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Issue 44, 2014
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Niobium(V) and tantalum(V) halide chalcogenoether complexes – towards single source CVD precursors for ME2 thin films

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Abstract

A series of pentavalent niobium and tantalum halide complexes with thio-, seleno- and telluro-ether ligands, [MCl5(EnBu2)] (M = Nb, Ta; E = S, Se, Te), [TaX5(TeMe2)] (X = Cl, Br, F) and the dinuclear [(MCl5)2{o-C6H4(CH2SEt)2}] (M = Nb, Ta), has been prepared and characterised by IR, 1H, 13C{1H}, 77Se, 93Nb and 125Te NMR spectroscopy, as appropriate, and microanalyses. Confirmation of the tantalum(V)–telluroether coordination follows from the crystal structure of [TaCl5(TeMe2)], which represents the highest oxidation state transition metal complex with telluroether coordination structurally authenticated. The Ta(V) monotelluroether complexes are much more stable than the Nb(V) analogues. In the presence of TaCl5 the ditelluroether, CH2(CH2TetBu)2, is decomposed; one of the products is the dealkylated [tBuTe(CH2)3Te][TaCl6], whose structure was determined crystallographically. Crystal structures of [(MCl5)2{o-C6H4(CH2SEt)2}] (M = Nb, Ta) show ligand-bridged species. The complexes bearing β-hydrogen atoms on the terminal alkyl substituents have also been investigated as single source reagents for the deposition of ME2 thin films via low pressure chemical vapour deposition. While the tantalum complexes proved to be unsuitable, the [NbCl5(SnBu2)] and [NbCl5(SenBu2)] deposit NbS2 and NbSe2 as hexagonal platelets onto SiO2 substrates at 750 °C and 650 °C, respectively. Grazing incidence and in-plane X-ray diffraction confirm both materials adopt the 3R-polytype (R3mh), and the sulfide shows preferred orientation with the crystallites aligned predominantly with the c axis perpendicular to the substrate. Scanning electron microscopy and Raman spectra are consistent with the X-ray data.

Graphical abstract: Niobium(v) and tantalum(v) halide chalcogenoether complexes – towards single source CVD precursors for ME2 thin films

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Publication details

The article was received on 03 Sep 2014, accepted on 16 Sep 2014 and first published on 18 Sep 2014


Article type: Paper
DOI: 10.1039/C4DT02694B
Citation: Dalton Trans., 2014,43, 16640-16648
  • Open access: Creative Commons BY license
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    Niobium(V) and tantalum(V) halide chalcogenoether complexes – towards single source CVD precursors for ME2 thin films

    S. L. Benjamin, Y. Chang, C. Gurnani, A. L. Hector, M. Huggon, W. Levason and G. Reid, Dalton Trans., 2014, 43, 16640
    DOI: 10.1039/C4DT02694B

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