BIS[TRIS(TRIMETHYLSILYL)SILYL] ZINC, CADM IUM, AND MERCURY - A STRUCTURAL STUDY BY IR AND RAMAN-SPECTROSCOPY AND X-RAY ANALYSES

Raman and FT-IR spectra of bis [tris(trimethylsilyl)silyl] zinc (1), c admium (2) and mercury (3) were recorded. The vibrational data are in agreement with either D-3h or a D-3d symmetry. The latter had been sho wn to be the correct one at least for the solid state by X-ray diffrac tion experiments. All three compounds crystallize isomorphically in th e triclinic centrosymmetric space group P1. [2 (T = 293 K): a = 9.4388 (11); b = 9.744(2); c = 12.926(2); alpha = 68.200(12); beta = 71.971(1 0); gamma = 60.925(10); Z = 1; (T = 173 K): a = 9.336(6); b = 9.585(5) ; c = 12.488(8); alpha = 68.77(4); beta = 72.28(4); gamma = 62.06(4); 3: a = 9.467(2); b = 9.749(2); c = 12.885(2); alpha = 67.840(14); beta = 71.510(14); gamma = 60.890(14); Z = 1]. The Hg-Si bondlength in 3 w as found to be 246.9(2) pm, somewhat shorter then in all disilylmercur y derivatives investigated so far and even shorter than the Cd-Si bond in 2 (250.4(1)pm). Bondlengths and angles within the tris(trimethylsi lyl)silyl group are virtually equal in all three group 12 derivatives and lie in the expected range.