T. Peppel, M. Köckerling
Dec 1, 2009
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Zeitschrift für Kristallographie - New Crystal Structures
Abstract
C4H3Br3N2, triclinic, P1 (no. 2), a = 6.9066(3) Å, b = 7.0812(3) Å, c = 16.1046(6) Å, α = 78.093(2)°, β = 82.467(2)°, γ = 89.781(2)°, V = 763.8 Å, Z = 4, Rgt(F) = 0.026, wRref(F) = 0.064, T = 173 K. Source of material 1-Methyl-1H-imidazole (24.6 g, 0.3 mol) and sodium acetate trihydrate (100 g, 0.7 mol) were dissolved in 350 ml glacial acetic acid and a solution of bromine (143.6 g, 0.9 mol) in 50 ml of glacial acetic acid was added slowly under cooling. The resulting solution was stirred overnight and then poured onto 500 ml of ice water. The precipitate of 2,4,5-tribromo-1-methyl-1H-imidazole was filtered off and recrystallized from aqueous ethanol. Yield: 50.0 g (52 %), mp. 93 °C. Discussion Already in the late 19th century Wyss and Wallach reported the correct molecular formula of 2,4,5-tribromo-1-methyl-1Himidazole and they discussed possible chemical structures [1,2]. Until now there has been no X-ray determination of the crystal structure of this compound. The imidazole core is a key for a huge variety of important biologically active substances. It has found many applications in metalcarbene catalysts and is most important in ionic liquids (ILs) and magnetic ILs [3-8]. Polybrominated imidazole building blocks are useful as starting materials in the synthesis of very dense halogenated ILs [9]. The title compound crystallizes with two symmetry independent molecules in the asymmetric unit. The orientation of the molecules gives short hydrogen-bonding contacts between Br atoms and methyl groups of neighbouring units. The figure shows such an intermolecular hydrogen-bonding contact as thermal ellipsoid plot at the 50 % probability level. Z. Kristallogr. NCS 224 (2009) 597-598 / DOI 10.1524/ncrs.2009.0262 597 © by Oldenbourg Wissenschaftsverlag, München Crystal: colorless plate, size 0.20 × 0.30 × 0.45 mm Wavelength: Mo Kα radiation (0.71073 Å) .: 157.56 cm−1 Diffractometer, scan mode: Bruker-Nonius X8 APEX CCD, #/% 2,max: 52.88° N(hkl)measured, N(hkl)unique: 10213, 3016 Criterion for Iobs, N(hkl)gt: Iobs > 2 )(Iobs), 2684 N(param)refined: 164 Program: SHELXTL [10] Table 1. Data collection and handling. H(4A) 2i 0.1751 0.5805 0.664 0.035 H(4B) 2i 0.0842 0.7679 0.6105 0.035 H(4C) 2i 0.3129 0.7635 0.6182 0.035 H(8A) 2i 0.2722 −0.3101 1.1183 0.046 H(8B) 2i 0.4013 −0.1602 1.0439 0.046 H(8C) 2i 0.4029 −0.3857 1.0427 0.046 Table 2. Atomic coordinates and displacement parameters (in Å). Atom Site x y z Uiso