Tuning of nickel 2-phosphinophenolates – catalysts for oligomerization and polymerization of ethylene

Sterically and Polarity‐Controlled Reactions of tBuLi with PCH‐NR Heterocycles: Novel Heterocyclic P‐ and P,O‐Ligands and Preliminary Tests in Transition‐Metal Catalysis

“…The reaction of N-neopentyl-1,3-benzazaphosphole, occupying an intermediate position and affording a mixture in THF, can be controlled by the polarity of the medium. Addition of KOtBu leads to a strong preference [21] for CH lithiation, suppressing addition, whereas nonpolar hydrocarbon solvents have the opposite effect, furnishing addition products only, with a preference for tert-butylation at phosphorus and high diastereoselectivity for the trans adduct in this case. The less favored addition of the tertbutyl carbanion at C2 is completely suppressed in the case of the bulkier N-1-adamantyl group.…”

“…[20] While solutions of the weakly P-basic, rather p-acidic benzazaphospholes [6] catalysts, preferably performed at 80-100 8C, [21] , and the average molecular weight is considerably lower. Here, along with a small amount of liquid oligomers, a waxy polymer (m.p.…”

2-Substituted 8-(2-benzhydrylarylimino)-5,6,7-trihydroquinoline-N,N′ nickel dichlorides: Synthesis, characterization and catalytic behavior towards ethylene

“…Sticking to the concept of using N^N bidentate ligands, some N-heterocyclic compounds have been designed and successfully used in nickel-based pre-catalysts for ethylene oligomerization and/or polymerization [8e18]. In addition, numerous alternative nickel pre-catalysts have been reported, which employ various ligand types such as bidentate N^P [19e21], N^O [22e30], P^O [31,32], or tridentate N^N^N [33e46], N^N^O [47,48], N^P^N [49e51]. Within the N^N bidentate nickel pre-catalyst family, those bearing iminopyridyl ligation showed high activities for ethylene polymerization [8,9].…”

O‐Acylated 2‐Phosphanylphenol Derivatives – Useful Ligands in the Nickel‐Catalyzed Polymerization of Ethylene

“…Organometallic nickel complexes bearing chelating phosphanyl–enolate ligands are of great importance in the large‐scale production of linear α‐olefins in the Shell Higher Olefin Process (SHOP),1,2 but also allow the preparation of polyethylene and ethylene–olefin copolymers 2,3. Organonickel 2‐phosphanylphenolate catalysts4,5 or related in situ prepared catalyst systems5,6 likewise accomplish selective oligo‐ or polymerization of ethylene to linear α‐olefin chains and allow tuning of the molecular weights over a wide range for polymers by variation of the substituents at phosphorus4a and for low‐molecular‐weight oligomers by phosphane additives 4b,6c. P‐Basic dicyclohexylphosphanylphenolate catalysts are somewhat less selective and allow limited incorporation of α‐olefins yielding copolymers with various substituents at the main chain 7.…”