ELECTROCHEMISTRY OF MOLYBDENUM IMIDES - CLEAVAGE OF MOLYBDENUM-NITROGEN TRIPLE BONDS TO RELEASE AMMONIA OR AMINES

The electrochemical reduction of molybdenum(IV) alkylimides trans-[MoX (NR)(dppe)(2)](+) (X = halide, R = alkyl, dppe = Ph2PCH2CH2PPh2) proce eded by two pathways. In the absence of a source of protons, moderatel y stable five-co-ordinate molybdenum(II) imides are formed via an init ial single-electron transfer followed by rate-determining loss of the trans-halide ligand and an additional electron transfer. In the presen ce of a source of protons; molybdenum-halide bond cleavage is intercep ted by protonation at N which gives an amide intermediate. Further ele ctron-transfer chemistry liberates amines and yields a dinitrogen comp lex in an overall four-electron process. Molybdenum(IV) imides trans-[ MoX(NH)(dppe)(2)](+) were reduced to amide intermediates with the pare nt imide cation providing the source of protons and water probably act s as a proton-transfer relay. The amide has two fates; it is either co nverted into a nitride by hydrogen loss or, at a potential which encom passes its further reduction, yields ammonia and a dinitrogen complex.