[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.

Controlled Synthesis of Polyions of Heavy Main-Group Elements in Ionic Liquids

“…In recent years, we synthesized several binary or ternary antimony-selenium heteropolycations (Figure 6) in Lewis-acidic ILs [BMIm] X · n Al X 3 ( X = Cl, Br; n = 1.2–5.2) [30,34,35,38]. Thereby, we deduced two main decisive reaction parameters for the controlled synthesis of a desired polycation in this system: temperature and the utilization of different auxiliaries.…”

“…If SeCl 4 is added to Sb and Se in [BMIm]Cl· n AlCl 3 , [Sb 10 Se 10 ][AlCl 4 ] 2 can be accessed at room temperature [35]. However, if SeCl 4 is omitted, either the catena- compound [Sb 2 Se 2 ][AlCl 4 ] or the cluster compound [Sb 13 Se 16 ][AlCl 4 ] 6 Al 2 Cl 7 form depending on the reaction temperature [30,34].…”

“…Owing to the distinctive physicochemical properties of ILs (wide liquidus range, high redox and thermal stability, negligible vapor pressure, and tunable polarity) and their advantages over organic solvents, classic melts, or solid state reactions, their applications include separation techniques [7,8,9], lubrication [10], electrodeposition [11], acting as electrolytes in photovoltaic devices (e.g., solar cells) [12,13,14], catalysis for clean technology [15,16,17,18], polymerization processes [19], crystal engineering of a wide range of inorganic substances [20,21,22,23,24,25], and syntheses of new inorganic materials in general [23,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,42,43,44,45,46,47,48,49,50,51]. Recently, several comprehensive reviews on syntheses of inorganic compounds in ILs have been published by Taubert [52], Feldmann [28], Dehnen [51], Janiak [42,53], Scrosati and Passerini [48], Morris [54], Mudring [55], Prechtl [56], Zhu [57], Dai [58], and Ruck [23,27,59] among others.…”

Reprint of “Coordination chemistry of homoatomic ligands of bismuth, selenium and tellurium”

“…So-called spherical aromaticity [58] is responsible for a nuclear independent chemical shift (NICS) in the NMR spectra and an additional diamagnetic contribution in the susceptibility of the respective compounds. A rather different bonding situation accounts for heteronuclear polyhedral polycations of bismuth or antimony with tellurium or selenium [59][60][61][62][63]. Here electron counting is based on 2c2e bonds similar to Zintl phases, although interatomic distances as well as DFT calculations suggest that in particular linear three-centre bonds also occur.…”

[SbCl2(η2-1,4-dt)(μ2-1,4-dt)][AlCl4]: Ionic Liquid-based Synthesis of a Stibenium Cation (dt = dithiane)

“…Lewisacidic ionic liquids are known as suitable reaction media for the synthesis of inorganic compounds exhibiting novel structural building units and bonding situations [7]. This also includes cases of elementelement bonding and low oxidation states of the main-group elements.…”