Photochemical Synthesis of Tungsten Pentafluoride, WF₅

Abstract

A new synthetic route for the synthesis of WF5 utilizing a mercury photosensitized reduction of tungsten hexafluoride with H2 is described. Crystals of WF5 were studied using single‐crystal X‐ray diffraction, resulting in the first‐reported crystal structure of WF5. Powder X‐ray diffraction studied at room‐temperature showed the compound was phase‐pure. The IR spectrum of WF5 was reinvestigated and interpreted with the use of solid‐state quantum‐chemical calculations using the DFT‐PBE0 density functional method. The compound synthesized herein was free of HF and moisture but may have contained minute amounts of WOF4, that were only observed in the IR spectrum.

Reactions of Molybdenum and Tungsten Oxide Tetrafluoride with Sulfur(IV) Lewis Bases: Structure and Bonding in [WOF4]4, MOF4(OSO), and [SF3][M2O2F9] (M = Mo, W)

“…As such, it is invariably isotypic with [MF 5 ] 4 (M = Nb, Mo, Ta, W; Figure a). The W–F b (b = bridging) bond lengths (2.111(3), 2.122(3) Å) would suggest symmetric fluorine bridging between tungsten centers, which is observed crystallographically for [MF 5 ] 4 and recently predicted in the gas phase for [MoF 5 ] 4 and [WF 5 ] 4 . Symmetric bridging is, however, in contrast to the expected trans influence of the WO bond in the W–F b ···WO moiety.…”

Stabilisation of [WVF4]+ by N‐ and P‐Donor Ligands: Second‐Order Jahn‐Teller Effects in Octacoordinate d1 Complexes

“…This is exacerbated further by its susceptibility to disproportionation under ambient conditions or upon slight warming [4] . Nevertheless, it is known to adopt a fluorine‐bridged, tetrameric structure in the solid state [6,7] and its F − ‐acceptor and Lewis‐acid behaviours were observed indirectly upon reduction of WF 6 to form [WF 5+ n ] n − ( n =1–3) salts, [8] as well as in a preliminary report on WF 5 (NCCH 3 ) [9] …”

“…Tungsten hexafluoride is the weakest oxidising agent of the transition‐metal hexafluorides, uniquely among them being unable to oxidise NO [1] or Si [2] . Thus, it is unsurprising that preparations of WF 5 are cumbersome and that its chemical properties remain largely unknown [3–6] . This is exacerbated further by its susceptibility to disproportionation under ambient conditions or upon slight warming [4] .…”

Lewis Acid Behavior of MoF5 and MoOF4: Syntheses and Characterization of MoF5(NCCH3), MoF5(NC5H5)n, and MoOF4(NC5H5)n (n = 1, 2)

“…Although improved geometric, thermodynamic, and/or spectroscopic data for MoF 5 and WF 5 have been collected since their first published syntheses in 1957 and 1968, respectively, − their Lewis acid behavior remains poorly understood. Calculated FIAs indicate that monomeric WF 5 (FIA = 472.8 kJ mol –1 ) is a slightly stronger Lewis acid than monomeric MoF 5 (FIA = 440.2 kJ mol –1 ), although both exist as fluorido-bridged tetramers in the solid state. , While MoF 5 and WF 5 are significantly stronger Lewis acids than BF 3 , they are weaker than SbF 5 (FIA = 503.3 kJ mol –1 ), which has been used as the threshold for Lewis superacidity…”

“…Calculated FIAs indicate that monomeric WF 5 (FIA = 472.8 kJ mol −1 ) 10 is a slightly stronger Lewis acid than monomeric MoF 5 (FIA = 440.2 kJ mol −1 ), 11 although both exist as fluorido-bridged tetramers in the solid state. 6,7 While MoF 5 and WF 5 are significantly stronger Lewis acids than BF 3 , they are weaker than SbF 5 (FIA = 503.3 kJ mol −1 ), 2 which has been used as the threshold for Lewis superacidity. 12 Despite its known Lewis acidity, there are few examples of MoF 5 complexes, and other than homoleptic [MoF 6 ] − , 13 magnetic susceptibility measurements.…”