FACILE C-N BOND-CLEAVAGE MEDIATED BY ELECTRON-RICH CYCLOPENTADIENYL COBALT(I) COMPLEXES

The reaction of [C5H5Co(PMe3)(2)] (1) with one equiv of CNCH2Ph leads to the formation of the substitution product [C5H5Co(CNCH2Ph)(PMe3)] ( 2) which even at room temperature undergoes an intramolecular oxidativ e addition to give the isomer [C5H5Co(CN)(CH2Ph)(PMe3)] (4). The corre sponding CpCo derivative [C5Me5Co(CN)(CH2Ph)(PMe3)] (8) is obtained f rom [C5Me5Co(PMe3)(2)] (5) and CNCH2Ph. In contrast to 2, the analogou s compound [C5H5Co(CNTol)(PMe3)] (6) is quite inert and does not react by N-C bond cleavage. The conversion of 2 to 4 in C6D6, acteone-d(6) and methanol-d(4) follows first order kinetics with a rate that is alm ost independent of the concentration of free PMe3. Both 2 and 6 react with Ph2CN2 to give the C,C-bound ketenimine complexes [C5H5Co(kappa(2 )-C,C-Ph2C=C=NR)(PMe3)] (9, 10) of which that with R = Tol rearranges thermally to the more stable N,C-bound isomer 11. (C) 1998 Elsevier Sc ience S.A. All rights reserved.