The barrier to internal rotation in metallocenes

Abstract It has been shown by calculation that the eclipsed forms of ferrocene and ruthenocene are more stable than their staggered forms. The main contribution to the energy difference is the induction energy of the metal in the potential field of the rings. Direct ring-ring electrostatic energy also favours the eclipsed forms by a small amount. The calculated barrier in ferrocene is in good agreement with an experimental estimate from electron diffraction.