Mixed Valence Chemistry of Pyrimidine Bridged Binuclear Complex of Pentacyanoferrate and Pentaammineruthenium

The pyrimidine bridged binuclear complex (CN)5FepymRu(NH3)5- (I) was prepared in aqueous solution by mixing cquimolar of Fe(CN)5OH23− and Ru(NH3)5pym2+. Its mixed valence state molecule (CN)5FepymRu(NH3)5(II) was obtained upon oxidation of I by one equivalent of peroxydisulfate ion. Both binuclear complexes and corresponding Fe(II) and Ru(II) mononuclear complexes displayed a metal-to-ligand charge transfer absorption in 400–450 nm region. Rate constants of formation and dissociation of I and II were measured, and the values of kf (−103M−1s−1) and kd (−10−3-10−4 s−1) were consistent with kinetic results expected for the substitution of Fe(CN)5OH23− with di- and trivalent ligands. Cyclic voltammetry of I exhibited two one-electron steps of oxidation corresponding to [III, L, II] + e → [II, L, II] and [III, L, III] + e → [III, L, II], respectively. The mixed valence binuclear complex II showed an intervalence band at 955 nm with a molar extinction coefficient 5.80 × 102 M−1cm−1 and a half-width 5100 cm−l. The properties of the IT band conform to Hush's theory. Spectroscopic, electrochemical and kinetic results of II suggest that the mixed valence complex features a trapped - valence formulation with localized oxidation states of Fe(II) and Ru(III).