EFFECT OF THE ELECTRODE MATERIAL ON THE REACTION ROUTE FOR THE ELECTROREDUCTION OF METAL-COMPLEXES CONTAINING LIGANDS WITH ACIDIC C-H BONDS- THE CATION OF NE]-(METHYLIMIDE)MOLYBDENUM,[CLMO(DPPE)(2)NCH3](+)

Low-temperature cyclic voltammetry with ultramicroelectrodes was used to study the electroreduction of the methylimide complex of [ClMo(dppe )(2)NCH3](+) [1(+); dppe stands for bis(diphenylphosphino)ethane] in a bsolute tetrahydrofurane (THF). The 1(+) complex was shown to undergo reversible one-electron reduction to [ClMo(dppe)(2)NCH3] (1), whose fa te depends on the nature of the electrode material. At Hg and vitreous carbon electrodes in a nitrogen atmosphere, the 1 intermediate underg oes irreversible four-electron reduction to [Mo(N-2)(2)(dppe)(2)] and methylamine. Being a strong base, the electrogenerated complex 1 depro tonates the starting complex 1(+) in the course of a parallel reaction to form the methylene amide complex [ClMo(dppe)(2)NCH2] (2). The Pt e lectrode exhibits no further reduction of the intermediate 1; instead, a wave of catalytic hydrogen evolution is observed. It is assumed tha t the key step of the hydrogen evolution process is platinum-catalyzed abstraction of a hydrogen atom from 1, which was turned to 2. Lowerin g the temperature allows the reversible oxidation of 1(+) to the [ClMo (dppe)(2)NCH3](2+) dication to be observed.