LIGAND-CENTERED CHEMISTRY OF MOLYBDENUM ORGANOIMIDES - FORMATION OF C-C BONDS VIA GENERATION OF NITROGEN YLIDES, STEREOSPECIFIC CONVERSION OF AN ALLYLIMIDE INTO ALKYLVINYLIMIDES, LIBERATION OF CYANOFORMATE OR AMINO-ACID ESTERS

The range of imides trans-[MoCl(NCHR(1)R(2))(dppe)(2)](+) made from th e nitride trans-[MoCl(N)(dppe)(2)] (dppe = Ph(2)PCH(2)CH(2)PPh(2), R(1 ) = H or organic group, R(2) = organic group) has been extended; depro tonation of the imide group at the alpha-carbon gives reactive alkenyl amides which have nitrogen ylide character {Mo=N+-C(-)HR} and these ar e attacked by electrophiles. Stepwise C-1 homologation of a methylimid e to ethyl- and isopropyl-imides can be achieved by successive deproto nation and methylation steps. The crystal structure of the alkenylamid e trans-[MoCl(NCHCO(2)Me)(dppe)(2)] has been determined, as has that o f the imide produced directly from it by C-methylation, trans [MoCl{NC H(Me)CO(2)Me}(dppe)(2)](+). Deprotonation at the alpha-carbon of an al lylimide complex gives a species which is regioselectively and stereos pecifically attacked by electrophiles at the gamma-carbon; when the el ectrophile is the proton the overall reaction corresponds to a 1,3-pro totropic rearrangement of the allylimide to the E-methylvinylimide. El ectroreduction of imides in the presence of a source of protons releas es the free amine; in this way esters of the amino acids glycine and D L-alanine have been:synthesised. Two protons-can be removed by base fr om imides with electron-withdrawing ester substituents and free cyanof ormate esters are released from-the metal centre by substitution with dinitrogen or CO.