title: [Sb10Se10]2+, a heteronuclear polycyclic polycation from a room-temperature ionic liquid.
abstract: Reaction of antimony, selenium, and selenium(IV) chloride in the Lewis acidic ionic liquid [BMIM]Cl/AlCl(3) (BMIM: 1-n-butyl-3-methylimidazolium) at room temperature yielded air-sensitive black block-shaped crystals of [Sb(10)Se(10)][AlCl(4)](2). The triclinic unit cell (space group P1, a=947.85(2), b=957.79(2), c=1166.31(3) pm; α=103.622(1), β=110.318(1), γ=99.868(1)°; Z=1) contains the first mixed antimony/selenium polycation, [Sb(10)Se(10)](2+). The centrosymmetric polycyclic cation consists of two realgar-like [Sb(4)Se(4)] cages, which are connected through positively charged, three-bonded selenium atoms with a central [Sb(2)Se(2)] ring. Quantum chemical calculations predict semiconducting behavior of the compound and indicate primarily covalent bonding with varying ionic contribution within the [Sb(10)Se(10)](2+) polycation, while the interactions between the polycation and the [AlCl(4)](-) anions are predominantly ionic. The applicability of the Zintl concept to the chemical bonding in the heteronuclear polycation was evaluated by a thorough quantum chemical analysis.
authors.affiliation: Department of Chemistry and Food Chemistry, Technische Universität Dresden, Dresden, Germany.
authors.forename: Ejaz
authors.initials: E
authors.lastname: Ahmed
authors.forename: Anna
authors.initials: A
authors.lastname: Isaeva
authors.forename: Andy
authors.initials: A
authors.lastname: Fiedler
authors.forename: Marcel
authors.initials: M
authors.lastname: Haft
authors.forename: Michael
authors.initials: M
authors.lastname: Ruck