Structural diversity in substituted aminosilyl‐aminopyridinate metal (Zr or Fe) complexes: Synthesis, structures, and ethylene polymerization

Seven examples of chlorozirconium N‐[(N,N‐dimethylamino)dimethylsilyl]‐2‐pyridylaminates, mononuclear monoligand Zr[(RC5H4N)NSiMe2NMe2]Cl3LiCl(Et2O)2 (R = 4‐Me, Zr1; R = 5‐Me, Zr2; R = 5‐Cl, Zr3), chloro‐bridged dinuclear diligand [Zr{(RC5H4N)NSiMe2NMe2}Cl3]2 (R = 5‐Cl, Zr4; R = 4‐Cl, Zr5), and mononuclear triligand Zr[(RC5H4N)NSiMe2NMe2]3Cl (R = 6‐Me, Zr6; R = H, Zr7), have been prepared by the individual reactions of zirconium tetrachloride with the corresponding lithium N‐[(N,N‐dimethylamino)dimethylsilyl]‐2‐pyridylaminates of (RC5H4N)NHSiMe2NMe2 (R = 4‐Me, 1a; 5‐Me, 1b; 5‐Cl, 1c; 4‐Cl, 1d; 6‐Me, 1e; H, 1f), respectively. Besides seven coordination around zirconium core, Zr1–Zr5 adopt a distorted pentagonal bipyramid geometry with the ligand acting as a monoanionic η2:η1‐tridentate fashion; Zr6–Zr7 present capped trigonal prism geometry with the ligand as η2‐coordination with a pendant N (CH3)2 free. Extensively, the reactions of FeCl2 with lithiated (RC5H4N)NHSiMe2NMe2 (R = 4‐Me, 1a; 5‐Cl, 1c; 6‐Me, 1e) afford the corresponding dimeric complexes (R = 4‐Me, Fe1; 5‐Cl, Fe2; 6‐Me, Fe3), in which Fe1 and Fe2 exhibit C2 symmetry with each iron unit as a distorted trigonal bipyramidal geometry, while Fe3 specially possesses a centrosymmetric hour‐glass‐shaped core with each iron center as a distorted tetrahedral geometry. Upon activation with methylaluminoxane (MAO), zirconium complexes exhibit moderate to good activities toward ethylene polymerization and produce the polyethylenes with high molecular weight and broad dispersity. Sterically and electronically tuning tridentate aminosilyl‐aminopyridinate zirconium and iron complexes were synthesized and characterized. Influences of substituents and location significantly affected the diversity of coordination modes around metal ions along with solvents. The zirconium complexes showed good activities toward ethylene polymerization producing high molecular weight polyethylenes.