Crystal and molecular structure of the adduct phosphorus pentafluoride–pyridine

Abstract

Crystals of (C₅H₅N),PF₅ are monoclinic, space group P2₁/n, with a= 6·056(2), b= 8·813(2), c= l3·854(2)Å, β= 97·34(2)°, Z= 4. The molecules exhibit an octahedral geometry with the plane of the pyridine ring staggered at 40·8° to one F₃PN plane. The four coplanar fluorine atoms are displaced away from the remaining fluorine, mean F–P–F 91·8(2)°. Rigid-body analysis reveals a pronounced librational motion about the F–P–N axis. Principal bond lengths (corrected for libration) are: P–F 1·607(1)(mean for the coplanar fluorines) and 1·594(3), P–N 1–898(4)Å. The structure was solved by direct methods and refined to R 0·052 for 823 diffractometer measured unique reflections.