SOLID ANGLES .3. THE ROLE OF CONFORMERS IN SOLID ANGLE CALCULATIONS

The values of the solid angles Omega for a range of commonly encounter ed ligands in organometallic chemistry (phosphines, phosphites, amines , arsines and cyclopentadienyl rings) have been determined. The solid angles were derived from a single energy conformer in a geometry const rained in a prototypical metal environment, i.e. with the ligand attac hed to Cr(CO),. This choice permits comparison with recent ligand repu lsive energies E(R) reported by Brown. Correlations between Omega, E(R ) and theta for the range of ligands studied typically gave correlatio n coefficients greater than 0.8. The values of the weighted average so lid angle <(Omega)over bar>, using an extension of the methodology by Brown and Mosbo, have also been determined. The minimum conformer soli d angle values are correlated with the weighted average solid angle (r = 0.96), suggesting that the minimum-energy conformation is a good ap proximate measure of steric size.