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

Tungsten(VI) selenide tetrachloride, WSeCl4 - synthesis, properties, coordination complexes and application of [WSeCl4(SenBu2)] for CVD growth of WSe2 thin films
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 Sb2Se3 in 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.
0300-9246
2400-2412
Greenacre, Victoria
c665a38b-0b1a-4671-ac75-bf0679dd1c57
Hector, Andrew L.
f19a8f31-b37f-4474-b32a-b7cf05b9f0e5
Huang, Ruomeng
c6187811-ef2f-4437-8333-595c0d6ac978
Levason, William
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Sethi, Vikesh
e0c3adf8-b928-46c4-b59f-4428cafe7774
Reid, Gillian
37d35b11-40ce-48c5-a68e-f6ce04cd4037
Greenacre, Victoria
c665a38b-0b1a-4671-ac75-bf0679dd1c57
Hector, Andrew L.
f19a8f31-b37f-4474-b32a-b7cf05b9f0e5
Huang, Ruomeng
c6187811-ef2f-4437-8333-595c0d6ac978
Levason, William
e7f6d7c7-643c-49f5-8b57-0ebbe1bb52cd
Sethi, Vikesh
e0c3adf8-b928-46c4-b59f-4428cafe7774
Reid, Gillian
37d35b11-40ce-48c5-a68e-f6ce04cd4037

Greenacre, Victoria, Hector, Andrew L., Huang, Ruomeng, Levason, William, Sethi, Vikesh and Reid, Gillian (2022) Tungsten(VI) selenide tetrachloride, WSeCl4 - synthesis, properties, coordination complexes and application of [WSeCl4(SenBu2)] for CVD growth of WSe2 thin films. Dalton Transactions, 51 (6), 2400-2412. (doi:10.1039/D1DT03980F).

Record type: Article

Abstract

WSeCl4 was obtained in good yield by heating WCl6 and Sb2Se3 in 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.

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WSeCl4 Dalton 23_11_2021 final revised 04_01_22 clean copy - fig numbers corrected - Accepted Manuscript
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WSeCl4-ESI 23_11_2021 master final
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Accepted/In Press date: 7 January 2022
e-pub ahead of print date: 11 January 2022

Identifiers

Local EPrints ID: 454507
URI: http://eprints.soton.ac.uk/id/eprint/454507
ISSN: 0300-9246
PURE UUID: 9fb4ca75-79e7-492e-9d09-40eee9de9801
ORCID for Andrew L. Hector: ORCID iD orcid.org/0000-0002-9964-2163
ORCID for Ruomeng Huang: ORCID iD orcid.org/0000-0003-1185-635X
ORCID for William Levason: ORCID iD orcid.org/0000-0003-3540-0971
ORCID for Gillian Reid: ORCID iD orcid.org/0000-0001-5349-3468

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Date deposited: 14 Feb 2022 17:42
Last modified: 06 May 2022 01:43

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Contributors

Author: Victoria Greenacre
Author: Ruomeng Huang ORCID iD
Author: William Levason ORCID iD
Author: Vikesh Sethi
Author: Gillian Reid ORCID iD

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