Chalcogenide fluorides of molybdenum (VI) and tungsten (VI).
thesisposted on 19.11.2015, 08:59 by Malcolm John. Atherton
The fluorination of molybdenum dioxydichloride, MoO2Cl 2, by either anhydrous hydrogen fluoride at elevated temperatures and pressures, or by xenon difluoride at low temperature produces a pale purple glass. This has been characterized, by infrared and 19 F n.m.r. spectroscopy, mass spectrometry and analytical data, as molybdenum dioxydifluoride, MoO2F2. In the reactions of MoO 2Cl2 with XeF2 evidence for the existence of MoO 2ClF has also been obtained. The controlled hydrolysis of tungsten oxytetrafluoride, WOF4, produces an extremely unstable solid which has been identified as tungsten dioxydifluoride, WO2F2, although definitive characterization has not been possible. The reactions of MoO2F 2 and the suspected WO2F2 with XeF2 do not produce the adducts XeF2.MoO2F2 or XeF2.WO2F2. Instead the oxytetra-fluorides are formed and these react with excess XeF2 to form the adducts XeF2.MoOF4 and XeF2.WOF4. Tungsten thiotetrafluoride, WSF4, and molybdenum thiotetrafluoride, MoSF 4, have been prepared for the first time. Both compounds were formed in reactions between antimony trisulphide, Sb2S3, and the appropriate hexafluoride at ~300. The compounds were characterized by infrared and 19F n.m.r. spectroscopy, and mass spectrometry. They are polymeric in the solid state, presumably being tetrameric like WOF 4. The reaction of tungsten thiotetrachloride, WSCl4, with XeF 2 also forms WSF4. The anions WSF5-, W2S2F9- and the series WSF 5-n Cln-, produced by the action of anhydrous HF on WSCl4, have been identified by 19F n.m.r. spectroscopy. The first transition-metal selenofluoride, WSeF4, has been prepared by heating Sb2Se3 and WF6 to 350 for 48 hrs. Mass spectrometry infrared and 19Fn.m,r, spectroscopy and analytical data were used to identify the product.