title: Formation and coordination modes of the C4E4 moiety (E = COOMe) bound to two palladium(II) moieties.
abstract: The transmetallation of the palladacyclopentadiene complex Pd{C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy) with the dicationic Pd(II) complex [Pd(bipy)(CH(3)CN)(2)][BF(4)](2) afforded a terminally σ-palladated diene complex [Pd(2){μ-η(1):η(1)-C(COOMe)C(COOMe)C(COOMe)C(COOMe)}(bipy)(2)(CH(3)CN)(2)][BF(4)](2). It was revealed by X-ray crystallographic analysis that replacement of the acetonitrile ligands in a terminally σ-palladated diene complex with PPh(3) ligands resulted in the conformation change of the σ-palladated diene moiety from skewed s-cis to planar s-trans. Treatment of a bis-triphenylphosphine dipalladium complex [Pd(2)(PPh(3))(2)(CH(3)CN)(4)][PF(6)](2) with dimethoxyacetylene dicarboxylate (DMAD) (1 equiv.) in acetonitrile resulted in the insertion of DMAD to the Pd-Pd bond to afford [Pd(2){μ-η(1):η(1)-C(COOMe)C(COOMe)}(PPh(3))(2)(CH(3)CN)(4)][PF(6)](2). Addition of the second DMAD gave the ylide-type complex [Pd(2){μ-η(2):η(3)-C(COOMe)C(COOMe)C(COOMe)C(COOMe)(PPh(3))}(PPh(3))(2)(CH(3)CN)(3)][PF(6)](2) of which the structure was determined by X-ray crystallographic analysis.
authors.affiliation: Department of Applied Chemistry, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan. tetsu@chem.eng.osaka-u.ac.jp
authors.forename: Tetsuro
authors.initials: T
authors.lastname: Murahashi
authors.forename: Taketoshi
authors.initials: T
authors.lastname: Okuno
authors.forename: Kentaro
authors.initials: K
authors.lastname: Usui
authors.forename: Kohei
authors.initials: K
authors.lastname: Takase
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Otani
authors.forename: Sensuke
authors.initials: S
authors.lastname: Ogoshi
authors.forename: Hideo
authors.initials: H
authors.lastname: Kurosawa