Crystal and Molecular Structure of P(C6H5)5 · 0.5 THF

Pentaphenylphosphorus crystallizes from tetrahydrofuran (THF) as P(C ・0.5 THF (triclinic space group: P1̅, a = 10.095(4), b = 10.252(3), c = 12.725(3) A° , α = 71.21(1), β = 76.98(3), γ = 87.12(1)°, Z = 2). Its molecular structure is an almost perfect trigonal bipyramid with significantly longer axial than equatorial P-CPh bonds (P-C 1.982(2)/1.979(2), P-C 1.853(2)/1.845(2)/1.847(2) Å). It differs from the well established structure of solvent-free P(C (P. J. Wheatley, J. Chem. Soc. 2206 (1964)) in the relative orientation of the phenyl rings with respect to each other (axial rings) and with respect to the equatorial PC plane (equatorial rings) but not in the trigonal-bipyramidal (tbp) geometry at phosphorus. Differences in the geometry around the central atom had been found previously for Sb(C (square pyramid) and Sb(C · 0.5C (tbp) but not in As(C and As(C · 0.5 C (both tbp).