Vanadium(III) complexes containing phenoxy–imine–thiophene ligands: Synthesis, characterization and application to homo‐ and copolymerization of ethylene

Abstract

A set of vanadium(III) complexes, namely {SNO}VCl2(THF)2 (2a, SNO = thiophene‐(N═CH)‐phenol; 2b, SNO = 5‐phenylthiophene‐(N═CH)‐phenol; 2c, SNO = 5‐phenylthiophene‐(N═CH)‐4‐tert‐butylphenol; 2d, SNO = 5‐methylthiophene‐(N═CH)‐phenol; 2e, SNO = 5‐methylthiophene‐(N═CH)‐4‐tert‐butylphenol; 2f, SNO = 5‐methylthiophene‐(N═CH)‐2‐methylphenol; 2g, SNO = 5‐methylthiophene‐(N═CH)‐4‐fluorophenol), were synthesized by reaction of VCl3(THF)3 with phenoxy–imine–thiophene proligands (1a–g). All vanadium(III) complexes were characterized using elemental analysis and infrared and electron paramagnetic resonance spectroscopies. Upon activation with methylaluminoxane (MAO), vanadium precatalysts 2a–g proved active in the polymerization of ethylene (213.6–887.2 kg polyethylene (mol[V])−1⋅h−1), yielding high‐density polyethylenes with melting temperatures in the range 133–136 °C and crystallinities varying from 28 to 41%. The 2e/MAO catalyst system was able to copolymerize ethylene with 1‐hexene affording poly(ethylene‐co‐1‐hexene)s with melting temperatures varying from 126 to 102 °C and co‐monomer incorporation in the range 3.60–4.00%.