Development of a Catalytic Electron Transfer System Mediated by Transition Metal Ate Complexes:  Applicability and Tunability of Electron-Releasing Potential for Organic Transformations

We have developed a catalytic electron transfer (ET) system composed of a transition metal ate complex (Me₃M(II)Li; M = Co(II), Mn(II), Fe(II)) and magnesium. This system (catalytic Me₃M(II)Li/Mg) turned out to be effective for various ET reactions, such as the desulfonylation of N-phenylsulfonyl amides, and others (the chemoselective cleavage of O-allyl groups, the reduction of nitro groups, the partial reduction of diketones, and the reductive coupling of diphenyliodonium salt). The ET ability of this system can be tuned by changing the ligands of the ate complexes. This tunability was experimentally and electrochemically demonstrated:  alkoxy-ligated and dianion-type ET ate complexes showed attenuated and enhanced reducing abilities, respectively. The modification of the ET abilities was evaluated by means of electrochemical measurements and chemical reactions. These results provide a basis for the design of various tailor-made ET ate complexes.