Isonicotinamide, ruthenium complex

In order to obtain further information on the magnitude of the overall reaction volume and the location of the transition state along the reaction coordinate, a series of intermolecular electron-transfer reactions of cytochrome c with pentaammineruthenium complexes were studied, where the sixth ligand on the ruthenium complex was selected in such a way that the overall driving force was low enough so that the reaction kinetics could be studied in both directions (153, 154). The selected substituents were isonicotinamide (isn), 4-ethylpyr-idine (etpy), pyridine (py), and 3,5-lutidine (lut). The overall reaction can be formulated as... 

Unusual dinuclear complexes are often formed by the oxidation of the [Cr(HaO) ion with an inert metal complex. The species [(HaO)5Cr (isonicotinamide)Ru"-(NH3)6] + is formed in this way, in which the isonicotinamide bridges between the two metal ions, being co-ordinated to ruthenium(n) at the heterocyclic pyridine nitrogen atom and to chromium(in) at the carbonyl oxygen atom. The kinetics of the decomposition of this dinuclear species have been investigated in the presence of an acidic aqueous chromium(n) catalyst. The observed rate constant. A, is given by A = Ao + A-i/[H+] + A-2[Cri ]/[H+l... 

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