An X-Ray Crystallographic Study of Tris(O-Methyl Dithiocarbonato)-Arsenic(III), Tris(O-Methyl Dithiocarbonato)-Antimony(III) and Tris(O-Methyl Dithiocarbonato)-Bismuth(III)

Abstract

The crystal structures of the methylxanthates of As^III (two polymorphs), sb^III and Bi^III are reported. In the monoclinic form of As(S₂COCH₃)₃ the molecular threefold symmetry, as found in the previously reported trigonal As(S₂COCH₃)₃, is not crystallographically imposed. The distorted octahedral environments about each of the AS^III centres is defined by three asymmetrically chelating xanthate ligands. In contrast, the sb^IIIand Bi^III analogues adopt different stereochemistries based on pseudo-m symmetry. In addition, the Sb (S₂COCH₃)₃ and Bi(S₂COCH₃)₃ molecules associate to form loosely held dimers , through weak intermolecular Me…S interactions, in their respective crystal lattices.

Crystals of β-As(S₂COCH₃)₃ are monoclinic, P2₁/c, with unit cell parameters a 14.816(4), b 9.641(6), c 21.255(6) Å, β 90.18(2)º, Z = 8. The antimony and bismuth compounds are isomorphous, crystallizing in the triclinic space group P1, with cell dimensions (bismuth details given second) a 5.904(1), 5.924(3); b 10.4891(8), 10.499(3); c 12.3635(9), 12.485(4) Å; α 95.993(6), 95.99(3); β 100.92(1), 101.76(4); γ 99.04(1), 101.45(4)º; Z = 2, 2.

The structures were solved by normal Fourier methods and refined by a full-matrix least-squares procedure in each case on reflections which satisfied the I ≥2.5σ(I) criterion. Final refinement details for the β arsenic (antimony, bismuth) compounds: R 0.034 (0.027, 0.055), R_w 0.034 (0.029, 0.052) for 2777 (2115, 1894) reflections.