Half-metallocene complexes of yttrium with amidinate ligands: Monoalkyl yttrium formation and C–H bond activation

The treatment of half-metallocene dialkyl yttrium complexes (C5Me4SiMe3)Y(CH2SiMe3)2(THF) (1a) and (C5Me4SiMe2Ph)Y(CH2SiMe3)(THF) (1b) with carbodiimide (RNCNR, R = tBu, Cy, iPr) resulted in two different kind of yttrium complexes bearing bis(amidinate) ligands. The reaction of complex 1a gave THF-free monoalkyl complexes (C5Me4Me3Si)Y(CH2SiMe3)[(RN)2C(CH2SiMe3)] (2a–c) as thermally robust crystals, while the reaction of complex 1b resulted in an ortho-metalated product 3, which contains a strained five-membered chelate ring formed by the C–H bond activation of the phenyl group. All resulted complexes were fully characterized by NMR spectroscopy and the structures of complexes 2a and 3 were confirmed by X-ray diffraction. Complexes 2a–2c show low to high activities for n-butyl acrylate polymerization to produce high molecular weight polymers.

The reaction of half-metallocene yttrium dialkyls complexes with carbodiimide ligands produces THF-free monoalkyl complexes or C–H bond activation product.Figure optionsDownload as PowerPoint slide