Structural systematics in antimony tris(xanthates): Sb(S₂COR)₃

Abstract

Crystallography shows the hexagonal form of Sb(S₂COEt)₃ to have three-fold symmetry in which the antimony atom is chelated by asymmetrically coordinating xanthate ligands, Sb—S = 2.5204(8) and 3.0603(11) Å. The lone pair of electrons projects out of the triangular face defined by the three weakly coordinating sulfur atoms. The crystal structure comprises layers that stack in an ... ABAB ... fashion in contrast to the previously determined trigonal form. A similar coordination geometry is found in the structure of Sb(S₂CO—nPr)₃. Molecules aggregate into a supramolecular helical chain via secondary Sb ... S interactions. Crystal data for C₉H₁₅O₃S₆Sb, hexagonal, P6₃, a = 14.642(4), c = 4.6674(10) Å, V = 866.6(4) ų, Z = 2, R = 0.021; C₁₂H₂₁O₃S₆Sb, monoclinic, P2₁/c, a = 14.671(5), b = 8.898(3), c = 17.185(6) Åb = 111.288(4)°, V = 2090.3(12) ų, Z = 4, R = 0.042. An analysis of all available Sb(S₂COR)₃ structures shows the adoption of molecules with C₃ or C_s symmetry. In the case of the latter, well defined intermolecular Sb ... S contacts lead to supramolecular double chains. For the structures with C₃ symmetry, supramolecular aggregation patterns are more varied and less dependent on Sb ... S contacts.