The chain-like polynuclear coordination compounds (ZnBr2)n(18-crown-6)2 (n = 4, 6, 8, 10) and [Zn5Br9][N(Tf2)]

Abstract

The chain-like polynuclear coordination compounds (ZnBr2)n(18-crown-6)2 (n = 4, 6, 8, 10) and [Zn5Br9][N(Tf)2] are obtained by reacting ZnBr2, SnBr4 and 18-crown-6 in the ionic liquid [(n-Bu)3MeN][N(Tf)2] (N(Tf)2: bis(trifluoromethylsulfonyl)imide). Structurally, chain-like anionic building units with corner- and edge-sharing ZnBr4/Zn(Br,O)4 tetrahedra of increasing lengths are obtained for (ZnBr2)n(18-crown-6)2. In contrast, [Zn5Br9][N(Tf)2] exhibits a cationic [Zn5Br9(18-crown-6)2](+) building unit with distorted tetrahedral, trigonal-bipyramidal and octahedral coordination of Zn(2+). Besides the coordination of Zn(2+) to Br(-), Zn(2+) is partially coordinated by 18-crown-6 with unusual folding of the crown-ether molecule. In sum, the polynuclear Zn-Br chains can be considered as intermediates between the finite [ZnBr4](2-) anion and the infinite solid ∞(3)[ZnBr2]. The addition of the Lewis-acid SnBr4 turned out to be essential for product formation and results in a Br(-) subtraction from ZnBr2. The coordination compounds are characterized based on structure analysis, thermogravimetry and energy-dispersive X-ray analysis.

The Bromine‐Rich Bromido Metallates [BMIm]2[SnBr6]·(Br2) and [MnBr(18‐crown‐6)]4[SnBr6]2·(Br2)4.5

“…Surprisingly, controlled Br 2 ‐release was observed from Zn 6 Br 12 (18‐crown‐6) 2 · (Br 2 ) 5 to Zn 4 Br 8 (18‐crown‐6) 2 · (Br 2 ) 3 and Zn 6 Br 12 (18‐crown‐6) 2 · (Br 2 ) 2 via crystal‐to‐crystal transformation with retention of the crystal shape (Figure b). In all reactions, the ionic liquid turned out as essential due to its weakly‐coordinating properties, its chemical stability, and due to the reduction of the vapour pressure of elemental bromine , , . Moreover, we observed that the presence of Lewis acids such as SnBr 4 is prerequisite for Br – subtraction from ZnBr 2 as the starting material , …”

“…In the system ZnBr 2 /Br 2 /(18‐crown‐6), we could identify a great number of coordination compounds (ZnBr 2 ) n (18‐crown‐6) 2 ( n = 4,6,8,10) that contain chain‐like anionic building units with corner‐ and edge‐sharing ZnBr 4 /Zn(Br,O) 4 tetrahedra of increasing lengths . Hereof, the hexanuclear ZnBr 4 tetrahedra chain in Zn 10 Br 20 (18‐crown‐6) 2 represents one of the largest discrete polynuclear metal‐halide chains described untill now (Figure a).…”

“…Compounds formed in the system ZnBr 2 /Br 2 /(18‐crown‐6):, (a) Coordination compounds (ZnBr 2 ) n (18‐crown‐6) 2 ( n = 4,6,8,10) with multinuclear ZnBr 4 ‐tetraedra chains of increasing lengths; (b). Bromine‐rich bromido zincate Zn 6 Br 12 (18‐crown‐6) 2 · (Br 2 ) 5 and decomposition to Zn 4 Br 8 (18‐crown‐6) 2 · (Br 2 ) 3 or Zn 6 Br 12 (18‐crown‐6) 2 · (Br 2 ) 2 via crystal‐to‐crystal transformation.…”

“…In the system ZnBr 2 /Br 2 /(18‐crown‐6), we could identify a great number of novel compounds, including the chain‐like coordination compounds (ZnBr 2 ) n (18‐crown‐6) 2 ( n = 4,6,8,10), that do not contain elemental bromine, as well as the bromine‐rich zinc bromides Zn 6 Br 12 (18‐crown‐6) 2 · (Br 2 ) 5 , Zn 4 Br 8 (18‐crown‐6) 2 · (Br 2 ) 3 , and Zn 6 Br 12 (18‐crown‐6) 2 · (Br 2 ) 2 . All these compounds were obtained from ionic‐liquid‐based synthesis of ZnBr 2 and 18‐crown‐6, in the presence or absence of elemental Br 2 .…”

Ionic‐Liquid‐Based Synthesis of the Bromine‐Rich Bromidoplatinates [NBu3Me]2[Pt2Br10](Br2)2 and [NBu3Me]2[Pt2Br10](Br2)3

“…We have frequently observed such effect related to the presence of strong Lewis acids such as SiBr 4 , SnBr 4 , or SnI 4 . [9,15] Although the respective species remain in solution subsequent to the reaction, the abstraction of Brby SiBr 4 and the resulting influence on the total stoichiometry -especially on the Br --to-Br 0 ratio of the reaction -can be rationalized as highly relevant. According to structure analysis based on single crystals, both title compounds crystallize in the monoclinic space group C2/c and exhibit very similar cell parameters ( Table 1) The [Pt 2 Br 10 ] 2anion is composed of two edge sharing PtBr 6 octahedra with Pt-Br distances ranging between 243.0(1) and 251.3(1) pm in 1 and 243.0(2) and 250.3(1) pm in 2 ( (Table 2).…”