Heterobimetallic dianionic guanidinate complexes of lanthanide and lithium: highly efficient precatalysts for catalytic addition of amines to carbodiimides to synthesize guanidines

A series of heterobimetallic dianionic guanidinate complexes of lanthanide and lithium, [Li(THF)(DME)]3Ln[μ-η2η1(iPrN)2C(NC6H4p-R)]3 [R=Cl, Ln=Nd (I), Y (II), La (III); R=H, Ln=Nd (IV)] were synthesized and fully characterized. These complexes were found to be highly efficient precatalysts for the addition of various primary and secondary amines, and aromatic and aliphatic diamines to carbodiimides to give the corresponding monoguanidine and biguanidine derivatives under mild condition (at 25–60 °C), which provides an efficient way for the synthesis of biguanidines compounds. The activity depends on the central metals and ligands: La>Nd>Y for the metals and [(iPrN)2C(NC6H4p-Cl)]2−>[(iPrN)2C(NC6H5)]2− for the ligands were observed.