Valence-bond isomer chemistry. Part IV. The valence-bond isomers of pentakis(pentafluoroethyl)pyridine

Abstract

Reaction of pentafluoropyridine with tetrafluoroethylene and caesium fluoride in dimethylformamide produces, inter alia, perfluoro-4-ethyl-, -2,4-diethyl-, -2,4,5-triethyl-, -2,3,4,6-tetraethyl-, and -pentaethyl-pyridines. In perfluoro-n-pentane solution, the last compound is isomerized by u.v. light to pentakis(pentafluoroethyl)-1-azabicyclo[2,2,0]hexa-2,5-diene, which in turn forms the corresponding 1-azatetracyclo[2,2,0,0^2,6,0^3,5]hexane. These valence-bond isomers show substantial thermal resistance to rearrangement; in hexafluorobenzene solution, the half-life at 170 °C of the hexadiene is 104 h and that of the hexane is 1·1 h.