Lewis-acid behavior of tungsten hexafluoride towards mixed ligand systems, phosphine oxides and tridentate terpyridine
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Date
2024
Authors
Adamitz, Taylor Peter Karl
University of Lethbridge. Faculty of Arts and Science
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Lethbridge, Alta. : University of Lethbridge, Dept. of Chemistry and Biochemistry
Abstract
The Lewis-acid behavior of WF6 towards mixed ligand systems, phosphine oxides, and tridentate terpyridine has been investigated. Because of the known stability of 1 : 2 adducts of WF6 with main-group-donor ligands, the reaction of WF6 with stoichiometric amounts of the two bases pyridine and P(CH3)3 was studied, resulting in crystal growth of WF6(py){P(CH3)3}•CH2Cl2. The WF6(py){P(CH3)3} adduct adopts a capped trigonal prismatic geometry, prevalent for WF6 adducts. However, alongside the presence of the desired adduct, numerous side products were identified by NMR spectroscopy. Reactions of WF6 with OP(C2H5)3 and OP(C6H5)3 were conducted at both ambient temperatures and at –80 ºC invariably led to deoxofluorination with the formation of F2PR3 and [FPR3]+, R = C2H2, C6H5, being identified by NMR spectroscopy. Additionally, evidence for the new WOF4{OP(C2H5)}2 adduct was obtained by NMR spectroscopy. Lastly, the ability of WF6 to relinquish a fluoride when stabilized by nitrogen bases, alongside its ability to act as a fluoride acceptor, has been exploited to yield the [WF5(terpy)][WF7] salt as an autoionization product. This salt was fully characterized by multinuclear NMR and Raman spectroscopy, as well as X-ray crystallography and further studied computationally. The octacoordinated [WF5(terpy)]+ cation in [WF5(terpy)][WF7]•SO2 has a bicapped trigonal prismatic geometry as verified by the τ8 geometry index. Tungsten hexafluoride in the [WF7]– anion was displaced upon reacting the salt with SbF5•SO2, yielding [WF5(terpy)][SbF6].
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Keywords
fluorine , chemistry , inorganic , Gerken , Lewis-acid , Lewis-base , acid-base chemistry , autoionization , ligand scrambling , deoxofluorination , tungsten hexafluoride