The Stereochemistry of Some Organic Derivatives of Group Vb Elements. Part X. The Crystal and Molecular Structure of Triphenylarsenic Difluoride

Abstract

The crystal structure of triphenylarsenic difluoride has been determined from three-dimensional X-ray diffractometer data. Crystals of Ph3AsF2 are orthorhombic, space group Pbcn, with four molecules of C18H15AsF2 in a unit cell of dimensions a = 6.270, b = 16.593, c = 14.519 Å; molecular symmetry C2 is required. The structure was solved by the heavy atom method and refined by full-matrix least-squares calculations to a final residual R of 0.054 for 979 intensities regarded as "observed" (I > 3σ(I)). The crystals contain well separated discrete molecules. The arsenic atom has near regular trigonal bipyramidal geometry with apical fluorine atoms (As—F 1.834(7) Å) and equatorial phenyl rings (mean As—C 1.925(5) Å). Idealized D3 symmetry is not achieved because of unequal rotations of the phenyl rings about the As—C bonds.