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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 η3‐1,3‐bis(trimethylsilyl)allyl ligand to limit this transfer reaction. This strategy has been validated by comparing the reactivity between [Y{ η3‐1,3‐C3H3(SiMe3)2}3] and [Y(o‐CH2PhNMe2)3] with SiO2–700, where the undesired alkyl transfer reaction occurred for [Y(o‐CH2PhNMe2)3] leading to a bipodal [(≡SiO)2Y(o‐CH2PhNMe2)] as major surface species, 2, while [Y{ η 3‐1,3‐C3H3(SiMe3)2}3] resulted selectively in a monopodal species, [(≡SiO)Y{η3‐1,3‐C3H3(SiMe3)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 gPE gcat−1 h−1 was obtained even with very low concentration of scavenger AliBu3 (TIBA/Y=1.2). The obtained HDPE exhibited desired spherical particle morphology with broad molar mass distribution. [ABSTRACT FROM AUTHOR]