Binding modes of a dimethyliminopentanone ligand on nickel pre-catalysts toward olefin polymerization

Nickel complexes prepared using a 4-(2,6-diisopropylphenylimino)-3,3-dimethylpentan-2-one ligand framework are shown. The potassium salt of the ligand is obtained by deprotonation with KH in diethyl ether. Potassium 4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olate can then be reacted with Ni(PMe3)2(η1-CH2Ph)Cl to yield 4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olato-κ1O](η1-CH2Ph)(PMe3)2Ni (1). The potassium salt of the ligand can also be reacted with Ni(PMe3)(η3-CH2Ph)Cl to yield bis(4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olato-κ2N,O](η1-CH2Ph)2Ni2 (2) or 4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olato-κ2N,O](η1-CH2Ph)(PMe3)Ni (3), depending on the reaction conditions. The addition of five equivalents of B(C6F5)3 to 1, 2, or 3 yields catalytically active species for the homopolymerization of ethylene. The polymer products are described by a single molecular weight distribution, consistent with the presence of a single active site.

Potassium 4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olate can then be reacted with Ni(PMe3)2(η1-CH2Ph)Cl to yield 4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olato-κ1O](η1-CH2Ph)(PMe3)2Ni (1). The potassium salt can also reacts with Ni(PMe3)(η3-CH2Ph)Cl to yield bis(4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olato-κ2N,O](η1-CH2Ph)2Ni2 (2) or 4-(2,6-diisopropylphenylimino)-3,3-dimethyl-pent-2-en-2-olato-κ2N,O](η1-CH2Ph)(PMe3)Ni (3), depending on reaction conditions. All three species are active toward homopolymerization of ethylene when activated with B(C6F5)3.Figure optionsDownload as PowerPoint slide