title: 1,3-Diphosphacyclobutane-2,4-diyl-2-ylidenide: A Unique Carbene and Its Trimethylalane Complex.
abstract: A unique bonding situation is displayed by the lithium 1,3-diphosphacyclobutane-2,4-diyl-2-ylidenide 2 small middle dot[Li(thf)(n)](+) (Ar=2,4,6-tBu(3)C(6)H(2)) obtained by deprotonation of 1. According to ab initio calculations, the anion 2 can viewed as a cyclic bis(phosphanyl)carbene. Reaction with trimethylaluminum gives the complex 3 small middle dot[Li(thf)(4)](+), whose crystal structure is presented.
authors.affiliation: Institut für Anorganische Chemie der Universität, Gerhard-Domagk-Strasse 1, D-53121 Bonn (Germany).
authors.initials: E
authors.lastname: Niecke
authors.initials: A
authors.lastname: Fuchs
authors.initials: M
authors.lastname: Nieger
authors.initials: O
authors.lastname: Schmidt
authors.initials: WW
authors.lastname: Schoeller