Polysulfonylamine, LIV [1](12-Krone-4)lithiumdimesylamid-Acetonitril (3/2): Ein Kristall mit zwei prinzipiell unterschiedlichen Konformationen des gleichen Coronanden / Polysulfonylam ines, LIV [1] (12-Crown-4)lithium Dimesylamide-Acetonitrile (3/2): A Crystal with Two Fundamentally Different Conformations of the Same Coronand
Abstract [Li(12-crown-4){N(S02CH3)2}] is obtained from equimolar amounts of lithium dimesylamide and 12-crown-4 in methanol and crystallizes from acetonitrile as a 3/2 solvate. The crystallographic data of the latter at -130 °C are: monoclinic, space group P 2/n, a = 1053.4(3), b = 904.3(3), c = 2791.2(8) pm, β = 95.66(3)°, V = 2.646 nm3, Z = 6, Dx = 1.441 Mgm-3. Apart from CH3CN molecules residing in lattice cavities, the structure consists of two crystallographically independent [Li(12-crown-4){N(S02CH3)2}] ion pairs A and B in the ratio 2:1. In B, the Li and N atoms lie on a crystallographic twofold axis. In both ion pairs, Li is hexacoordinated by the four crown oxygen atoms O(C) and by one oxygen O(S) from each sulfonyl group of the anionic ligand. The coordination geometry of Li in A closely resembles that of CuII in the known structure of [Cu(12-crown-4)Cl2] and can be pictured as a distorted octahedron, where two cis sites are occupied by the O(S) atoms and the remaining vertices by the four oxygens of the macrocycle, which displays a [4 8] conformation. The lithium atom, the two O(S) and two O(C) atoms are arranged in an approximately square-planar pattern with L i-O (S) 203.6 and 205.1, Li-O(C) 206.9 and 219.1 pm, trans angles of 173.7 and 174.8°, and cis angles in the range 87.1 -93.6°. The angle between the remaining two Li -O(C) bonds with distances 214.7 and 221.5 pm is only 146.5° compared with 180° in an ideal octahedron. In ion pair B, the coronand assumes a [3 3 3 3] conformation close to C4 symmetry, as observ ed e. g. in the known structures of [Li(12-crown-4)NCS] with a square-pyramidal 0 4N-coordination and [Ca(12-crown-4)(H20)4]Cl2 · 4 H2O with a square-antiprismatic 0 8-geometry. The coordination polyhedron in B can be viewed as an incomplete cube in which two vertices related by a face diagonal are unoccupied. Important bond lengths and angles in B are: L i-O(S) 216.8, L i-O(C) 214.0 and 228.7pm; O(S) -L i-O (S) 82.0, O(C) -L i-O(C) 75.7/76.3 for adjacent and 120.4/121.9° for opposite ring oxygens.