A Personal Account on Inorganic Reaction Mechanisms

The presented Review is focused on the latest research in the field of inorganic chemistry performed by the van Eldik group and his collaborators. The first part of the manuscript concentrates on the interaction of nitric oxide and its derivatives with biologically important compounds. We summarized mechanistic information on the interaction between model porphyrin systems (microperoxidase) and NO as well as the recent studies on the formation of nitrosylcobalamin (CblNO). The following sections cover the characterization of the Ru(II)/Ru(III) mixed-valence ion-pair complexes, including Ru(II)/Ru(III)(edta) complexes. The last part concerns the latest mechanistic information on the DFT techniques applications. Each section presents the most important results with the mechanistic interpretations.

Inorganic reaction mechanisms. A personal journey

This review covers highlights of the work performed in the van Eldik group on inorganic reaction mechanisms over the past two decades in the form of a personal journey. Topics that are covered include, from NO to HNO chemistry, peroxide activation in model porphyrin and enzymatic systems, the wonder-world of Ru^III(edta) chemistry, redox chemistry of Ru(iii) complexes, Ru(ii) polypyridyl complexes and their application, relevant physicochemical properties and reaction mechanisms in ionic liquids, and mechanistic insight from computational chemistry. In each of these sections, typical examples of mechanistic studies are presented in reference to related work reported in the literature.

Reaction of [RuIII(edta)(H2O)]? with H2O2 in aqueous solution. Kinetic and mechanistic investigation

The reaction of [Ru(III)(edta)(H(2)O)](-) (1) (edta = ethylenediaminetetraacetate) with hydrogen peroxide was studied kinetically as a function of [H(2)O(2)], temperature (5-35 degrees C) and pressure (1-1300 atm) at a fixed pH of 5.1 using stopped-flow techniques. The reaction was found to consist of two steps involving the rapid formation of a [Ru(III)(edta)(OOH)](2-) intermediate which subsequently undergoes parallel heterolytic and homolytic cleavage to produce [(edta)Ru(V)=O](-) (45%) and [(edta)Ru(IV)(OH)](-) (55%), respectively. The water soluble trap, 2,2'-azobis(3-ethylbenzithiazoline-6-sulfonate) (ABTS), was employed to substantiate the mechanistic proposal. Reactions were carried out under pseudo-first conditions for [ABTS] >> [HOBr] >> [1], and were monitored as a function of time for the formation of the one-electron oxidation product ABTS* (+). A detailed mechanism in agreement with the rate and activation parameters is presented, and the results are discussed with reference to data reported for the corresponding [Fe(III)(edta)(H(2)O)](-)/H(2)O(2) system.

Equilibrium, kinetic and solvent effect studies on the reactions of [RuIII(Hedta)(H2O)] with thiols

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.