Hafnium and Zirconium Complexes Bearing ONN-Tridentate Ligands and Their Catalytic Properties toward Olefin Polymerization

Synthesis of Amido-quinoline Hafnium and Zirconium Complexes with Improved Performances toward Ethylene/1-Octene Copolymerization

“…Instead, a quartet resonance at 5.09 ppm is observed and assigned to CH 3 C H N, coupling with the migrating methyl group (C H 3 CHN, doublet at 1.21 ppm) as indicated by the spectrum of 1 H– 1 H COSY NMR (Figure S5). These results suggest the migration of methyl, the addition of imino group, and the formation of amino group, similar as previous reports involving imine-type ligands. , To investigate the thermal stability of the newly developed complexes, Hf1 was refluxed in C 7 D 8 at 110 °C for 6 h, and the NMR analysis confirmed no decomposition, as shown in Figure S51. In order to firmly determine the structure of the metal complexes, single crystals of complexes Hf1 and Hf4 were obtained by recrystallization of their toluene solutions at room temperature and characterized by X-ray diffraction.…”

“…This distance is significantly shorter by 0.361 Å than that of Hf1–N2 (2.411(4) Å), which is a dative bond between Hf center and the neutral quinoline-nitrogen donor. The C13–N1 distance is 1.460(6) Å, suggesting a typical C–N single bond. ,, These further confirm the amido-coordination in Hf1 , which is fully consistent with the result by NMR analysis. Complex Hf4 in Figure displays similar structural features, suggesting that other metal complexes should have similar coordination geometries.…”

“…Imino-quinoline compounds 1 – 4 (Scheme , D ) were prepared by acid-catalyzed condensation reactions with high purity and yield according to previous reports. − For the synthesis of metal complexes, HfMe 4 (or ZrMe 4 ) was in situ prepared by the reaction of HfCl 4 (or ZrCl 4 ) with 4 equiv of MeMgBr (3.0 M, Et 2 O solution) at −40 °C in toluene and then was used to react with compounds 1 – 4 directly in this study (Scheme , D ). ,, All the metal complexes were isolated as yellow solids in high yields (71–85%) and characterized by 1 H and 13 C NMR spectroscopy (Figures S3–S13). Thus, HfMe 4 (or ZrMe 4 ) was not separated or characterized because of its thermal instability at room temperature .…”