Synthesis, Characterization, and Lewis Acid Behavior\nof [W(NC₆F₅)F₄]<i>_<i>x</i></i> and Computational Study of W(NR)F₄ (R = H, F, CH₃, CF₃, C₆H₅, C₆F₅), W(NC₆F₅)F₄(NCCH₃), and W(NC₆F₅)F₄(NC₅H₅)<i>_<i>n</i></i> (<i>n</i> = 1, 2)

Abstract

Amorphous [W­(NC₆F₅)­F₄]<i>_<i>x</i></i> has been synthesized by the reaction of [C₅H₅NH]­[W­(NC₆F₅)­F₅] with AsF₅ in CH₂Cl₂. The reaction of [W­(NC₆F₅)­F₄]<i>_<i>x</i></i> with CH₃CN yields monomeric W­(NC₆F₅)­F₄(NCCH₃), whereas reaction with\na sub-2-fold excess of C₅H₅N in CH₃CN results in quantitative conversion to W­(NC₆F₅)­F₄(NC₅H₅). Meanwhile, the reaction\nof W­(NC₆F₅)­F₄(NCCH₃) with\na large excess of C₅H₅N results in the precipitation\nof W­(NC₆F₅)­F₄(NC₅H₅)₂. These compounds have been characterized in\nthe solid state by Raman spectroscopy and in solution by multinuclear\nNMR spectroscopy. The crystal structures of W­(NC₆F₅)­F₄(NCCH₃) and W­(NC₆F₅)­F₄(NC₅H₅), as well as improved\nstructures of WOF₄(NC₅H₅)<i>_<i>n</i></i> (<i>n</i> = 1, 2),\nhave been obtained at low temperatures. Furthermore, density functional\ntheory (DFT-B3LYP) calculations have been conducted on the W­(NR)­F₄ (R = H, F, CH₃, CF₃, C₆H₅, C₆F₅) series as well as W­(NC₆F₅)­F₄(NCCH₃) and W­(NC₆F₅)­F₄(NC₅H₅)<i>_<i>n</i></i> (<i>n</i> = 1, 2), providing\noptimized gas-phase geometries, vibrational frequencies, molecular\norbitals, fluoride-ion affinities, and natural bond orbital (NBO)\nanalyses.