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

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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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Supplementary files

Article information


Submitted
07 Jan 2020
Accepted
28 Jan 2020
First published
28 Jan 2020

Dalton Trans., 2020, Advance Article
Article type
Paper

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

D. E. Smith, V. K. Greenacre, A. L. Hector, R. Huang, W. Levason, G. Reid, F. Robinson and S. Thomas, Dalton Trans., 2020, Advance Article , DOI: 10.1039/D0DT00068J

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