Bonding of H2, N2, Ethylene, and Acetylene to Bivalent Lanthanide Metallocenes: Trends from DFT Calculations on Cp2M and Cp*2 M (M = Sm, Eu, Yb) and Experiments with Cp*2Yb

The results of DFT calculations have been used to define the trends in the interactions of H 2, N 2, C 2 H 4, C 2 H 2, and C 2 Me 2 with the bivalent lanthanide metallocenes Cp 2 M (Cp = η 5 -C 5 H 5 ) and Cp* 2 M (Cp* = η 5 -C 5 Me 5 ), where M = Sm, Eu, Yb. These results, together with those previously published for the bonding of CO to Cp 2 M (M = Ca, Eu, Yb), suggest that the interaction of these ligands with the lanthanide metallocenes results from a subtle balance between attractive (dipole−dipole or dipole−induced dipole) and repulsive (electron−electron repulsion within the f shell) forces. The balance between the attractive and repulsive forces, and therefore the net bond energy, depends on the f-electron count in these bivalent lanthanide metallocenes. The computational results are compared with experimental observations on paramagnetic Cp* 2 Eu and diamagnetic ytterbocene, Cp* 2 Yb.