High cis -1,4 polyisoprene or cis -1,4/3,4 binary polyisoprene synthesized using 2-(benzimidazolyl)-6-(1-(arylimino)ethyl)pyridine cobalt(II) dichlorides

Abstract

Polyisoprene (PI) with a high content of cis‐1,4 (up to 95%) or cis‐1,4/3,4 binary structures was synthesized using a cobalt system in toluene. The cobalt system, which exhibited high activities (up to 3.50 × 106 g PI (mol Co)−1 h−1), contained a series of 2‐(benzimidazolyl)‐6‐(1‐(arylimino)ethyl)pyridine cobalt(II) dichlorides activated with ethylaluminium sesquichloride. The nature of the ligands and the reaction conditions significantly affected both the catalytic performance of the cobalt complexes as well as the structures of the resultant PI. The stereospecific polymerization of isoprene could be tuned via changing either the co‐catalyst or solvent: for example, increased content of 3,4 PI (up to 36.6%) was achievable in heptane in the presence of diethylaluminium chloride. Sequence distribution analysis by 13C NMR spectroscopy indicated that most 3,4 units occurred randomly in the PI chains. © 2013 Society of Chemical Industry

Pyridine–oxazoline and quinoline–oxazoline ligated cobalt complexes: Synthesis, characterization, and 1,3-butadiene polymerization behaviors

“…In recent years, research interest has been focused on the design and synthesis of well-defined single-site catalysts in order to gain precise control of the catalysis behavior and polymer composition [12][13][14][15]. Since the discovery of bis(arylimino)pyridine ligated Co(II) and iron(II) complexes as effective catalysts for ethylene polymerization/oligomerization [16,17], a variety of transition metal complexes bearing α-diimine, pyridinediimine, and their derivatives have been synthesized and exploited as catalyst precursors for olefin polymerization [18][19][20][21][22][23][24].…”

Polymerization of isoprene catalyzed by 2‐(methyl‐2‐benzimidazolyl)‐6‐(1‐(arylimino) ethyl) pyridine iron(III) trichloride with an additional donor

“…Ricci et al reported that equibinary cis ‐1,4/3,4 polyisoprene (PI) ( cis ‐1,4‐alt‐3,4 structure) could be synthesized with CoCl 2 (PRPh 2 ) 2 –MAO systems . High cis ‐1,4 polyisoprene or cis ‐1,4/3,4 binary PI using 2‐(benzimidazolyl)−6‐(1‐(arylimino)ethyl)pyridine cobalt(II) dichlorides was reported by our group . Bazzini et al reported a crystalline 3,4‐PI with the catalyst system diethylbis(2,29‐bipyridine)Fe/MAO .…”

“…Up to now, most studies have focused on ethylene oligo‐polymerization using late transition metal precatalysts, in particular N^N^N tridentate cobalt, nickel, and iron complexes . Only a few papers have been published concerning the homo‐ and copolymerization of 1,3‐dienes based on late transition metal complexes in combination with methylaluminoxane (MAO) or alkyl aluminium . Ricci et al reported that equibinary cis ‐1,4/3,4 polyisoprene (PI) ( cis ‐1,4‐alt‐3,4 structure) could be synthesized with CoCl 2 (PRPh 2 ) 2 –MAO systems .…”

Highlycis-1,4 selective polymerization of isoprene promoted by α-diimine cobalt(II) chlorides

“…cis ‐1,4 Polyisoprene, the structure adopted in natural rubber, was first synthetically prepared in 1956 using a system composed of AlR 3 ‐TiCl 4 in heptane . Subsequently many catalysts for cis ‐1,4‐polyisoprenes have been reported based on lanthanides (e.g., neodymium) and transition metals (e.g., chromium, iron, and cobalt). Two decades ago, α‐diiminometal (Ni or Pd) complexes were found as highly active catalysts for ethylene polymerization, this disclosure triggering extensive subsequent investigations by both academic and industrial groups on using ethylene or α‐olefin monomers .…”

“…Two decades ago, α‐diiminometal (Ni or Pd) complexes were found as highly active catalysts for ethylene polymerization, this disclosure triggering extensive subsequent investigations by both academic and industrial groups on using ethylene or α‐olefin monomers . Elsewhere cobalt complexes bearing NNN tridentate ligands were reported as efficient precatalysts toward isoprene polymerization . Although α‐diiminocobalt complexes were also synthesized and used to polymerize ethylene, there are no reports of bidentate cobalt complexes, to the knowledge of authors, being employed for isoprene polymerization.…”