QUANTIFICATION OF LIGAND-LIGAND INTERACTIONS USING SOLID ANGLES

A method is described for quantifying the steric interaction (repulsio n) between two ligands. In the method the angular overlap between sphe res (atoms) from a common origin (a metal atom), in terms of linear co ne angles (the vertex angle of overlap, lambda) as well as solid angle s (the solid angle of overlap, Gamma, and the corrected solid angle of overlap, Gamma(C)) is measured. The methodology can be extended to me asure lambda, Gamma and Gamma(C) as functions of radial distance from the origin (metal atom) up to the limit of overlap. This variation of angular overlap with radial distance yields an angle of overlap (radia l congestion) profile. The algorithm to measure lambda, Gamma and Gamm a(C) has previously been developed in our solid angle methodology. Rad ial congestion profiles in terms of lambda, Gamma and Gamma(C) for som e simple molecules, e.g. Cr(CO)(5)PPh3, Cr(CO)(5)PMe3, MnRe(CO)(10) an d the use of the methodology to rationalise cis/trans isomer ratios in [(eta(5)-C5H3(SiMe3)(2))Mo(CO)(2)(L)I] are discussed.