“Redox‐Switch” Catalysis of CC Bond Formation with H2: One‐Electron Reduction of the Trityl Cation

Different products are formed from the electron transfer reaction between the ruthenium hydride 1 and the trityl cation when 1 is employed as a “redoxswitch” catalyst or as stoichiometric reducing agent. In the first case 1 converts H2 into a one-electron reducing agent for CC bond formation, thus yielding the product known as Gomberg's dimer. In contrast, only triphenylmethane is produced in the stoichiometric reactions, by an electron-transfer/hydride-transfer mechanism.