Highly Active Immobilized Catalyst for Ethylene Polymerization: Neutral Single Site Y(III) Complex Bearing Bulky Silylallyl Ligand

Exploring the surface organometallic chemistry on silica of highly electrophilic yttrium complexes is a relatively uncommon endeavor, particularly when focusing on tris‐alkyl complexes characterized by Y−C σ‐alkyl bonds. A drawback with this class of complexes once grafted on silica, is the frequent occurrence of alkyl transfer by ring opening of siloxane groups, resulting in a mixture of species. Herein, we employed a more stable homoleptic yttrium allyl complex bearing bulky η 3 ‐1,3‐bis(trimethylsilyl)allyl ligand to limit this transfer reaction. This strategy has been validated by comparing the reactivity between [Y{ η 3 ‐1,3‐C 3 H 3 (SiMe 3 ) 2 } 3 ] and [Y(o‐CH 2 PhNMe 2 ) 3 ] with SiO 2–700 , where the undesired alkyl transfer reaction occurred for [Y(o‐CH 2 PhNMe 2 ) 3 ] leading to a bipodal [(≡SiO) 2 Y(o‐CH 2 PhNMe 2 )] as major surface species, 2 , while [Y{ η 3 ‐1,3‐C 3 H 3 (SiMe 3 ) 2 } 3 ] resulted selectively in a monopodal species, [(≡SiO)Y{η 3 ‐1,3‐C 3 H 3 (SiMe 3 ) 2 } 2 ], 1 . The materials obtained were characterized by DRIFT, solid state NMR, mass balance analysis and EXAFS. Catalyst 1 showed high activity compared to 2 in ethylene polymerization. The catalytic performance of this neutral catalyst 1 was extended to pre‐industrial scale in the presence of hydrogen and 1‐hexene. An unprecedented activity, up to 7400 g PE g cat −1 h −1 was obtained even with very low concentration of scavenger Al i Bu 3 (TIBA/Y=1.2). The obtained HDPE exhibited desired spherical particle morphology with broad molar mass distribution.