Crystal structures of tris(diethyldithiocarbamato)-antimony(III) and -bismuth(III)

The crystal structures of the title compounds, [Sb(S₂C·NEt₂)₃], (I), and [Bi(S₂C·NEt₂)₃] (II) have been determined from X-ray diffractometer data by the heavy-atom method and refined by least squares to R 0.07 (I), 3 [332 reflections] and 0.09 (II) [6 029 reflections]. Crystals of both are monoclinic, Z = 4, space group P2₁/a; (I): a = 14.665(5), b = 13.619(5), c = 12.642(4) Å, β = 99.86(4)°; (II): a = 14.825(4), b = 13.640(2), c = 12.605(3) Å, β = 100.01(3)°. (I) and (II) are isostructural; the symmetry of the M(S₂C)₃ unit resembles the C₃ symmetry of the arsenic derivative, with three short M-S bonds fac, one from each ligand [M-S 2.487(4)-2.631(4) (I); 2.595(5)-2.775(5) Å (II)], and three long bonds [M-S 2.886(4)-2.965(4) (I); 2.956(5)-2.964(4) Å (II)], with a considerable gap in the co-ordination about the pseudo-C₃ axis suggesting a stereochemically active lone-pair. The inversion image of the molecule approaches near this direction also, with a weak intermolecular metal-sulphur interaction [M ⋯ S^I, 3.389(4) (I), 3.210(4) Å (II)].