Abstract
A row of dimeric diisobutylaluminum aryloxides bearing different sterically crowded substituents in ortho-positions of the aryl ligand [(ArO)AliBu2]2 (ArO = 2-tBu-C6H4O (AlTBP), 2-Me,6-tBu-C6H3O (AlMTBP), 2,6-iPr2-C6H3O (AlDIPP), 2-Ph-C6H4O (AlPP), 2,6-Ph2-C6H3O (AlDPP), 1-C10H7O (AlN-1)) was synthesized. The Molecular structures of AlMTBP, AlDIPP, AlPP, AlDPP, and AlN-1 have been determined by X-ray crystallography. All dimeric diisobutylaluminum aryloxides were tested as activators of rac-Et (2-MeInd)2ZrMe2 in homopolymerization of ethylene, propylene, copolymerization of ethylene with propylene and terpolymerization of ethylene/propylene/5-ethylidene-2-norbornene. It was shown that only AlMTBP and AlDPP work as effective activators in all polymerization processes, with activity of AlMTBP system being significantly higher than that of AlDPP. The evaluation of dimerization energies of synthesized aryloxides by means of DFT calculations have shown AlMTBP and AlDPP to form the least stable dimers. The activation of rac-Et (2-MeInd)2ZrMe2 was modeled as bonding of diisobutylaluminum aryloxide with zirconocene followed by the first insertion of ethylene into Zr+–Me bond. As per that model, DFT calculations demonstrated the process to be the most favorable for AlMTBP and AlDPP which well corresponds to experimental observations.
Published Version
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