Stabilisation of [WF5]+ and WF5 by pyridine: facile access to [WF5(NC5H5)3]+ and WF5(NC5H5)2

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Turnbull, Douglas
Hazendonk, Paul
Wetmore, Stacey D.
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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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Redox chemistry
Turnbull, D., Hazendonk, P., Wetmore, S. D., & Gerken, M. (2020). Stabilisation of [WF5]+ and WF5 by pyridine: Facile access to [WF5(NC5H5)3]+ and WF5(NC5H5)2. Chemistry, A European Journal, 26(30), 6879-6886.