title: N-heterocyclic carbene ligands bearing hydrophilic and/or hydrophobic chains: Rh(I) and Pd(II) complexes and their catalytic activity.
abstract: A series of novel imidazolium salts bearing hydrophilic tetraethylene glycol (TEG) and/or hydrophobic long-chain alkyl (n-C12) functionalities, which are precursors for desired N-heterocyclic carbene (NHC) ligands, were synthesized and characterized. Rh(I)-NHC complexes were prepared in good yields by the silver carbene transfer method with NHC-Ag species derived from the imidazolium salts. The molecular structure of the Rh(I)-NHC complex having n-C12 chains has been determined by a single-crystal X-ray diffraction study and the complex is found to possess extended alkyl chains with anti conformations in the solid state. Hydrosilylation with the Rh(I) complexes and Suzuki-Miyaura coupling reactions with the Pd(II) complexes with these NHC ligands were carried out. In the latter case, the TEG moiety enhances catalytic activity considerably.
authors.affiliation: Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Kyoto, 615-8510, Japan.
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Ohta
authors.forename: Tetsuaki
authors.initials: T
authors.lastname: Fujihara
authors.forename: Yasushi
authors.initials: Y
authors.lastname: Tsuji