Bridged Ru II -Rh III Complexes

The Ru(II)-Rh(III) cyanide-bridged complexes show absorptions that are characteristic for ruthenium and rhodium polyazine complexes. The electronic absorption spectra of a series of cyanide-bridged Ru(H)-Rh(ni) complexes recorded in DMSO-H2O solutions correlate well with the electrochemical properties. Coordination of a second Rh(III) shifts the lowest energy transition, which is Ru bpy MLCT in nature, to higher energy in [(bpy)2Ru (CN)Rh(NH3)5 2] relative to [(bpy)2(CN)Ru(CN)Rh(NH3)5] . This positive shift is consistent with the stabilization of the Ru(djt) orbitals of [(bpy)2Ru (CN)Rh(NH3)5 2] and correlates well with the electrochemistry where the Ru° oxidation moves to more positive potential with Rhflll) addition. The of 

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The electrochemical properties of the dpp-bridged Ru(II)-Rh(III) complex provides insight into the orbital energetics. The reductive electrochemistry of [(bpy)2Ru(dpp)Rh(bpy)2] shows an irreversible reduction at —0.65 V (Table ) DeArmond has shown that reductive electrochemistry of [Rh(bpy)3] consists of a quasi-reversible reduction at ca. —0.80 V in acetonitrile attributed to reduction. The irreversible nature of this... 

E. Ru(II)-Rh(III) Complexes Bridged with a Flexible Spacer [(Me2phen)2Ru(Mebpy-CH2-CH2-Mebpy)Rh(Me2bpy)2] ... 

The reactions of diferrocenoyhnethane and of spacer-bridged bis-, tris- and tetrakis (ferrocenoyl)- ,3-diketones with NaOMe, KH or chloro complexes of Pd(II), Ru(II), Rh(III) and Ir(III) in the presence of K2CO3 afford a series of mono-, bis-, tris- and tetrakis(/l -diketonato) complexes . 

Balzani et al. have reported the electrochemical, photochemical, and photophysical properties of many dpp-bridged complexes. The Ru(II)/Os(II)-Rh(III) complexes, [Ru (dpp)Rh(ppy)2 3](PFe)5 and [Os dpp)Rh(ppy)2 3](PF6)5 (Fig. 17) (ppy = phenylpyridine anion), reported by Balzani et al. incorporate the dpp BL and a C-N type cyclometallating terminal ligand (TL) in the construction of complex molecular architectures. The dpp BL provides electronic coupling of the bridged metals. The tris(bidentate) coordination environments of rhodium inhibit reactivity at this site. 

The rate and activation parameters for the intramolecular electron transfers from Os(II)(NH3)5 to Ru(III)(NH3)5 across oligoproline peptide bridges have been determined. The rate constants decrease from 3.1 x 10 s to 50 s as the number of proline units is increase from 1 to 4, and the metal-metal separation distance increases from 12 to 21 A. A time-correlated single photon counting method was employed to investigate the kinetics of the forward [ Ru(II)- Rh(III)] and reverse [Ru(III)<-Rh(II)] intramolecular electron transfer reactions within covalently linked Ru/Rh polypyridine complexes in aqueous, acetonitrile, and methanol solvents. The rate constants for the outer-sphere electron transfer reactions of [Ru(edta)pyz] and... 

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