Tetrakis(tetrahydrofuran-0)calcium- und -strontium-bis[bis(trimethylsilyl)- arsanid] - Vergleich der spektroskopischen Parameter sowie der Molekülstrukturen Tetrakis(tetrahydrofuran-0)calcium and Strontium Bis[bis(trimethylsilyl)- arsanide] - A Comparison of the Spectroscopic Parameters and the Molecular Structures

Calciumand strontium bis[bis(trimethylsilyl)amide] react with bis(trimethylsilyl)arsane in tetrahydrofuran to give the corresponding tetrakis(tetrahydrofuran-O) metal bis[bis(trimethylsilyl)arsanides]. The calcium derivative crystallizes in the triclinic space group P I with a = 1191.7(2), b = 1232.0(2), c = 1655.0(2) pm, a = 102.46(1)°, ß = 107.92(1)°, y = 104.66(1)° and Z = 2, the strontium derivative in the orthorhombic space group Pbca with a = 2153.4(3), b = 1852.2(3), c 2182.4(3) pm and Z = 8. Both molecules exist as frans-isomers with a nearly linear A s -M -A s moiety; however, the strontium analogue contains two remarkably different configurations for the arsenic atoms. One As atom is surrounded nearly trigonally planar with a S r -A s bond length of 310 pm, whereas the other pnictogen atom has an angle sum of 338° with a S r -A s distance of 315 pm.