Recent Progress in the Chemistry of Rare Earth Metal Alkyl and Hydrido Complexes Bearing Mono(cyclopentadienyl) Ligands

The acid–base reactions between rare earth tris(alkyl) complexes and silylene-linked cyclopentadiene–amines and –phosphines afford straightforwardly the corresponding cyclopentadienyl–amido and –phosphido rare earth alkyl complexes, respectively. This method can also be utilized for the synthesis of rare earth bis(alkyl) complexes bearing mono(cyclopentadienyl) ligands such as C5Me4SiMe3. The reaction of the alkyl complexes with H2 or PhSiH3 readily gives the corresponding hydrido complexes; in the case of the bis(alkyl) complexes bearing the C5Me4SiMe3 ligand, a novel type of rare earth polyhydrido cluster has been isolated and structurally characterized. The silylene-linked cyclopentadienyl–arylamido and –phosphido rare earth alkyl complexes act as excellent catalyst precursors for the dimerization of terminal alkynes and hydrosilylation of olefins, respectively. The rare earth polyhydrido clusters exhibit unique reactivities toward unsaturated organic substrates such as lactones, nitriles, and olefins.