Chiral Zirconium Complexes with Bianiline-Based N₄-Donor Ligands

Abstract

Syntheses of new tetradentate ligands, containing a bianiline backbone and two additional heterocyclic N-donors, and of chiral zirconium complexes containing these ligands as dianions are reported. Crystal structures of some of these complexes show a preference for coordinating the two remaining ligands in a trans- rather than cis-orientation. Nevertheless, these complexes are moderately active in MAO-activated olefin polymerization in toluene solution at 50 °C. With propene, partly isotactic polypropene (55% mmmm) is obtained. These observations indicate that in cationic species generated in these reaction systems, the growing polymer chain and the olefin substrate occupy cis-coordination sites, while the heterocyclic N ligands adopt a screw-like trans orientation suitable to favor one of the enantiofacial orientations of the entering olefin substrate.

Synthesis, crystal structure and ethylene polymerization activity of zirconium complexes bearing mono-Cp and tridentate Schiff base [ONO] ligands

“…The wide bond angle Cl-Zr-Cl of complex 1 is the result of tridentate ligand, there is few example with wide angle for ethylene polymerization [25]. In any case, it is found that the activity of complex 1 is much higher than that of complex 2, which can be attributed to complex 2 bearing only one chloro ligand [14,26].…”

Synthesis of novel zirconium complexes bearing mono‐Cp and tridentate Schiff base [ONO] ligands and their catalytic activities for olefin polymerization

“…The wide bond angle of Cl-Zr-Cl of zirconium complex is the result of tridentate ligand, and there are examples with wide bond angles for ethylene polymerization. 34 The activity depends strongly on the substituent attached to the Cp ligand or Schiff base ligand. The catalytic activity (1) 2.5064(9) Zr-C(3) 2.536(4) Zr-Cl (2) 2.5090(10) Zr-C(4) 2.520(4) Zr-N (1) 2.341(3) Zr-C(5) 2.520(4) Cl(1)-Zr-Cl (2) 151 increased in the order 5 < 3 < 6 < 2 < 4 < 1 under the same conditions.…”

Uniqueness and versatility of iminopyrrolyl ligands for transition metal complexes

“…Brintzinger and co-workers [27] reported the preparation of diimino-dipyrrole ligand 40c with a chiral 6,6 0 -dimethyl-bianiline backbone and prepared its zirconium complex, (diimino-dipyrrolyl)ZrCl 2 (thf) (42c) (Eq. (12)).…”