title: Equilibrium, kinetic and solvent effect studies on the reactions of [RuIII(Hedta)(H2O)] with thiols.
abstract: The interaction of [Ru(III)(edta)(H(2)O)](-) with a series of selected thiols having extra functional groups was investigated potentiometrically and kinetically. The pK(a) values of the uncoordinated carboxylic acid group and coordinated water molecule are 3.12 and 7.41, respectively, in aqueous solution at 25 degrees C and 0.1 M ionic strength. The formation constants of the complexes were determined in the pH range 3-9, and the concentration distribution of the various complex species was evaluated as a function of pH. The effect of dioxane on the pK(a) values of [Ru(III)(Hedta)(H(2)O)] and the formation constants of the corresponding thiol complexes is presented. The study also provides mechanistic information on the reaction of [Ru(III)(edta)(H(2)O)](-) with the thiols. The low values of DeltaH(not equal) and negative values of DeltaS(not equal) and DeltaV(not equal) for the substitution reactions of [Ru(III)(edta)(H(2)O)](-) clearly support the associative character of the substitution process.
authors.affiliation: Department of Chemistry, Faculty of Science, Cairo University, Giza, Egypt.
authors.forename: Mohamed M
authors.initials: MM
authors.lastname: Shoukry
authors.forename: Mohamed R
authors.initials: MR
authors.lastname: Shehata
authors.forename: Mohamed S A
authors.initials: MS
authors.lastname: Hamza
authors.forename: Rudi
authors.initials: R
authors.lastname: van Eldik
mesh_terms: D004146:Dioxanes / Q000737:chemistry; D004492:Edetic Acid / Q000031:analogs & derivatives* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008024:Ligands; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry*; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D014867:Water / Q000737:chemistry*
chemical_list: D004146:Dioxanes; D008024:Ligands; D009942:Organometallic Compounds; D012997:Solvents; D013438:Sulfhydryl Compounds; D014867:Water; D012428:Ruthenium; D004492:Edetic Acid; C025223:1,4-dioxane; C026060:N-(hydroxyethyl)ethylenediaminetriacetic acid