Fluorotrimethyl[(Z)-pentafluoropropen-1-yl]phosphorane: Structure,Bonding, and Reactivity

In this contribution we report on fluorotrimethyl(Z)-pentafluoropropen-1-yl]phosphorane as a phosphorus based fluorinating reagent. Its solid state structure can be described as a trigonal bipyramid featuring elongated axial bonds due to the formation of a 3-center 4-electron bond. Abstraction of the fluoride ion leads to a shortening of the axial P–C bond. Thus the title compound can be utilized for substitution of bromine with fluorine and for the transfer of fluoride ions onto electrophilic compounds. Reaction with Sn(C₂F₅)₂Br₂ afforded salt P(CH₃)₃(C₃F₅)]₂Sn(C₂F₅)₂F₄]. When fluorotrimethyl(Z)-pentafluoropropen-1-yl]phosphorane was treated with P(C₂F₅)₂F the primarily produced anion is sufficiently nucleophilic to attack the propenyl group of the cation in β-position to the phosphorus atom to yield zwitterionic Me₃PCF=C(CF₃)–PF₃(C₂F₅)₂].