Does an all-sulphur analogue of heptamolybdate exist?

The complexes [MoX₄]²⁻ (M = Mo; X = O or S) exist as the monomeric tetrahedral species in aqueous alkaline solutions. Acidification of tetraoxomolybdate results in the condensation of the tetrahedral units via a series of polyoxomolybdates leading to the ultimate formation of the trioxide MoO₃. Heptamolybdate [Mo₇O₂₄]⁶⁻ is the first major polyanion of the acidification reaction. In contrast, acidification of tetrathiomolybdates leads to the formation of amorphous molybdenum trisulphide via a dinuclear Mo(V) complex. The formation of the dinuclear Mo(V) complex precludes the formation of any higher nuclearity Mo(VI)-S complexes in aqueous solution. Thus it is shown that the all-sulphur analogue of heptamolybdate [M0₇S₂₄]⁶⁻ does not exist in alkaline medium and also cannot be isolated from aqueous acidic medium     

Synthesis, Characterization, and X-Ray Diffraction Analysis of Triethylenetetraammonium Tetrathiomolybdate

The reaction of gaseous H₂S with aqueous ammonium heptamolybdate in the presence of triethylenetetramine (trien) gave a red complex. The complex was recrystallized in hot water and characterized by element analysis and UV, visible, IR, and ¹H NMR spectroscopy. PMR has revealed accidental magnetic equivalence, resulting from the proximity of [MoS₄]^2- species in one complex molecule to the open triethylenetetramine ligand of another molecule. (TrienH₂)[MoS₄] crystallizes in the orthorhombic crystal system, space group Pca2₁, a=13.045(2), b=16.461(3), c=13.754(2) , =90, =90, =90°, V=2953.5(9) ³, Z=8, R₁=0.0323, wR₂=0.0730. The structure consists of the tetrahedral tetrathiomolybdate anions, forming an extended 3D framework in solids due to the interactions with triene cations via Mo-S...H-N hydrogen bonds.     

Preparation,Characterization, and X-Ray Structure Analysis of 1,4-Diazabicyclo-2,2,2-octane (DABCO) and Ammonium Cation with Tetrathiomolybdate Anion

The reaction of H₂S gas with an aqueous solution of ammonium heptamolybdate in the presence of 1,4-diazabicyclo-2,2,2-octane (DABCO) led to the formation of a red colored complex. The complex was recrystallized in hot water and characterized by elemental analysis and UV-Visible, FT-IR, and ¹H NMR spectroscopy. The single sharp peak in the ¹H NMR spectrum has revealed that all the methylene protons are equivalent due to the hydrogen resonating between the two nitrogens in the DABCO cation. The complex crystallizes in a cubic system with space group P2₁3, a = 10.9482(9) Å, α = 90°, V = 1325.3(7) ų, R ₃ = 0.0154, wR ₂ = 0.038, Z = 4. The structure consists of the tetrahedral tetrathiomolybdate anions, which form an extended three-dimensional network in the solid state involving Mo-S...H-N hydrogen bonding interactions with DABCO and the ammonium cation.Original Russian Text Copyright © 2004 by S. Pokhrel, K. S. Nagaraja, B. Varghese__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 945–949, September–October, 2004.     

Preparation, characterization, and X-ray structure analysis of diethylenetriammonium tetrathiomolybdate

The interaction of H₂S gas with aqueous ammonium heptamolybdate solution in the presence of diethylenetriamine (dien) led to the formation of diethylenetriammonium tetrathiomolybdate crystals. The elemental analyses, UV-Visible, IR, and ¹H NMR spectra suggested the presence of organic cation and (MoS₄)^2– moiety. The ¹H NMR revealed the presence of two sets of symmetrical A₂X₂ multiple patterns. The compound crystallizes in the monoclinic system with space group Pn, a = 7.196(6), b = 7.532(3), c = 11.525(10) Å, = 90°, = 90.17(3)°, = 90°, V = 624.78(8) ų, and Z = 2, wR ₁ = 0.0261 and wR ₂ = 0.0698. The structure consists of tetrahedral tetrathiomolybdate anions, which form an extended three-dimensional network in the solid state with Mo–SH–N hydrogen bonding with the organic cation.     

双核、三核钼硫原子簇状化合物的合成、反应和性质研究

本文提出了合成双核钼硫原子簇状化合物{[(n—Bu)_4N]_2[(S_2)OMo(μ—S)_2MoO(S_2)]和[(n—Bu)_4N]_2[(S_2)OMo(μ—S)_2MoS(S_2)]}以及三核钼硫原子簇状化合物(Ph_4P)_2[S_2Mo(μ—S)_2SMo(μ—S)_2MoS_2)的新方法,并进行了化学分析和红外光谱,电子光谱的测定。     

Synthesis and Crystal Structures of Four Novel Mo(W)/Cu/S Polymers Containing Thiolato Bridging Ligands

Four novel M/Cu/S polymers [Et₄N][MS₄Cu₃(S₂COEt)₂] (1a: M=Mo; 1b: M=W) and Et₄N][MS₄Cu₂SEt] (2a: M=Mo; 2b: M=W) have been prepared by reactions of [Et₄N]₂[MS₄] with CuS₂COEt and CuSEt. X-ray crystal structure determinations reveal that the polymeric anions of complexes 1a and 1b both consist of MS₄Cu₃ building blocks linked via bidentate [S₂COEt]⁻ bridging ligands to form 1D polymeric chains. The anion structures of the polymeric compounds 2a and 2b contain MS₄Cu₂ repeating units which are connected via μ-SEt⁻ ligands forming a zigzag chain running down the crystallographic b axis.     

原位分解法制备免预硫化CoMoS／γ-Al2O3催化剂的表征及加氢性能研究

以钼酸铵、硫代乙酰胺为原料合成四硫代钼酸铵溶液,γ-Al2O3为载体,首先浸渍Co盐,再负载四硫代钼酸铵,制备负载钴钼盐的前体.通过考察不同状态助剂钴对催化剂活性的影响,确定金属态存在的助剂钴可以显著提高催化剂的活性.对此前体采用原位分解法制备硫化态CoMoS/γ-Al2O3加氢精制催化剂,并进行XRD、XPS和HRTEM等表征.以FCC柴油为原料,考察了催化剂的活性及稳定性.结果表明,该催化剂的活性组分与载体γ-Al2O3的相互作用较弱,MoS2的分散度较好,堆积层数较高,大部分的MoS2以II型的CoMoS相存在,与传统方法制备的催化剂相比,硫化态的CoMoS/γ-Al2O3加氢精制催化剂具有更高的脱硫性能,1100 h稳定性试验结果表明该催化剂的稳定性较好.