Rare-Earth Metal Diimide Complexes via Alkylaluminate Templating,Including a Ceric Derivative

Protonolysis of lanthanide tris(tetramethylaluminate)s with two equivalents of 2,6-diisopropylaniline affords La^III and Ce^III diimide compounds Ln(μ-NC₆H₃iPr₂-2,6)₂AlMe₂](thf)₄ featuring a bidentate AlMe₂-linked diimido ligand. As revealed for the corresponding Ce(GaMe₄)₃-reaction, formation of the diimide complexes proceeds via tetrametallic complexes of the type Ce{(μ-NC₆H₃iPr₂-2,6)(HNC₆H₃iPr₂-2,6)(MMe₃)}]₂ (Me=Al, Ga). Oxidation of the cerium(III) complex with hexachloroethane leads to a neutral Ce^IV diimide species. Partial protonolysis with phenylacetylene and hydrogenolysis via H₃SiPh give conclusive insights into the reactive coordination sites of such diimide complexes.