Molecular structure of tris(pentafluoroethyl)phosphane P(C2F5)3

Abstract

The structure of tris(pentafluoroethyl)phosphane, P(C₂F₅)₃, has been determined in the solid state by in situ single crystal growth and subsequent X-ray diffraction and in the gas phase by electron diffraction. The experimental structure determinations have been supported by and compared to quantum chemical calculations at different levels of theory. P(C₂F₅)₃ prefers a conformation of C₃ symmetry with the CF₃ groups of the three C₂F₅ units oriented to the same side of the molecule as the phosphorus lone pair of electrons, leading to an estimated Tolman cone angle of 193° (solid) and 191° (gas), whereas a second stable conformer of C₃ symmetry, (only 5 kJ mol⁻¹ higher in energy) has a smaller Tolman cone angle of 171°. The structures are discussed in context with related molecules E(CF₃)₃ (E = N, P, As, Sb) as well as N(C₂F₅)₃ and P(C₂H₅)₃.