title: Unexpected formation of Ru2Sn2 bicyclic four-membered ring complexes with butterfly and inverse-sandwich structures.
abstract: Reactions of tetraethyldilithiostannole 1 with [Cp*RuCl]4 afforded not η(5)-stannole dianion complexes but two novel bis(stannylene)-bridged dinuclear ruthenium complexes, which have butterfly and inverse-sandwich structures, respectively, depending on the stoichiometry of [Cp*RuCl]4 toward dilithiostannole. The redox behavior between the two complexes is found to be reversible. The molecular structures were determined by X-ray diffraction analysis. The Ru-Ru bond of the butterfly complex is 2.3428(6) Å, which is the shortest among those of dinuclear ruthenium complexes having Cp or Cp*Ru units. Theoretical calculations revealed that the very short Ru-Ru bond is due to the presence of one σ bond between the ruthenium atoms and two three-centered bonds delocalized over the two Ru2Sn rings.
authors.affiliation: Department of Chemistry, Graduate School of Science and Engineering, Saitama University, Shimo-okubo, Sakura-ku, Saitama City, Saitama 338-8570, Japan.
authors.forename: Takuya
authors.initials: T
authors.lastname: Kuwabara
authors.forename: Masaichi
authors.initials: M
authors.lastname: Saito
authors.forename: Jing-Dong
authors.initials: JD
authors.lastname: Guo
authors.forename: Shigeru
authors.initials: S
authors.lastname: Nagase