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 AsIII (two polymorphs), sbIII and BiIII 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 ASIII centres is defined by three asymmetrically chelating xanthate ligands. In contrast, the sbIIIand BiIII 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) �, β 90.18(2)�, 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) �; α 95.993(6), 95.99(3); β 100.92(1), 101.76(4); γ 99.04(1), 101.45(4)�; 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), Rw 0.034 (0.029, 0.052) for 2777 (2115, 1894) reflections.