MOLECULAR-STRUCTURE AND CHARGE-DISTRIBUTION IN ORGANOMETALLICS OF THE 4F AND 5F ELEMENTS .1. DIPOLE-MOMENT AND CHARGE-DISTRIBUTION OF THE ACTINOID(IV) TETRACYCLOPENTADIENIDES, AN(C5H5)4

The dipole moments of the tetracyclopentadienides, An(C5H5)4, of the lighter actinoids thorium, uranium and neptunium were measured in benzene solution. Although the compounds in the solid state have a quasi-T(d) molecular symmetry their dipole moments are not zero, owing to lowering of the molecular symmetry. The origin of the non-zero dipole moments is discussed.