Catalytic behavior tuning via structural modifications of silylated‐diphosphine Ni(II) complexes for ethylene selective dimerization

The methylene spacers and an uncoordinated diphenylphosphine moiety in the scaffold of the CH3Si(CH2)n(PPh2)3 and Si(CH2PPh2)4‐type silylated diphosphine Ni(II) complex systems have a marked impact on their catalytic performance in selective ethylene dimerization. Ni(II)‐based precatalyst 1, bearing two methylene spacers in its framework, exhibited the highest catalytic activity of 1.29 × 108 g (molNi)‐1 h‐1, while precatalyst 3, with three methylene spacers, affords the highest product selectivity (88%) toward the C4 fraction. Crystallographic investigations revealed that the precatalyst 3 adopts the mononuclear bidentate binding mode and the steric constraints of its uncoordinated diphenylphosphine moiety may successfully tailor the catalytic environment of the catalyst. The precatalyst 4 may form a dinuclear complex and exhibits high catalytic activity by changing the ligand/Ni molar ratio. The high C4 selectivity of precatalyst 3 has been rationalized by density functional theory (DFT) calculations and found to be consistent with the experimental results. The study also revealed that designing new systems of Ni(II)‐based complexes and their systematic modifications may further provide potential and industrially viable catalyst systems for selective ethylene oligomerization. The methylene spacers and an uncoordinated diphenylphosphine moiety in the scaffold of the CH3Si(CH2)n(PPh2)3 silylated diphosphine Ni(II) complex systems have been realized to have a marked impact on their catalytic performance in selective ethylene dimerization.