Stabilisation of [WF5]+ and WF5 by Pyridine: Facile Access to [WF5(NC5H5)3]+ and WF5(NC5H5)2 |
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| Authors: | Douglas Turnbull Prof?Dr Paul Hazendonk Prof?Dr Stacey D Wetmore Prof?Dr Michael Gerken |
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| Institution: | Canadian Centre for Research in Advanced Fluorine Technologies and, Department of Chemistry and Biochemistry, University of Lethbridge, 4401 University Drive, Lethbridge, AB T1K 3M4 Canada |
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| Abstract: | The enhanced reactivity of WF5]+ over WF6 has been exploited to access a neutral derivative of elusive WF5. The reaction of WF6(NC5H5)2 with (CH3)3Si(NC5H5)]O3SCF3] in CH2Cl2 results in quantitative formation of trigonal-dodecahedral WF5(NC5H5)3]+, which has been characterised as its O3SCF3]? salt by Raman spectroscopy in the solid state and variable-temperature NMR spectroscopy in solution. The salt is susceptible to slow decomposition in solution at ambient temperature via dissociation of a pyridyl ligand, and the resultant WF5(NC5H5)2]+ is reduced to WF5(NC5H5)2 in the presence of excess C5H5N, as determined by 19F NMR spectroscopy. Pentagonal-bipyramidal WF5(NC5H5)2 was isolated and characterised by X-ray crystallography and Raman spectroscopy in the solid state, representing the first unambiguously characterised WF5 adduct, as well as the first heptacoordinate adduct of a transition-metal pentafluoride. DFT-B3LYP methods have been used to investigate the reduction of WF5(NC5H5)2]+ to WF5(NC5H5)2, supporting a two-electron reduction of WVI to WIV by nucleophilic attack and diprotonation of a pyridyl ligand in the presence of free C5H5N, followed by comproportionation to WV. |
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| Keywords: | fluorine Lewis acids redox chemistry tungsten X-ray crystallography |
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