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′ = η5-C5Me4(SiMe3)) lanthanide
complexes were synthesized by the 1:2 acid–base reaction between
Cp′Ln­(CH2SiMe3)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.