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-NC₆ H₃ iPr₂ -2,6)₂ AlMe₂ ](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-NC₆ H₃ iPr₂ -2,6)(HNC₆ H₃ iPr₂ -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 H₃ SiPh give conclusive insights into the reactive coordination sites of such diimide complexes.