DYNAMICS AND MOLECULAR AGGREGATION IN CRYSTALLINE [(M(C5H5))(3)(MU(3)-ETA(2)ETA(2)ETA(2)-C(6)H(5)R)] [M=CO, R=CH(PH)ME, CH(2)CH(2)PH OR CHCHME, M=RH, R=H] CLUSTERS

The intermolecular aggregation in crystalline arene clusters of the type [{M(C5H5)}(3)(mu(3)-eta 2:eta(2):eta(2)-C(6)H(5)R)] [M = Co, R = CH(Ph)Me, CH(2)CH(2)Ph or CHCHMe; M = Rh, R = H] has been investigated by atom-atom packing potential-energy calculations and computer graphics. The ease of reorientation of the arene fragments and of the cyclopentadienyl ligands in the solid state has been investigated by calculating intramolecular and intermolecular potential-energy barriers. It has been shown that, except for the benzene ligand in [{Rh(C5H5)}(3)(mu(3) eta-(2):eta(2):eta(2)-C6H6)], the facial arenes cannot undergo reorientation in the solid state, whereas the reorientational motion of the cyclopentadienyl ligands is under intramolecular control.