1. Insight into Oxide-Bridged Heterobimetallic Al/Zr Olefin Polymerization Catalysts
- Author
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Harmen S. Zijlstra, Alexander Hofmann, Cédric Boulho, Peter H. M. Budzelaar, Sjoerd Harder, Molecular Inorganic Chemistry, Boulho, C., Zijlstra, H. S., Hofmann, A., Budzelaar, Petrus Henricus Maria, and Harder, S.
- Subjects
STRUCTURAL-CHARACTERIZATION ,Aluminate ,zirconium ,010402 general chemistry ,Photochemistry ,TERT-BUTYLALUMINUM ,01 natural sciences ,Medicinal chemistry ,Catalysis ,Dissociation (chemistry) ,Adduct ,chemistry.chemical_compound ,Transition metal ,LIQUID ALUMINUM ALKYLS ,TRIETHYLALUMINUM ,MONOMER-DIMER EQUILIBRIA ,010405 organic chemistry ,alkene polymerization ,bimetallic catalysis ,Organic Chemistry ,Cationic polymerization ,General Chemistry ,0104 chemical sciences ,HOMOGENEOUS CATALYSTS ,chemistry ,Polymerization ,bimetallic catalysi ,aluminum ,DENSITY ,synthetic methods ,synthetic method ,TRANSITION-ELEMENTS ,LIGANDS ,COMPLEXES ,Methyl group - Abstract
Reaction of (TBBP)AlMe⋅THF with [Cp*2 Zr(Me)OH] gave [(TBBP)Al(THF)-O-Zr(Me)Cp*2 ] (TBBP=3,3',5,5'-tetra-tBu-2,2'-biphenolato). Reaction of [DIPPnacnacAl(Me)-O-Zr(Me)Cp2 ] with [PhMe2 NH](+) [B(C6 F5 )4 ](-) gave a cationic Al/Zr complex that could be structurally characterized as its THF adduct [(DIPPnacnac)Al(Me)-O-Zr(THF)Cp2 ](+) [B(C6 F5 )4 ](-) (DIPPnacnac=HC[(Me)C=N(2,6-iPr2 -C6 H3 )]2 ). The first complex polymerizes ethene in the presence of an alkylaluminum scavenger but in the absence of methylalumoxane (MAO). The adduct cation is inactive under these conditions. Theoretical calculations show very high energy barriers (ΔG=40-47 kcal mol(-1) ) for ethene insertion with a bridged AlOZr catalyst. This is due to an unfavorable six-membered-ring transition state, in which the methyl group bridges the metal and ethene with an obtuse metal-Me-C angle that prevents synchronized bond-breaking and making. A more-likely pathway is dissociation of the Al-O-Zr complex into an aluminate and the active polymerization catalyst [Cp*2 ZrMe](+) .
- Published
- 2016
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