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The heterobimetallic complexes CpRu(PPh3)(μ-Cl)(μ-dppm)PdCl2 (1) [dppm = bis(diphenylphosphino)methane], CpRu(PPh3)Cl(μ-dppm)AuCl (2), and CpRu(PPh3)(μ-Cl)(μ-dppm)PtCl2 (3) were synthesized by the reaction of CpRu(PPh3)Cl(η1-dppm) (4) with Pd(COD)Cl2, AuPPh3Cl, and Pt(COD)Cl2, respectively. Compounds 1 and 2 were characterized by X-ray crystallography. Electrochemical oxidation of CH3OH in the presence of 1, 2, or 3 leads to considerable enhancement of the oxidative currents and formation of the organic products CH2(OCH3)2 and HCOOCH3. Addition of water increases both the current and the proportion of the more highly oxidized product, HCOOCH3. Current efficiencies obtained with heterobinuclear complexes 1−3 were significantly higher than those obtained using the model compound CpRuCl(η2-dppm) (5) as catalyst.

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Replacing a tungsten oxide group of phosphotungstic acid with a Rh(II) acetate dimer yielded a species, Rh 2 POM, that catalyzed the electrochemical oxidation of L-methionine (L-Met), L-cystine, and As(III). The electrocatalytic activity of Rh 2 POM was greater than that of the simple Rh(II) acetate dimer in homogeneous solution. A conducting carbon-composite electrode (CCE) comprising Rh 2 POM and carbon powder in a silica matrix prepared by sol-gel chemistry was catalytically active over the pH range 2-10. The CCEs produced voltammetric responses toward L-Met and L-cystine that were pH independent over the above range and were stable for at least 4 months under dry storage. If passivated, the catalytic activity was reproducibly generated by polishing. For example, a relative standard deviation of 2.9 % (5 points) was obtained when the surface was polished between cyclic voltammetric experiments on 5.0 mM L-Met at pH 7.4. A least squares fit of flow injection amperometric data obtained over the range 5-156 mM L-Met (7 points) yielded the following: slope, 0.85 mA mM ¹1 ; intercept, 0.05 mA; and r = 0.995. The detection limit was 2.3 mM.