title: Coordination chemistry of highly hemilabile bidentate sulfoxide N-heterocyclic carbenes with palladium(II).
abstract: Imidazolium salts, [RS(O)-CH2 (C3 H3 N2 )Mes]Cl (R=Me (L1a), Ph (L1b)); Mes=mesityl), make convenient carbene precursors. Palladation of L1a affords the monodentate dinuclear complex, [(PdCl2 {MeS(O)CH2 (C3 H2 N2 )Mes})2 ] (2a), which is converted into trans-[PdCl2 (NHC)2] (trans-4a; N-heterocyclic carbene) with two rotamers in anti and syn configurations. Complex trans-4a can isomerize into cis-4a(anti) at reflux in acetonitrile. Abstraction of chlorides from 4a or 4b leads to the formation of a new dication: trans-[Pd{RS(O)CH2(C3H2N2)Mes}2](PF6)2 (R=Me (5a), Ph (5b)). The X-ray structure of 5a provides evidence that the two bidentate SO-NHC ligands at palladium(II) are in square-planar geometry. Two sulfoxides are sulfur- and oxygen-bound, and constitute five- and six-membered chelate rings with the metal center, respectively. In acetonitrile, complexes 5a or 5b spontaneously transform into cis-[Pd(NHC)2(NCMe)2](PF6)2. Similar studies of thioether-NHCs have also been examined for comparison. The results indicate that sulfoxides are more labile than thioethers.
authors.affiliation: Department of Chemistry, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei, 10617 Taiwan (R.O.C.), Fax: (+886) 2-2363-6359.
authors.forename: Kuo-Hsuan
authors.initials: KH
authors.lastname: Yu
authors.forename: Chia-Ching
authors.initials: CC
authors.lastname: Wang
authors.forename: I-Hsin
authors.initials: IH
authors.lastname: Chang
authors.forename: Yi-Hung
authors.initials: YH
authors.lastname: Liu
authors.forename: Yu
authors.initials: Y
authors.lastname: Wang
authors.forename: Cornelis J
authors.initials: CJ
authors.lastname: Elsevier
authors.forename: Shiuh-Tzung
authors.initials: ST
authors.lastname: Liu
authors.forename: Jwu-Ting
authors.initials: JT
authors.lastname: Chen
keywords: carbenes; coordination modes; palladium; structure elucidation; sulfur