摘要：

Structure and reactivity of C - and N -bound isomers of transition metal cyanocarbanions are described. A series of C -bound ruthenium phosphine complexes, RuCp [CH (CN) SO 2 Ph] L 2 and their N -bound isomers, Ru + Cp (NCCH - SO 2 Ph) L 2 have been synthesized by the reactions of RuCp-ClL 2 with the sodium salt of (phenylsulfonyl) acetonitrile and subsequent ligand exchange reactions. Structural characterization by X-ray diffraction indicated that carbanion moiety of the C -bound complexes has complete α-metalated structure, while that of the N -bound ones has zwitter ionic structure. Interconversions between C - and N -bound complexes have been observed upon heating, where relative stabilities of the C - and N -bound complexes are drastically changed depending mainly on the steric factors of ligands. The intra- and intermolecular mechanisms of the C - N interconversions were explored by means of kinetic studies and DFT calculations. The N -bound complexes have proven to show high catalytic activities for aldol and Michael reactions of nitriles. Kinetic studies revealed that the catalytic reaction proceeds via direct C-C bond formation of N -bound complexes and subsequent nitrile exchange reaction.

展开