Kinetics and mechanistic insight into propylene polymerization with different metallocenes and various aluminium alkyls as cocatalysts

Modification of Methylaluminoxane‐Activated ansa‐Zirconocene Catalysts with Triisobutylaluminum—Transformations of Reactive Cations Studied by NMR Spectroscopy

“…As noted in related studies, [3,19,22,23] the signal assigned to the trialkyl dimer Al 2 A C H T U N G T R E N N U N G (m-Me) 2 …”

“…[1] This activator can be partly replaced, without loss of activity, by less expensive aluminum alkyls, such as triisobutylaluminum (AliBu 3 ). [2][3][4][5][6][7][8][9] It would, therefore, be of substantial practical interest to clarify the effects of AliBu 3 additions to MAO-activated zirconocene catalyst systems. NMR spectroscopic studies have shown that these catalyst systems predominantly contain the C 2 -symmetric AlMe 3 : a pair of substituted and/or bridged C 5 -ring ligands), in outer-sphere association with MAO-derived MeÀMAO À anions.…”

“…[2][3][4][5][6][7][8][9] It would, therefore, be of substantial practical interest to clarify the effects of AliBu 3 additions to MAO-activated zirconocene catalyst systems. NMR spectroscopic studies have shown that these catalyst systems predominantly contain the C 2 -symmetric AlMe 3 : a pair of substituted and/or bridged C 5 -ring ligands), in outer-sphere association with MAO-derived MeÀMAO À anions. [10][11][12][13][14][15] A primary task would be to clarify the way in which species of this type react with added AliBu 3 .…”

“…NMR spectroscopic studies have shown that these catalyst systems predominantly contain the C 2 -symmetric AlMe 3 : a pair of substituted and/or bridged C 5 -ring ligands), in outer-sphere association with MAO-derived MeÀMAO À anions. [10][11][12][13][14][15] A primary task would be to clarify the way in which species of this type react with added AliBu 3 . In continuation of previous inquiries, [16][17][18][19][20] we have investigated in detail, by use of 1 H and 13 C NMR spectroscopic methods, which transformations these cationic zirconocene complexes undergo upon addition of alkylaluminum compounds to MAO-activated catalyst systems derived primarily from rac-[Me 2 Si-A C H T U N G T R E N N U N G (ind) 2 ZrCl 2 ] (1) (ind: indenyl).…”

“…In addition to a broad MAOÀCH 3 signal in the range of d % 0 to À0.5 ppm and a sharp Al 2 Me 6 signal at À0.33 ppm, most of the remaining signals displayed can be attributed to the cationic species rac-[Me 2 SiA C H T U N G T R E N N U N G (ind) 2 ZrA C H T U N G T R E N N U N G (m-Me) 2 AlMe 2 ] + (species III). [10][11][12][13] Rather weak, broadened signals at d = 5.7-6.0, 5.1-5.2, and À1.6 to Abstract: When triisobutylaluminum (AliBu 3 ) is added to solutions containing methylaluminoxane (MAO) and…”