Cyclopentadienyls and Phospholyls of the Group 3 Metals and Lanthanides

Cyclopentadienyls and variants have been the most employed ligands in the organometallic chemistry of the rare earth metals. Their typical, advantageous η5-binding mode allows occupation of several metal coordination sites and increases the solubility, while rendering the metal ion quite reactive. Hence, half-sandwich and metallocene complexes have been heavily used in synthesis, catalysis and small molecule activation. Sterically more encumbered Cp-ligands allowed stabilization of unusual electronic ground states, having enormous ramifications on the magnetic properties, primarily for single-molecule magnet design. Although requiring more elaborate synthetic protocols and hence far less common, the heteroatom-substituted phospholyls have also gained recently considerable attention.