Thiochlorowolframate von Wolfram(V) und -(VI). Die Kristallstrukturen von PPh4[WSCl4] und (PPh4)2[WS2Cl4] � 2 CH2Cl2

Tungsten(VI) selenide tetrachloride, WSeCl4 - synthesis, properties, coordination complexes and application of [WSeCl4(SenBu2)] for CVD growth of WSe2 thin films

WSeCl₄ was obtained in good yield by heating WCl₆ and Sb₂Se₃in vacuo. Green crystals grown by sublimation were shown by single crystal X-ray structure analysis to contain square pyramidal monomers with apical WSe, and powder X-ray diffraction (PXRD) analysis confirmed this to be the only form present in the bulk sample. Density functional theory (DFT) calculations using the B3LYP-D3 functional replicated the structure, identified the key bonding orbitals, and were used to aid assignment of the IR spectrum of WSeCl₄. Reaction of WSeCl₄ with ligands L gave [WSeCl₄(L)] (L = MeCN, DMF, thf, py, OPPh₃, 2,2'-bipy, SeMe₂, SeⁿBu₂), whilst the dimers [(WSeCl₄)₂(μ-L-L)] were formed with L-L = Ph₂P(O)CH₂P(O)Ph₂, 1,4-dioxane and 4,4'-bipyridyl. The complexes were characterised by microanalysis, IR and ¹H NMR spectroscopy, and single crystal X-ray structures determined for [WSeCl₄(L)] (L = OPPh₃, MeCN, DMF) and [(WSeCl₄)₂(μ-L-L)] (L-L = 1,4-dioxane, 4,4'-bipyridyl). All except the 2,2'-bipy complex, which is probably seven-coordinate, contain six-coordinate tungsten with the neutral donor trans to WSe. Alkylphosphines, including PMe₃ and PEt₃, decompose WSeCl₄ upon contact, forming phosphine selenides (SePR₃). In contrast, the selenoether complexes [WSeCl₄(SeMe₂)] and [WSeCl₄(SeⁿBu₂)] were isolated and characterised. The crystal structure of the minor W(VI) by-product, [(WSeCl₄)₂(μ-SeMe₂)], was determined and using SMe₂, a few crystals of the W(V) species, [{WCl₃(SMe₂)}₂(μ-Se)(μ-Se₂)], were obtained and structurally characterised. The isolated W(VI) complexes are compared with those of WOCl₄ and WSCl₄ and the combination of experimental and computational data are consistent with WSeCl₄ being a weaker Lewis acid and its complexes significantly less stable than those of the lighter analogues, especially in solution. Low pressure chemical vapour deposition (LPCVD) using [WSeCl₄(SeⁿBu₂)] in the range 660-700 °C (0.1 mmHg) produced highly reflective thin films, which were identified to be WSe₂ by grazing incidence X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. XRD analysis of the thinner films revealed them to be highly oriented in the <00l> direction.

Tungsten disulfide thin films via electrodeposition from a single source precursor

We report a simple process for the electrodeposition of tungsten disulfide thin films from a CH₂Cl₂-based electrolyte using a tailored single source precursor, [NEt₄]₂[WS₂Cl₄]. This new precursor incorporates the 1 : 2 W : S ratio required for formation of WS₂, and eliminates the need for an additional proton source in the electrolyte to remove excess sulfide. The electrochemical behaviour of [NEt₄]₂[WS₂Cl₄] is studied by cyclic voltammetry and electrochemical quartz crystal microbalance techniques, and the WS₂ thin films are grown by potentiostatic electrodeposition.

Trithiotungsten(VI) complexes having phosphine-thiolate hybrid ligands: synthesis and cluster forming reactions with CuBr, FeCl(2), and [Fe(CH(3)CN)(6)](ClO(4))(2)

Five-coordinated trithiotungsten complexes (PPh(4))[(dmsp)W(S)(3)] (1a) and (PPh(4))[(dpsp)W(S)(3)] (1b) (R(2)PCH(2)CH(2)S(-); R = Me (dmsp-)), Ph (dpsp-))) were synthesized by addition of Hdmsp and Hdpsp to a THF solution of (PPh(4))[(EtS)W(S)(3)]. Treatment of 1a with CuBr in the presence of PPh(3) in CH(3)CN afforded a WCu(2) cluster (dmsp)WS(3)Cu(2)(PPh(3))(2)Br (2). The reaction of 1a with 1 equiv of FeCl(2) went smoothly to generate a 1:1 adduct (PPh(4))[(dmsp)WS(3)(FeCl(2))] (3), while 3 did not react further with excess FeCl(2). On the other hand, 3 was found to react with [Fe(CH(3)CN)(6)](ClO(4))(2), giving rise to an unusual tetranuclear cluster, [(dmsp)WS(3)](2)Fe(2)Cl (4), while the reaction of 1a with 2 equiv of [Fe(CH(3)CN)(6)](ClO(4))(2) led to a cyclic octanuclear cluster [(dmsp)WS(3)Fe](4) (5). Although the oxidation states of W(VI), Cu(I), and Fe(II) are retained in 2 and 3, reduction of the metal ions occurs in the formation of 4 and 5. All the complexes reported in this paper were structurally characterized by X-ray analysis. It is anticipated that the new type of trithiotungsten complexes, 1a and 1b, will serve as potential synthons for various heterometallic sulfide clusters.