CONFORMATIONS OF DIPHOSPHITES: CRYSTALLOGRAPHY AND MOLECULAR MODELLING STUDIES. Dianne D. Ellis and A. Guy Orpen. School of Chemistry, University of Bristol, Bristol, BS8 1TS, UK
X-ray diffraction studies have been performed on a series of diphosphites1 and their chelate complexes (see below). Such bidentate phosphite ligands have attracted attention because of their potential applications in asymmetric hydroformylation catalysis.2
The structures and conformations of these and related species were analysed using the CAChe2 and Cerius23 modelling packages and compared with those of related compounds with known structures. Molecular mechanics (MM), using the MM2 and UFF force fields implemented within CAChe and Cerius2 packages respectively, were employed to compute minimum energy conformations for each compound. Force field parameter modifications that allowed good agreement between the solid state and minimised structures will be reported. The Cambridge Structural Database5 was used to provide estimates for bond and angle parameters used. MM studies will also be presented which shed light on the pathways for confomational interconversion in these systems.
References
1. M.J. Baker et al., J. Chem. Soc. Chem. Commun., 1991, 803.
2. CAChe Scientific Software, CAChe Scientific Inc., USA.
3. Cerius2, Molecular Simulations Inc., Cambridge, UK.
4. E. Billinget al., US Pat. 4,769,498, 1992, (to Union Carbide).
5. F.H. Allen et al., Acc. Chem. Res., 1983, 16, 146; F.H. Allen et al., J. Chem. Inf.Comput. Sci., 1987, 31, 187.