title: Switchable C- and N-bound isomers of transition-metal cyanocarbanions: synthesis and interconversions of cyclopentadienyl ruthenium complexes of phenylsulfonylacetonitrile anions.
abstract: The synthesis, structure, and dynamic behavior of bistable C- and N-bound isomers of transition-metal cyanocarbanions are described. A series of C-bound cyclopentadienyl (Cp) ruthenium phosphane complexes, [Ru{CH(CN)SO2Ph}(Cp)L1L2] (3), and their N-bound isomers, [Ru+(Cp)(NCCH(-)SO2Ph)L1L2] (4), were prepared by treating [RuCl(Cp)(PR3)2] with the sodium salt of phenylsulfonylacetonitrile and performing ligand-exchange reactions with the resulting compounds. Structural characterization by X-ray diffraction indicates that the cyanocarbanion moiety of 3 has an alpha-metalated structure, whereas that of 4 has a zwitterionic, end-on structure. Heating these complexes in aprotic solvents gives rise to irreversible linkage isomerization between C- and N-bound isomers, in which the relative thermal stabilities vary greatly depending on the steric and electronic nature of the ligands. Mechanistic studies of N-to-C isomerization revealed that the reaction proceeds irreversibly in a unimolecular manner without the formation of coordinatively unsaturated species. A metal-sliding process, which occurs over the -C-C triple chemical bond N pi-conjugated surface of the cyanocarbanion moiety, was suggested by results from kinetic studies and density functional theory (DFT) calculations. C-to-N isomerizations proceed by the above-mentioned intramolecular process, with a temperature-dependent contribution from the formation and cleavage of mu2-C,N coordination dimers [{Ru{CH(CN)SO2Ph}(Cp)(PPh3)}2] (15 and 16).
authors.affiliation: Department of Chemistry, Graduate School of Engineering Science, Osaka University, Machikaneyama, Toyonaka, Osaka 560-8531, Japan. naota@chem.es.osaka-u.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Naota
authors.forename: Akio
authors.initials: A
authors.lastname: Tannna
authors.forename: Shigeaki
authors.initials: S
authors.lastname: Kamuro
authors.forename: Masayuki
authors.initials: M
authors.lastname: Hieda
authors.forename: Kazuki
authors.initials: K
authors.lastname: Ogata
authors.forename: Shun-Ichi
authors.initials: S
authors.lastname: Murahashi
authors.forename: Hikaru
authors.initials: H
authors.lastname: Takaya