Synthesis and characterization of bis(amidate) rare-earth metal amides and their application in catalytic addition of amines to carbodiimides

Abstract

Two new bis(amidate) lanthanide amides {LLn[N(SiMe₃)₂]·THF}₂ (H₂L = N,N′-(cyclohexane-1,2-diyl)-bis(4-tert-butylbenzamide); Ln = Sm(4), Yb(5)), which were prepared by the treatment of the bridged amide proligand H₂L with Ln[N(SiMe₃)₂]₃ in tetrahydrofuran, had been characterized by single-crystal X-ray diffraction and elemental analyses. Both complexes 4 and 5 and the three known isomorphs {LRE[N(SiMe₃)₂]·THF}₂ (RE = La(1), Nd(2), Y(3)) were successfully employed in the addition of amines to carbodiimides for the first time and were found to be efficient catalysts in the transformation at 60 °C under solvent-free conditions. The Nd-based catalyst 2 showed the highest reactivity and provided various guanidines with good functional group tolerance in high to excellent yields.