This chapter contains sections titled: Introduction Cerium(IV) Compounds Samarium(II) Iodide, SmI2 Lanthanide β-Diketonates as Diels–Alder Catalysts Cerium(III) Chloride and Organocerium Compounds Cerium(III) Chloride and Metal Hydrides Scandium Triflate and Lanthanide Triflates Alkoxides and Aryloxides Lanthanide Metals Organometallics and Catalysis