Bildung eines zwitterionischen Einkomponentenkatalysators für die Ethenpolymerisation auf Basis von Butadiennickelkomplexen: ein alternativer Aktivierungsweg bei homogenen Ziegler-Natta-Katalysatoren später Übergangsmetalle

Abstract

Addition von B(C6F5)3 an den Butadienliganden in 1 liefert mit dem zwitterionischen Komplex 2 (charakterisiert durch Einkristall‐Röntgenbeugung; Ar=2,6‐Diisopropylphenyl) einen aktiven Katalysator für die Ethenpolymerisation. Die Bildung von 2 könnte Modellcharakter für einen Aktivierungsweg bei homogenen Ziegler‐Natta‐Katalysatoren später Übergangsmetalle ohne σ‐Alkylliganden haben.

Chelate Bis(imino)pyridine Cobalt Complexes: Synthesis, Reduction, and Evidence for the Generation of Ethene Polymerization Catalysts by Li+ Cation Activation

“…9a It was treated with 1 molar equiv of the “butadiene-magnesium” reagent in toluene solution. Quite differently from a series of related chelate bis(imine)nickel(II) dichloride complexes, , formation of a stable butadiene complex was not observed. Instead, reduction from (lig Me )CoCl 2 to (lig Me )CoCl again prevailed, and we isolated the cobalt(I) chloride complex ( 13 ) in 56% yield.…”

“…0.5 molar equiv of "butadienemagnesium". 13 As in the related cases described in the literature, 7,8 we did not observe the formation of a metal-dialkyl or metal-butadiene 11 products. Instead the cobalt(II) complex 10 was reduced to the corresponding cobalt(I) chloride 11.…”

“…In view of these surprising results we cannot rule out that the very low activity polyethylene formation that we had recently observed at the (lig)CoCl (11,13)/Li[B(C 6 F 5 ) 4 ] systems 18 was not intrinsic but may have been caused by some as yet unidentified cobalt alkyl contaminant. 19 With such low polymerization activities there is always the possibility that the observed reaction is caused by a minor high activity contamination.…”

“…Subsequent activation with, e.g., methylalumoxane (MAO) gave active ethene polymerization catalysts. Following the commonly accepted activation mechanisms 10,11 the systems derived from 3 are also homogeneous catalysts that might initially be lacking a metal-carbon σ-bond. Alkyl transfer from an R-[B]or R-[Al] --type counteranion could potentially again represent a mode of catalytic action at these special systems.…”

The (butadiene)zirconocene route to active homogeneous olefin polymerization catalysts

“…These were stable at room temperature, but rapidly rearranged to the transoid isomers 53 upon heating (see Scheme 16). Both the complexes 52a and 52b gave active ethene polymerization catalysts when exposed to the olefin (2 bar) in toluene solution in the presence of tri(isobutyl)aluminum [28]. However, it appeared that in these cases, the complexes 52 were not the intrinsic catalysts, in contrast to their Group 4 bent metallocene analogs, but required the presence of the trialkylaluminum agent for in situ activation (cf.…”