The crystal and molecular structure of triphenyltelluronium thiocyanate, (C6H5)3Te(NCS), has been determined from three-dimensional x-ray data collected by counter techniques. The structure was refined by full-matrix least-squares methods.
The refinement was carried out using 5543 nonzero reflections for which F > o(F) and assuming anisotropic thermal motion for all nonhydrogen atoms. The least-squares refinement led to a final value of the conventional R factor (on F) of 0.039. Crystal data are as follows: space group Pi; a = 13.339 (12), b = 13.885 (lo), c = 14.796 (11) A; a = 82.53 (6), p = 76.53 (7), y = 78.20 (7)' (23 'C); V = 2599 A'. Triphenyltelluronium thiocyanate is bioligomeric in the solid state. The unit cell (2 = 6) consists of one dimer and one tetramer separated by van der Waals distances. The oligomers are predominantly ionic with tellurium-nitrogen and tellurium-sulfur distances significantly shorter than respective van der Waals distances.
Te-N distances range from 2.963 (8) to 3.182 (8) A; the TeS distances range from 3.256 (4) to 3.616 (4) A. Both end-to-end and terminally bridging NCS groups are present. The central eight-membered ring of the dimer is puckered and has a chair configuration with a dihedral angle of 93.2'. The overall configuration of the tetramer is that of a step with a dihedral angle of 99.9'. Five- and six-coordinate tellurium atoms are present in distorted square-pyramidal and distorted octahedral geometries, respectively. The three crystallographically independent criphenyltelluronium cations have a trigonal-pyramidal shape but possess no symmetry, due to the conformation adopted by the phenyl rings. The mean Te-C distance is 2.13 (2) 8, and the mean C-Te-C angle is 97.3 (6)'. The thiocyanate groups are ionic with mean N-C and C-S distances of 1.15 (2) and 1.64 (1) A, respectively.