Acta Crystallographica Section B

Structural Science

Volume 55, Part 2 (April 1999)

research papers

Acta Cryst. (1999). B55, 203-208 [ doi:10.1107/S0108768198014177 ]

Conformational behaviour of bridging diphenylphosphido ligands

J. J. Barker and A. G. Orpen

Abstract: Data retrieved from the Cambridge Structural Database for crystal structures containing ( [mu] -diphenylphosphido) metal complexes, [M₂{ [mu] -PPh₂}] (where M is a d-block element), have been analysed to evaluate the conformational behaviour of these species. The observed distribution of torsion angles about the P-C bonds has been compared with the potential energy surface (PES) for phenyl rotations in a representative species [(AuBr)₂{ [mu] -PPh₂}]^- computed using the universal force field. Good agreement was obtained between the low-energy (<8 kJ mol^-1 above the global minimum) regions of the PES and the occupied regions of the two-dimensional P-Ph rotor conformation space. Phenyl ring rotations occur by coupled, geared disrotatory and uncoupled conrotatory motions of the phenyl groups in this and other classes of PPh₂ rotors.