The catalytic behavior of heterocenes activated by TIBA and MMAO under a low Al/Zr ratios in 1-octene polymerization

The structural diversity of heterocycle-fused potassium cyclopentadienides

“…[10][11][12][13][14][15] Recently, we demonstrated the high efficiency of cyclopenta[b] thiophene Zr complexes in oligomerization of C 6 -C 10 a-olens, 16 and the promising catalytic properties of Zr ansa-complexes based on cyclopenta[1,2-b:4,3-b 0 ]dithiophene, indeno [1,2-b] indole and indeno [2,1-b]indole (Scheme 2, top) in polymerization of 1-octene. 17 In our experiments, heterocenes outperformed traditional cyclopentadienyl, indenyl and uorenyl sandwich Scheme 1 Donor heterocyclefused cyclopentadienes.…”

“…were synthesized according to previously reported procedures (see also 17 and Section S1 in the ESI †). 11-Phenyl-6H-indeno[1,2-b]indolizine 4 is a new compound that was prepared by Scheme 3 (see Section S1 in the ESI † for NMR spectra).…”

“…The molecular structure of these compounds is poorly studied; to date, only a few dichlorozirconium ansa-complexes have been characterized by X-ray diffraction analysis. 10,17,[19][20][21][22][23][24] Obviously, these data do not reect the entire spectrum of possible metal-ligand interactions in catalytic species due to the predominantly covalent nature of bonding in neutral LZrCl 2 complexes.…”

“…The analysis of the structures of heterocycle-fused cyclopentadienides allows us to conclude that the presence of annelated donor heterocycle instead of condensed benzene ring (Scheme 5) does not lead to signicant changes in the geometry of C5 and C6 rings compared to uorenide. Apparently, the possible causes of the difference observed in NMR spectra, and in the chemical behavior of zirconium complexes based on uorene and 5-7, 17 can be attributed to the difference in the electronic structure of these ligands.…”

“…This behavior indicates that heterocene ligands much more effectively stabilize the Zr cationic reaction center relative to traditional cyclopentadienides due to their electron-donor nature, 18 which entails increasing in catalytic activity and feasibility of using heterocenes at elevated temperatures. The structural diversity of heterocycle-fused cyclopentadienes permits a more variety in stereocontrol of a-olen insertion: rac-forms of ansa-zirconocenes based on heteroanalogs of indene allows to obtain isotactic polypropylene 19 or polypropylene elastomers; 20,21 Zr complexes based on heteroanalogs of uorene were successfully used in the synthesis of polypropylene elastomers, 11,14,15 isotactic poly(1-butene), 12 high MW atactic polyolens 17 and other prospective materials.…”