Pentamethylcyclopentadienyl-rhodium bipyridine

Several dyes or transition-metal complexes can be used as redox mediators in indirect electrolyses. Pentamethylcyclopentadienyl-rhodium(bipyridine) complexes [Cp Rhnl(bpy)(H20)]2+ 9 [33], which were pioneered and intensively studied by Steckhan et al. [34—36], are very versatile catalysts for the reduction of cofactors. 

Cp = pentamethylcyclopentadienyl, bpy = 2,2 -bipyridine) as the catalyst (43). The reaction takes place at ambient temperature, and no CO was detected in the H2-CO2 mixture. A rhodium hydride complex was identified in the catalytic cycle, which undergoes a rapid H/D exchange in presence of D2O. This result is consistent with the proposed rate-determining step, which is y3-hydrogen elimination from the formate complex (Fig. 1). 

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