Ethylene homopolymerization with P, O‐chelated nickel catalysts

Abstract

SynopsisAbstraction of phosphine from the nickel(I1) P, 0-chelated complexes, Ni[Ph, PCH=C(Ph)O] (Ph)(PPh,), and related species converts them from olefin oligomerization to olefin polymerization catalysts. Phosphine acceptors such as Rh(acetylacetonate)(C2H4)2 or Ni(l,5-cyclooctadiene), are most effective. Alternatively, nickel complexes-in which the phosphine ligand is replaced with weakly coordinated pyridine can be prepared. These active, homogeneous catalysts can be tuned to give either low or high molecular weight, linear low or high density polyethylene. Depending on the diluent, the same catalytic complex can be used as heterogeneous or homogeneous catalyst. They are tolerant of oxygenated, hydroxylic, or polar molecules that would poison normal early transition metal-based Ziegler-Natta catalysts. In fact, the polymerizations can be run in solvents such as ethanol or acetone, but hydrocarbon solvents are preferred.

An Efficient Keim‐Type Catalyst Based on an Electron‐Poor P,O‐Chelate; Tuning the Selectivity of Ethylene Oligomerisation towards Short α‐Olefins

“…Overall, the effect observed by adding BF 3 is reminiscent of the properties of [Ni{Ph 2 PC 6 H 4 C(O) O}(Me-2-allyl)], [16] which upon addition of B(C 6 F 5 ) 3 shifts ethylene oligomerisation towards the formation of lowweight olefins (butene and hexene). [17] Finally, we noted that mixing complex 4 with Ni(cod) 2 in excess afforded, as expected, [11,18,19] a catalyst which polymerises ethylene. Its activity compares with that of 1a, but analysis of the polymer reveals that the polyethylene chains are considerably shorter (M w = 650 g mol -1 ) than those obtained with 1a (M w = 4500 g mol -1 ) under similar conditions.…”

Transition metal complexes of triphosphorus macrocycles: A new class of homogeneous olefin polymerisation catalysts

“…Additionally, since 7 is a compound of d 10 Ni(), it may be relatively resistant to coordinating additional ligands. In general, most ethene/CO co-polymerisation catalysts are cationic palladium complexes which contain bidentate phosphines and weakly coordinating anions; 40 there are relatively few nickel based co-polymerisation catalysts known, 41 in part due to the facile formation of Ni(CO) 4 . Similar reactions were attempted with compound 3 although no activity was observed.…”

Coordination chemistry of a mixed donor bidentate ligand with nickel. A tetrameric enolate of sodium that binds a phosphine donor

“…The discovery that certain nickel(I1) complexes incorporating mixed P,O donor ligands were effective catalyst precursors for ethylene oligomerization reactions in the so-called ShellHigher-Olefin-Process (SHOP) (1-7) has sparked a number of groups to devise new ancillary ligands that can be utilized (8)(9)(10)(11)(12)(13)(14). The original preparation (1) involved reaction of a ketophosphorus ylid of the type P h , P C H C O P h with Ni(COD), and PPh3 to produce, after phenyl transfer, the complex Ni(Ph)PPh,[Ph,PCH=C(O)Ph].…”