title: Cyclobutadiene dianions consisting of heavier group 14 elements: synthesis and characterization.
abstract: The first "heavy" cyclobutadiene dianions (CBD2-), tetrakis(di-tert-butylmethylsilyl)-1,2-disila-3,4-digermacyclobutadiene dianion 22- and tetrakis(di-tert-butylmethylsilyl)tetrasilacyclobutadiene dianion 42-, have been synthesized by the reductive dehalogenation of the corresponding precursors with potassium graphite in THF. Structural characterization of [K+(thf)2]2.22- and [K+(thf)2]2.42- has been achieved by X-ray crystallography, showing that the central four-membered ring is significantly folded and has two eta2-1,3-coordinated potassium cations accommodated above and below the ring. The "heavy" CBD2-'s 22- and 42- were found to be nonaromatic compounds, a conclusion that was supported by nucleus-independent chemical shift (NICS) calculations showing a lack of diatropic ring current effects.
authors.affiliation: Department of Chemistry, University of Tsukuba, Tsukuba, Ibaraki 305-8571, Japan.
authors.forename: Vladimir Ya
authors.initials: VY
authors.lastname: Lee
authors.forename: Kazunori
authors.initials: K
authors.lastname: Takanashi
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