Synthesis, structure and reactivity of new yttrium bis(dimethylsilyl)amido and bis(trimethylsilyl)methyl complexes of a tetradentate bis(phenoxide) ligand

Abstract

The reactions of a bulky amino-methoxy bis(phenolate) ligand H 2L with Y(CH 2SiMe 3) 3(THF) 2 and Y[N(SiHMe 2) 2] 3(THF) 2 under mild condition leads to the selective formation of the thermally stable complexes [L]Y(CH 2SiMe 3)(THF) ( 1) and [L]Y[N(SiHMe 2) 2](THF) ( 2). The X-ray structures revealed very similar binding of the [ONOO] ligand core to the metal for both complexes, which feature an octahedral geometry involving coordination of the methoxy side-arm of the ligand and of a remaining THF molecule. 1H-NMR spectroscopy indicates that the solid state structure of 1 and 2 is retained in hydrocarbon solutions with THF coordinated to yttrium. Alkyl complex 1 showed no activity in ethylene polymerization, presumably due to the presence of coordinated THF. The amido complex 2 catalyzed sluggishly the polymerization of methyl methacrylate to give isotactic-rich PMMA but is very active for the ring-opening polymerization of ε-caprolactone.