Light‐driven metallo‐organic catalysis: Intramolecular photoelectron transfer in the heterodinuclear complex 1 facilitates the photocatalytic production of hydrogen and the selective hydrogenation of tolane to give cis‐stilbene. All three well‐coordinated parts of the supramolecular system are essential: the (tbbpy)2Ru fragment as a photoactive unit, the redox‐active bridging ligand as an electron relay and storage site, and the palladium as a catalytically active center.

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The macrocyclic nickel complexes shown in Figure 1 are able to catalyze the electrochemical reduction of CO 2 to oxalate. In the case of the complexes with R 2 ) COOEt or COMe, the overall reaction can be interpreted in terms of an outer-sphere electron-transfer reaction (6) followed by a dimerization of the CO 2 •radical anions ( 7), but the variation of the electron-transfer rate constants with the standard potentials points to a coordinative interaction between the complexes and the CO 2 molecule. Complexes without COOEt or COMe substitution in the R 2 position undergo a fast deactivation reaction (first order with respect to [CO 2 ]) that is even visible in the time scale of the cyclic voltammetric experiments. The results of the cyclic voltammetric investigations could be confirmed in preparative-scale electrolyses where the complex Ni-Etn(Me/COOEt)-Etn proved to be the most active and persistent redox catalyst for the electrochemical reduction of CO 2 to oxalate that has been described so far.