Rare Earth Metal Complexes Supported by Ancillary Imidazolin‐2‐iminato Ligands

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AbstractThe coordination chemistry of imidazolin‐2‐iminato ligands towards rare earth metal atoms is reviewed. The structural characterization of a large number of mono‐, bis‐ and tris(imidazolin‐2‐iminato) complexes – in most cases scandium, yttrium, gadolinium, and lutetium complexes – reveals almost exclusively the formation of mononuclear complexes with very short metal–nitrogen bonds, which confirms the ability of imidazolin‐2‐iminato ligands to efficiently act as imido‐type 2σ,4π‐electron donors. In particular, mono(imidazolin‐2‐iminato) metal dichlorides proved to be excellent starting materials for the introduction of alkyl, amido, cyclopentadienyl, cyclooctatetraenyl, and carboranyl ligands and also for the preparation of efficient pre‐catalysts for ring‐opening, hydroamination and hydrosilylation reactions, which allow to establish imidazolin‐2‐iminato ligands as novel valuable members of the growing family of ancillary ligands in organo rare earth metal and organolanthanide chemistry. In addition, the coordination chemistry of several imidazolin‐2‐imine‐hybrid ligands such as cyclopentadienyl‐imine and pincer‐type diimine ligands is described, and the structural characterization of the resulting complexes indicates that also neutral imidazolin‐2‐imines act as strong amido‐type donor ligands towards rare earth metal ions.