Samarium(III) tris(2,6-di-tert-butyl-4-methylphenoxide) (1), which is a highly coordinatively unsaturated complex, was prepared by the reaction of samarium(III) iodide with sodium 2,6-di-tert-butyl-4-methylphenoxide, and the crystal structure of its acetonitrile complex was determined by X-ray analysis. Complex 1 catalyzed the sequential Michael-Michael-aldol reaction of 3,3-dimethyl-2-butanone with