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

Abstract

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.