Martha Poisot

Di­ammonium tetra­thio­tungstate(VI), (NH4)2[WS4], at 150 K

A low-temperature structure determination of the title compound, (NH4)2[WS4], indicates several short N—H⋯S contacts between the two crystallographically independent ammonium cations and the tetrahedral [WS4]2− anions, which are all located on crystallographic mirror planes.

Synthesis, Spectroscopic and X-Ray Structure Characterisation of Bis(tetramethylammonium) and Bis(tetra-n-butylammonium) Tetrathiomolybdates

The new tetraalkylammonium tetrathiomolybdates (Me4N)2[MoS4] (1) and (nBu4N)2[MoS4] (2) were prepared via a direct salt substitution using (NH4)2[MoS4] as starting material. Compound 1 crystallises in the non-centrosymmetric orthorhombic space group P212121 with a = 8.9233(4), b = 15.5210(9) and c = 37.255(3) Å. Compound 2 crystallises in the orthorhombic space group Fdd2 with a = 28.9142(18), b = 35.7811(10) and c = 15.6774(17) Å. The structures of both compounds consist of slightly distorted [MoS4]2− tetrahedra and tetraalkylammonium cations which are packed in different ways. Single crystals of (Et4N)2[MoS4] (3) were also investigated giving the lattice parameters a = 14.0346(7) and c = 12.5143(8) Å. A very strong disorder prevented a successful structure refinement and only the anion and one cation could be located. It is remarkable that the disorder of parts of the alkyl groups decreases with increasing chain length, in correlation with the IR and Raman vibrations of the [MoS4]2− tetrahedron showing a slight shift to lower energy with increasing alkyl chain length. The most prominent IR band of [MoS4]2− is broad but not split, indicating that the distortion of the tetrahedra is small.

Synthesis, crystal structures and properties of three new tetrathiomolybdates with organic ammonium cations

Abstract Three new tetrathiomolybdates (pipH2)[MoS4] (1), (trenH2)[MoS4]·H2O (2) and [(prop)4N]2- [MoS4] (3) (pip = piperazine, tren = tris(2-aminoethyl)amine and prop = n-propyl) were synthesized and characterized by elemental analysis, infrared spectroscopy, single crystal X-ray crystallography, and thermoanalysis. All compounds were prepared by the base promoted cation exchange method, i.e. by the reaction of the ammonium salt of [MoS4]2− with the corresponding organic amine or organic ammonium hydroxide. In the compounds 1 and 2 the organic amines pip and tren are diprotonated and they are linked to the tetrahedral [MoS4]2− dianions through weak hydrogen bonding interactions. The strength and number of these hydrogen bonds affect the Mo-S bond lengths and a relatively long Mo-S bond of 2.2114(8) Å is observed in 1 while the longest Mo-S bond in 2 is 2.1951(5) Å . In compound 3 no S···H-N interactions are possible and the Mo-S bond lengths scatter in a more narrow range compared to those in compounds 1 and 2. The thermal behavior was investigated using differential thermal analysis and thermogravimetry. On heating compound 1 decomposes in two closely related steps while 2 loses first the crystal water followed by the decomposition of the tetrathiomolybdate. The final products are amorphous molybdenum sulfides. The decomposition of compound 3 yields a very porous material with sponge-like morphology.

Synthesis, Spectroscopic and X-Ray Structure Characterisation of Bis(tetramethylammonium), Bis(tetraethylammonium) and Bis(tetrapropylammonium) Tetrathiotungstates

Abstract The three new tetraalkylammonium tetrathiotungstates ((Me)4N)2[WS4] (1), ((Et)4N)2[WS4] (2) and ((nPr)4N)2[WS4] (3) were prepared via a direct salt substitution using (NH4)2[WS4] as starting material. Compound 1 crystallises in the chiral orthorhombic space group P212121 with a = 8.9433(4), b = 15.5658(9) and c = 37.279(2) Å . Compound 2 crystallises in space group P21/n with lattice parameters a = 16.6695(12), b = 9.3415(6), c = 16.9965(13) Å and β = 117.185(15)°. The third compound 3 crystallises in space group C2/c with the lattice parameters a = 32.440(2), b = 13.8453(6), c = 15.0563(10) Å and β = 109.19(7)°. The structures of all compounds consist of slightly distorted [WS4]2− tetrahedra and tetraalkylammonium cations which are packed in different ways. One interesting observation is that the disorder of parts of the alkyl groups decreases with increasing chain length. The IR and Raman spectra show the vibrations of the [WS4]2− tetrahedron with a slight shift with increasing alkyl chain length. The most prominent IR-band of the [WS4]2− tetrahedra is broad but not split, indicating that the distortion of the tetrahedra is small.