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Switchable C ‐ and N ‐Bound Isomers of Transition‐Metal Cyanocarbanions: Synthesis and Interconversions of Cyclopentadienyl Ruthenium Complexes of Phenylsulfonylacetonitrile Anions
Author(s) -
Naota Takeshi,
Tannna Akio,
Kamuro Shigeaki,
Hieda Masayuki,
Ogata Kazuki,
Murahashi ShunIchi,
Takaya Hikaru
Publication year - 2008
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200701315
Subject(s) - cyclopentadienyl complex , isomerization , chemistry , moiety , ruthenium , intramolecular force , steric effects , ligand (biochemistry) , linkage isomerism , transition metal , stereochemistry , bond cleavage , metal , crystallography , photochemistry , medicinal chemistry , catalysis , organic chemistry , biochemistry , receptor
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)SO 2 Ph}(Cp)L 1 L 2 ] ( 3 ), and their N‐ bound isomers, [Ru + (Cp)(NCCH − SO 2 Ph)L 1 L 2 ] ( 4 ), were prepared by treating [RuCl(Cp)(PR 3 ) 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 α ‐ 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 CCN π‐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 μ 2 ‐ C , N coordination dimers [{Ru{CH(CN)SO 2 Ph}(Cp)(PPh 3 )} 2 ] ( 15 and 16 ).