| Abstract: | Trimethylsilyl Derivatives of Vb-Elements. II. Molecular and Crystal Structure of Tetrakis(trimethylsilyl)diarsine Pale yellow tetrakis(trimethylsilyl)diarsine 1 which is easily obtained from lithium bis(trimethylsilyl)arsenide · 2 tetrahydrofurane (THF) and 1,2-dibromoethane crystallizes in a trigonal, acentric space group. The dimensions of the unit cell determined at ?95 ± 5°C are: a = 974.2(2); c = 2 080.0(4) pm; Z = 3. Considering anomalous dispersion the refinement of structural data in space group P3121 converges at an R-value of 0.060, in its enantiomorph P3221, however, at 0.031. With a dihedral angle Si2′? As′? As? Si1 of ?125.7° the molecule adopts gauche conformation. Both bis(trimethylsilyl)arsino groups are symmetry-related by the crystallographic operation of the diad. Characteristic bond lengths and angles are: As? As 245.8(1); As? Si 236.5(1) and 236.2(2) pm; Si? As? Si 100.90(5); As? As? Si 93.87(3) and 113.63(4)°. The shortest intermolecular As? As distance is found to be 662 pm. |
