achieved by the use of samarium diiodide in catalytic amounts together with mischmetall (an alloy of the light lanthanides) as a coreductant. Plausible catalytic schemes are proposed. In addition, organocerium and -lanthanum reagents have been obtained from samarium diiodide catalysed reactions between organic halides and cerium or lanthanum metal, giving a newroute to organolanthanoid compounds. It also