The crystal and molecular structure of O-ethylxanthato-bis(quinolin-8-olato)antimony(III) and a redetermination for tris(O-ethylxanthato)antimony(III)

The crystal structures of the title compounds Sb(C₉H₆NO)₂(S₂COC₂H₅) (1) and Sb(S₂COC₂H₅)₃ (2) have been determined by three dimensional X-ray diffraction techniques and refined by a least squares method; final R 0.049 for 2911 reflections I ? 3σ(I)] for (1) and R 0.047, R_w 0.046 for 846 reflections I ? 2σ(I)] for (2). Crystals of (1) are triclinic, space group P1, a = 10.825(2), b = 11.131(2), c = 8.911(1) Å, α = 109.45(1), β = 95.92(1) and γ = 93.02(1)° with Z = 2. Crystals of (2) are rhombohedral, space group R$\text{3}$, a_rhomb = 10.138(3) Å and α = 103.43(2)°. The environment of the Sb atom in (1) is based on a pentagonal bipyramidal geometry consisting of the six donor atoms of the three chelating ligands and a stereochemically active lone-pair of electrons which occupies the remaining axial position. The xanthate ligand chelates the Sb atom almost symmetrically with two long SbS bonds of 3.059(2) and 3.171(2) Å. In contrast the xanthate ligands in (2) chelate the Sb atom with asymmetric SbS bonds of 2.511(2) and 3.002(3) Å.