Rare Earth Metal Complexes Supported by Ancillary Imidazolin-2-iminato Ligands
Résumé
The coordination chemistry of imidazolin-2-iminato ligands towards rare earth metals is reviewed. The structural characterisation 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, confirming 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, allowing 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 characterisation of the resulting complexes indicates that also neutral imidazolin-2-imines act as strong amido-type donor ligands towards rare earth metal ions.
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