Synthesis, characterization, and 1,3-butadiene polymerization studies of Co(II), Ni(II), and Fe(II) complexes bearing 2-(N-arylcarboximidoylchloride)quinoline ligand

Abstract

A series of Co(II), Ni(II), and Fe(II) complexes supported by quinolinylimidoylchloride ligands [2-(N-ArN=CCl)C9H6N]MtBr2 (Ar=2,6-iPr2C6H3, M=Co (1a), Mt=Ni (2a), Mt=Fe (3a); Ar=2,6-Et2C6H3, Mt=Co (1b), Mt=Ni (2b), Mt=Fe (3b); Ar=2,6-Me2C6H3, Mt=Co (1c), Mt=Ni (2c), Mt=Fe (3c); Ar=C6H5, Mt=Co (1d), Mt=Ni (2d), Mt=Fe (3d); Ar=4-ClC6H4, Mt=Co (1e), Mt=Ni (2e), Mt=Fe (3e); Ar=4-OMe-C6H4, Mt=Co (1f), Mt=Ni (2f), Mt=Fe (3f)) were synthesized. The solid structure of ligand c, complexes 1e and 2a were characterized by single crystal X-ray analysis, showing that 1e was tetra-coordinate with a distorted tetrahedral geometry and 2a was penta-coordinate with a distorted trigonal bipyramid configuration. The imidoylchloride Co(II) and Ni(II) complexes (1a and 2a) activated by ethylalumium sesquichloride (EASC) displayed higher activities than did the aldimine-based Co(II) and Ni(II) complex (1A and 2A). The Co(II)-, Ni(II)-, and Fe(II)-based complexes exhibited different stereospecificities and afforded polybutadienes with different molecular weights due to the nature of the metal centre and the environment of the ligand. The imidoylchloride Co(II) complexes exhibited much better temperature tolerance, affording polymer in a high yield of 93.4% even at 80°C.