Controlled Synthesis of Pnicogen–Chalcogen Polycations in Ionic Li­quids

Abstract

Three new pnicogen–chalcogen polycations were synthesized under specific conditions in the Lewis‐acidic ionic liquids (ILs) [EMIm]X·nAlX3 and [BMIm]X·nAlX3 (X = Cl, Br; [EMIm]: 1‐ethyl‐3‐methylimidazolium, [BMIm]: 1‐butyl‐3‐methylimidazolium) and crystallized as their tetrahalogenidoaluminate salts. Single‐crystal X‐ray diffraction revealed the new polycation [Bi6Te4Br2]4+ in triclinic [Bi6Te4Br2](AlBr4)4 as the reaction product of bismuth, tellurium, and bismuth tribromide. Substitution of the elements with Bi2Te3 yielded the heterocubane [Bi4Te4]4+ in tetragonal [Bi4Te4](AlBr4)4, which crystallizes isotypically to its known chlorine counterpart. The latter is also accessible from ILs. The interactions between cations and anions were evaluated by quantum‐chemical calculations. Bi2S3, which is insoluble in most media, readily dissolves in the employed IL and forms the new augmented heterocubane [Bi3S4AlCl]3+, which crystallizes with the complex anion [S(AlCl3)3]2– as triclinic [Bi3S4AlCl][S(AlCl3)3]AlCl4. Quantum‐chemical calculations support the assignment of elements in this compound. The monoclinic crystal structure of [Sb13Se16](AlCl4)6(Al2Cl7) contains a new member of the small family of pnicogen–chalcogen spiro‐heterocubanes.

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.…”

“…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]. Thereby, [Sb 13 Se 16 ][AlCl 4 ] 6 Al 2 Cl 7 can be interpreted as intermediate during the decomposition of [Sb 2 Se 2 ][AlCl 4 ] into Sb 2 Se 3 .…”

“…In chloride-free [BMIm]Br·4.1AlBr 3 , either the cube-shaped polycation [Bi 4 Te 4 ] 4+ or the realgar-like [Bi 6 Te 4 Br 2 ] 4+ forms at 100 °C depending on the employed starting materials [30]. If bismuth telluride and bismuth tribromide are reacted, [Bi 4 Te 4 ][AlBr 4 ] 4 crystallizes as the sole polycation phase.…”

“…If bismuth telluride and bismuth tribromide are reacted, [Bi 4 Te 4 ][AlBr 4 ] 4 crystallizes as the sole polycation phase. Without addition of bismuth bromide, Bi 2 Te 3 shows only low solubility in the employed IL and no formation of a solid product has been observed [30]. The reaction of bismuth, tellurium, and bismuth tribromide under the same conditions, however, leads to the crystallization of [Bi 6 Te 4 Br 2 ][AlBr 4 ] 4 .…”

“…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.…”