Solvothermal Synthesis, Crystal Structure, and Thermoanalytical Investigations of the New Layered Thioantimonate(III) [Fe(C4H13N3)2]Sb6S10 · 0.5 H2O

The novel thioantimonate(III) [Fe(C4H13N3)2]Sb6S10 · 0.5 H2O was synthesised under mild hydrothermal conditions by allowing elemental Fe, Sb, and S to react in a 50% diethylenetriamine (dien) solution. The compound crystallises in the monoclinic space group C2/c with a = 33.789(3), b = 8.5697(4), c = 24.620(2) Å, β = 118.411(8)°, and V = 6270.3(7) Å3. In the crystal structure, five SbS3 trigonal pyramids and one SbS4 unit are interconnected by sharing common S atoms, forming Sb2S2, Sb4S4, and Sb5S5 heterocycles. The layered [Sb6S10]2− anion is formed by condensation of the rings in the order Sb4S4−Sb5S5−Sb2S2−Sb5S5−Sb4S4. The interconnection of the different SbxSx heterocycles leads to the formation of a large Sb16S16 ring. The special geometries of the SbSx units and their interconnection results in a new and unprecedented architecture of the four-atoms thick thioantimonate layer. The calculated bond valence sums (BVS) for the Sb atoms range from 3.07 to 3.16 v. u., indicating that the Sb atoms are formally trivalent. The [Fe(dien)2]2+ cations and the water molecule are located between neighbouring layers. The thermal behaviour of the compound was investigated using DTA-TG measurements. Upon heating decomposition starts at about 200 °C, which is accompanied by the removal of the organic ligands and the incorporated water molecules. In the X-ray powder pattern of the decomposition product, the three compounds Sb2S3, FeSb2S4, and FeS could be identified.