title: Tetrasilacyclobutadiene ((t)Bu(2)MeSi)(4)Si(4): a new ligand for transition-metal complexes.
abstract: The anionic complex of [tetrakis(di-tert-butylmethylsilyl) tetrasilacyclobutadiene]dicarbonylcobalt, [(R4Si4)Co(CO)2]-.K+ (R = SiMetBu2) 2-.K+, was synthesized by the reaction of tetrasilacyclobutadiene dianion dipotassium salt [R4Si4]2-.2K+ 1 with an excess of CpCo(CO)2 in THF. X-ray analysis of 2-.[K+(diglyme)2(THF)] showed an almost planar Si4 ring of rectangular shape with an in-plane arrangement of the silyl substituents. 2- was also prepared as a free anion with the [K+[2.2.2]cryptand] counterion by complexation with [2.2.2]cryptand and as a dimer {2-.[K+(THF)3]}2 without complexing reagents in THF. Such a tetrasilacyclobutadiene fragment represents a new type of ligand for Co complexes, being the first example of a cyclobutadiene containing only heavier group 14 elements.
authors.affiliation: Department of Chemistry, Graduate School of Pure and Applied Sciences, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Kazunori
authors.initials: K
authors.lastname: Takanashi
authors.forename: Vladimir Ya
authors.initials: VY
authors.lastname: Lee
authors.forename: Tadahiro
authors.initials: T
authors.lastname: Matsuno
authors.forename: Masaaki
authors.initials: M
authors.lastname: Ichinohe
authors.forename: Akira
authors.initials: A
authors.lastname: Sekiguchi