title: Conformational analysis of triphenylphosphine ligands in stereogenic monometallic complexes: tools for predicting the preferred configuration of the triphenylphosphine rotor.
abstract: The extension of our simple model for predicting the propeller configuration of a triphenylphosphine ligand co-ordinated to achiral metal centres to include stereogenic metal systems is described. By considering nadir energy planes (NEP's) and a series of rigid-body calculations, a model has been developed to reliably predict the configuration of the triphenylphosphine rotor of stereogenic metal complexes. For complexes of the form [M(η(5)-C5H5)(PPh3)(L(1))(L(2))], where it is assumed that L(1) is larger than L(2), the configuration of the triphenylphosphine rotor may be predicted by viewing a Newman projection along the L(1)-M bond. In the orientation where the PPh3 unit is pointing vertically downwards and the orthogonal L(2) ligand is pointing to the right [i.e., an (RM)-configured complex, assuming that L(2) is ranked higher priority than L(1)], the conformation of L(1) can be expected to place the most sterically demanding substituent in the top-right quadrant. In cases where ligand L(1) still presents a steric incursion towards the PPh3 ligand (any part of L(1) other than H proximal to the PPh3 in the approximate zone -30° to +60° from the M-P bond) an (M)-configured rotor is expected, and when this interaction is not present a (P)-configured propeller is predicted. Without exception, these rules are consistent with all empirical data (>140 known crystal structures).
authors.affiliation: Faculty of Applied Sciences, University of the West of England, Frenchay Campus, Coldharbour Lane, Bristol, BS16 1QY, UK. james.costello@uwe.ac.uk.
authors.forename: James F
authors.initials: JF
authors.lastname: Costello
authors.forename: Stephen G
authors.initials: SG
authors.lastname: Davies
authors.forename: Elliott T F
authors.initials: ET
authors.lastname: Gould
authors.forename: James E
authors.initials: JE
authors.lastname: Thomson
mesh_terms: D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D009943:Organophosphorus Compounds / Q000737:chemistry*
chemical_list: D056831:Coordination Complexes; D008024:Ligands; D009943:Organophosphorus Compounds; C061896:triphenylphosphine