Kinetics and mechanistic studies of the interaction of thiosulfate with cis-diaqua-bis[1-alkyl-2-(arylazo)imidazole]ruthenium(II) complexes

摘要: Abstract The nucleophilic substitution reaction of S2O32− with [Ru(HaaiR′)2(OH2)2](ClO4)2 (1) [HaaiR′ = 1-alkyl-2-(phenylazo)imidazole] and [Ru(ClaaiR′)2(OH2)2](ClO4)2 (2) [ClaaiR′ = 1-alkyl-2-(chlorophenylazo)imidazole] [where R′ = Me(a), Et(b) or Bz(c)] in acetonitrile–water (50% v/v) medium to yield Na2[Ru(HaaiR′)2(S2O3)2] (3a, 3b 3c) Na2[Ru(ClaaiR′)2(S2O3)2] (4a, 4b 4c) has been studied. products were characterized by microanalytical data spectroscopic techniques (UV–Vis, NMR mass spectroscopy). proceeds two consecutive steps (A → B → C); each step follows first order kinetics respect complex S2O32−, the second rate constant (k′2) is greater than one (k″2). An increase π-acidity ligand increases rate. Thermodynamic parameters, standard enthalpy activation (Δ‡H0) entropy (Δ‡S0), have calculated for both using Eyring equation from variable temperature kinetic studies. low Δ‡H0 large negative Δ‡S0 values indicate an associative mode aqua processes.