Cyclopentadienyl-Like Ligand as a Reactive Site in Half-Sandwich Bis(amidinato) Rare-Earth-Metal Complexes: An Efficient Application in Catalytic Addition of Amines to Carbodiimides

A series of mixed Cp′/bis(amidinato) (Cp′ = η 5 -C 5 Me 4 (SiMe 3 )) lanthanide complexes were synthesized by the 1:2 acid–base reaction between Cp′Ln(CH 2 SiMe 3 ) 2 (THF) (Ln = Y, Dy, Er, Lu) and amidines. These Cp′/bis(amidinato) complexes showed excellent catalytic activity for the addition of amines to carbodiimides, yielding the corresponding guanidines. Isolation, structural characterization, and catalytic application of the binuclear lutetium amido complex showed clearly that the catalytic cycle was initiated by the dissociation of Cp′. These results demonstrated that Cp′, for the first time, acted as a reactive site to yield the active Ln–N species.