Cationic Aryl Complexes of the Rare-Earth Metals

Neutral rare-earth metal tri(aryl) complexes [Ln(C6H4-p-R)3(THF)2] (Ln = Lu, Sc; R = H, Me, Et), synthesized by reacting anhydrous metal trichloride with 3 equiv of the corresponding aryllithium, react with 1 or 2 equiv of [NR‘3H][BPh4] (R‘ = Et; R‘3 = PhMe2) to yield monocationic di(aryl) complexes [Ln(C6H4-p-R)2(THF)4]+[BPh4]- and dicationic mono(aryl) complexes [Ln(C6H4-p-R)(THF)5]2+[BPh4]-2, respectively. Single-crystal X-ray diffraction studies of the mono- and dicationic compounds [Sc(C6H5)2(THF)4]+[BPh4]- and [Lu(C6H5)(THF)5]2+[BPh4]-2 show distorted octahedral coordination geometry around the metal center in the cation. Kinetic studies for the reaction of the dicationic complex [Lu(C6H4-p-Me)(THF)5]2+[BPh4]-2 with pyridine suggest competition between C−H bond activation and insertion reactions.