Preparation,crystal structure,and infrared characterization of the first thiocyanato-oxy-antimonate(III) [(CH3)4N]2[Sb6O4(NCS)12]

The salt (CH₃)₄N]₂Sb₆O₄(NCS)₁₂] is the first identified thiocyanato-oxy-antimonate(III) complex. Reported are details of the synthesis, relevant infrared data and its x-ray structure. The compound crystallizes in the triclinic space group P1 with Z = 2 (C₁₀H₁₂N₇O₂S₆Sb₃) and unit cell dimensions a = 11.314(6), b = 12.846(3), c = 8.679(2) Å; α = 91.93(3)°, β = 90.31(3)° and γ = 99.13(3)°. It contains centrosymmetric Sb₆O₄(NCS)₁₂]^2? anions packed with isolated tetramethyl-ammonium cations. The fundamental structural element of the anion is provided by the fusion of three SbOSbO rings forming a zig-zag portion of a ribbon, only slightly pleated. Peculiar is the unequivalence of the six thiocyanate ligands, though all primarily N-bonded to antimony atoms. Three thiocyanates are terminal while other three are asymmetrically N-bridging between two centers; two of this latter type are also interconnecting the anions via Sb???S contacts. There are three different antimony environments, the primary bonding at Sb being to one nitrogen and three oxygens, to one oxygen and three nitrogens and to two atoms of each type.