MOLECULAR MECHANICS FORCE-FIELDS FOR CYCLOPENTADIENYL COMPLEXES

A self-consistent molecular mechanics force field is developed for the reproduction of structures and energy differences of bis-cyclopentadi enyl (Cp) complexes. The method is used to identify the forces which c ontrol Cp ring rotations, the conformations of substituted Cp complexe s, and provides an explanation for the existence of bent metallocenes of the alkaline earth and lanthanide metals and possibly for the bent structures of the divalent silicon group. The method provides an accur ate method of reproducing structures and can incorporate the structura l effects caused by crystal packing forces.