Partially fluorinated oxo-alkoxide tungsten(vi) complexes as precursors for deposition of WO_x nanomaterials

Abstract

The partially fluorinated oxo-alkoxide tungsten(VI) complexes WO(OR)4 [4; R = C(CH3)2CF3, 5; R = C(CH3)(CF3)2] have been synthesized as precursors for chemical vapour deposition (CVD) of WOx nanocrystalline material. Complexes 4 and 5 were prepared by salt metathesis between sodium salts of the fluoroalkoxides and WOCl4. Crystallographic structure analysis allows comparison of the bonding in 4 and 5 as the fluorine content of the fluoroalkoxide ligands is varied. Screening of as a CVD precursor by mass spectrometry and thermogravimetric analysis was followed by deposition of WOx nanorods.

Growth of WOx from Tungsten(VI) Oxo-Fluoroalkoxide Complexes with Partially Fluorinated β-Diketonate/β-Ketoesterate Ligands: Comparison of Chemical Vapor Deposition to Aerosol-Assisted CVD

“…Nanorods or nanowires were observed in samples grown at 500 °C with diameters measuring 250–350 nm. Bundled nanorods have been previously observed for deposits grown from similar tungsten oxo-alkoxide complexes at higher temperatures . In CVD (Figure b), nanocubes were deposited at temperatures above 350 °C.…”

Synthesis of tungsten oxo fluoroalkoxide complexes WO(OR)3L as precursors for growth of WOx nanomaterials by aerosol-assisted chemical vapor deposition

“…Oxygen-bound ligands such as oxo, alkoxide, β-diketonate and β-ketoesterate moieties have found use in single source precursors for the deposition of metal oxides because the preexisting metal oxygen bonding can facilitate conversion of the precursor to the oxide material during deposition [25,[34][35][36]. We have previously demonstrated that oxo alkoxide complexes of the type WO(OR) 4 (R = C(CH 3 ) 2 CF 3 and C(CF 3 ) 2 CH 3 ) and the dioxo derivative WO 2 (OR) 2 L (R = C(CF 3 ) 2 CH 3 , L = DME) are low temperature precursors to WO x films and nanorods, consistent with incorporation of the terminal oxo moieties into the deposits [23,41,42].…”

“…Fluorination of ligands has been shown to increase the volatility of complexes as a result of decreased intermolecular interactions due to the repulsion produced by the fluorine atoms [39,40]. Following this strategy, fluorinated tungsten oxo-alkoxide complexes have been used as WO x AACVD precursors [23,37,41,42]. We now report the synthesis of a series of fluorinated oxo alkoxide complexes WO(OR 3 )L [R = C(CH 3 ) 2 (CF 3 ), C(CH 3 )(CF 3 ) 2 ] that bear the chelating βdiketonate/ketoesterate ligands acetyl acetonate (acac), dipivaloylmethanate (dpm), ethyl acetoacetate (etac) and tert-butyl pivaloyl acetate (tbac) and demonstrate the use of WO(OC(CH 3 ) 2 (CF 3 ))tbac as a precursor for AACVD of WO x films and nanorods.…”

Metal–Organic Derivatives with Fluorinated Ligands as Precursors for Inorganic Nanomaterials

“…203 4 ] (OR f = TFTB, HFTB) adopt a monomeric structure. 207 The 5-coordinated tungsten center in the TFTB complex has square pyramidal geometry where the oxo ligand occupies the apical position and the four alkoxy ligands coordinate almost equatorially. The complex with HFTB ligand, on the other hand, has an additional DMSO ligand coordinated trans to the oxo ligand, which makes the geometry of the tungsten center pseudooctahedral.…”