title: Tuning ligand electronics and peripheral substitution on cobalt salen complexes: structure and polymerisation activity.
abstract: A series of cobalt salen complexes, where salen represents an N2O2 bis-Schiff-base bis-phenolate framework, are prepared, characterised and investigated for reversible-termination organometallic mediated radical polymerisation (RT-OMRP). The salen ligands contain a cyclohexane diimine bridge and systematically altered para-substituted phenoxide moieties as a method to examine the electronic impact of the ligand on complex structure and reactivity. The complexes are characterised by single crystal X-ray diffraction, cyclic voltammetry, X-ray photoelectron spectroscopy, electron paramagnetic resonance spectroscopy and computational methods. Structural studies all support a tailorable metal centre reactivity altered by the electron-donating ability of the salen ligand. RT-OMRP of styrene, methyl methacrylate and vinyl acetate is reported and suggests that cobalt-carbon bond strength varies with the ligand substitution. Competing β-hydrogen abstraction affords long-chain olefin-terminated polymer chains and well controlled vinyl acetate polymerisations, contrasting with the lower temperature associative exchange mechanism of degenerative transfer OMRP.
authors.affiliation: Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, BC V5A 1S6, Canada. tim_storr@sfu.ca.
authors.forename: Linus
authors.initials: L
authors.lastname: Chiang
authors.forename: Laura E N
authors.initials: LE
authors.lastname: Allan
authors.forename: Juan
authors.initials: J
authors.lastname: Alcantara
authors.forename: Michael C P
authors.initials: MC
authors.lastname: Wang
authors.forename: Tim
authors.initials: T
authors.lastname: Storr
authors.forename: Michael P
authors.initials: MP
authors.lastname: Shaver