Rare earth metal bis(alkyl) complexes bearing a monodentate arylamido ancillary ligand: Synthesis, structure, and Olefin polymerization catalysis

The reaction of Ln(CH2SiMe3)3(thf)2 with 1 equiv. of the amine ligand 2,6-iPr2C6H3NH(SiMe3) gave the corresponding amido-ligated rare earth metal bis(alkyl) complexes [2,6-iPr2C6H3N(SiMe3)]Ln(CH2SiMe3)2(thf) (Ln = Sc (1), Y (2), Ho (3), Lu (4)), which represent rare examples of bis(alkyl) rare earth metal complexes bearing a monodentate anionic ancillary ligand. In the case of Gd, a similar reaction gave the bimetallic complex Gd2(μ-CH2SiMe2NC6H3iPr2-2,6)3(thf)3 (5) through intramolecular C–H activation of a methyl group of Me3Si on the amido ligand by Gd–CH2SiMe3 and the subsequent ligand redistribution. Complexes 1–5 were structurally characterized by X-ray analyses. On treatment with 1 equiv of [Ph3C][B(C6F5)4] in toluene at room temperature, complexes 1–4 showed high activity for the living polymerization of isoprene. The 1/[Ph3C][B(C6F5)4] system showed high activity also for the polymerization of 1-hexene and styrene.