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)(2)Br(2)afforded salt [P(CH3)(3)(C3F5)](2)[Sn(C2F5)(2)F-4]. When fluorotrimethyl[(Z)-pentafluoropropen-1-yl]phosphorane was treated with P(C2F5)(2)F the primarily produced anion is sufficiently nucleophilic to attack the propenyl group of the cation in beta-position to the phosphorus atom to yield zwitterionic [Me3PCF=C(CF3)-PF3(C2F5)(2)].