Stabilisation of [WF 5 ] + and WF 5 by Pyridine: Facile Access to [WF 5 (NC 5 H 5 ) 3 ] + and WF 5 (NC 5 H 5 ) 2

The enhanced reactivity of [WF 5 ] + over WF 6 has been exploited to access a neutral derivative of elusive WF 5 . The reaction of WF 6 (NC 5 H 5 ) 2 with [(CH 3 ) 3 Si(NC 5 H 5 )][O 3 SCF 3 ] in CH 2 Cl 2 results in quantitative formation of trigonal‐dodecahedral [WF 5 (NC 5 H 5 ) 3 ] + , which has been characterised as its [O 3 SCF 3 ] − 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 [WF 5 (NC 5 H 5 ) 2 ] + is reduced to WF 5 (NC 5 H 5 ) 2 in the presence of excess C 5 H 5 N, as determined by 19 F NMR spectroscopy. Pentagonal‐bipyramidal WF 5 (NC 5 H 5 ) 2 was isolated and characterised by X‐ray crystallography and Raman spectroscopy in the solid state, representing the first unambiguously characterised WF 5 adduct, as well as the first heptacoordinate adduct of a transition‐metal pentafluoride. DFT‐B3LYP methods have been used to investigate the reduction of [WF 5 (NC 5 H 5 ) 2 ] + to WF 5 (NC 5 H 5 ) 2 , supporting a two‐electron reduction of W VI to W IV by nucleophilic attack and diprotonation of a pyridyl ligand in the presence of free C 5 H 5 N, followed by comproportionation to W V .