Thioether complexes of WSCl4, WOCl4 and WSCl3 and evaluation of thiochloride complexes as CVD precursors for WS2 thin films?

Dalton Transactions Pub Date: 2020-01-28 DOI: 10.1039/D0DT00068J

Abstract

The red-brown [(WSCl4)2{μ-RS(CH2)2SR}] (R = Me, Ph, iPr) and [(WSCl4)2{μ-MeS(CH2)3SMe}] have been made by reaction of WSCl4 with the thioether in a 2?:?1 molar ratio, in anhydrous CH2Cl2 solution, and characterised by microanalysis, IR, UV/Vis and 1H NMR spectroscopy. The X-ray structures of the four dithioether complexes reveal square pyramidal WSCl4 units and bridging dithioethers with W[double bond, length as m-dash]S trans to thioether sulfur. Paramagnetic W(V) complexes, [WSCl3{RS(CH2)2SR}] (R = Me, iPr), have been made similarly using a 1?:?≥1 ratio of reactants or longer reaction times. The W(VI) complexes, [WSCl4(SMe2)] and [WSCl4(SeMe2)], are also described. Analogous complexes of WOCl4, [(WOCl4)2{RS(CH2)2SR}] (R = Ph, iPr), have been made similarly from WOCl4, but reactions using MeS(CH2)nSMe (n = 2, 3) led to reduction to W(V), forming [WOCl3{MeS(CH2)nSMe], both of which were identified crystallographically. Curiously, they are geometric isomers: [WOCl3{MeS(CH2)3SMe}] has the dithioether trans Cl/Cl whereas in [WOCl3{MeS(CH2)2SMe}] it is trans O/Cl. Remarkably, low pressure chemical vapour deposition (CVD) experiments using the dinuclear W(VI) species, [(WSCl4)2{iPrS(CH2)2SiPr}], as a single source precursor produced thin films of 4H-WS2, identified by grazing incidence X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy; the tungsten thiochloride complex is the first single source low pressure CVD precursor for WS2. In contrast, the mononuclear W(V) complex, [WSCl3{iPrS(CH2)2SiPr}], does not deposit WS2 under similar conditions.

Graphical abstract: Thioether complexes of WSCl4, WOCl4 and WSCl3 and evaluation of thiochloride complexes as CVD precursors for WS2 thin films
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