AN 8-MEMBERED CYCLIC C,N-BIS(GERMADIYL)BIS(KETENIMINE)

The reaction of tert-butyllithium with (fluorodimesitylgermyl)- and (c hlorodimesitylgermyl)phenylacetonitrile (4a,b) leads to the lithium sa lts 5a (X = F) and 5b (X = Cl), which exhibit an ambident character: [ > C--C=N <----> > C=C=N-]Li+. Quenching of 5a with triphenylbromometha ne affords the germylketenimine 8, Mes(2)FGeC(Ph)=C=NCPh3. H-1 dynamic NMR spectroscopy allows the determination of the activation energy of the nitrogen inversion Delta G = 9.9 +/- 0.2 kcal/mol. In the absenc e of a trapping reagent, 5 undergoes an elimination of lithium halide with formation of the eight-membered cyclic C,N-bis(germadiyl) bis(ket enimine) 1, which is the first ring containing two ketenimine moieties . 1 has been characterized by IR (nu(C=C=N) 2015 cm(-1)) and C-13 NMR spectroscopy (170.87 ppm for the sp carbon) and by an X-ray structure determination, which displays a ''cyclohexane'' type structure in a ch air conformation.