2-(α-methoxymethanolato)]gold(III) -: A kinetic and mechanistic study

The kinetics of ring opening and displacement of the bidentate chelate ligand from dichloro[pyridine-2-(alpha-methoxymethanolato) ] gold(III) [Au(N-O)Cl-2] (1) have been studied spectrophotometrically in methanol/water (95:5, v/v) at 25 degrees C and constant ionic strength (I = 1 moldm(-3), LiClO4). In the presence of LiCl and perchloric acid the reaction consists of a pre-equilibrium protonation of the coordinated oxygen followed first by ring opening at oxygen accompanied by the entry of chloride or solvent and fast acetalisation of the hemiacetalic form of the ligand to give [AuCl3(N-OMe)], and then by displacement of the N-bonded ligand to give [AuCl4](-). The ligand is not displaced in the absence of chloride and no reaction is observed in the presence of chloride alone. (c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006.