Effect of an alkyl substituted in salen ligands on 1,4‐Cis selectivity and molecular weight control in the polymerization of 1,3‐butadiene with (salen)Co(II) complexes in combination with methylaluminoxane

Abstract

The effect of an alkyl substituted in the aromatic ring of the salen ligand on the polymerization of butadiene (Bd) with (salen)Co(II) complexes in combination with methylaluminoxane (MAO) was investigated. The activity for the polymerization of Bd was influenced significantly by the introduction of alkyl groups at the 3,3 0 ,5,5 0positions in the aromatic ring of the salen ligand, and both the polymerization rate and 1,4-cis contents increased in the following order with respect to the alkyl group: H < CH 3 < t-C 4 H 9 . This is in good agreement with the bulkiness of the alkyl groups. The activity for the polymerization of the (salen)Co(II) complex possessing t-C 4 H 9 at the 3,3 0 -positions was higher than that of the (salen)Co(II) bearing t-C 4 H 9 at the 5,5 0 -positions. Thus, the introduction of bulky substituents at the 3,3 0 -positions of the salen ligand was an important factor in achieving both high activity and high 1,4-cis selectivity in the polymerization of Bd with (salen)Co(II) complexes in combination with MAO.

Synthesis, characterization, and butadiene polymerization of iron(III), iron(II) and cobalt(II) chlorides bearing 2,6-bis(2-benzimidazolyl)pyridyl or 2,6-bis(pyrazol)pyridine ligand

“…Cobalt complexes supported by Table 5 Polymerization of 1,3-butadiene with 2,6-bis(2-benzimidazolyl)pyridine or 2,6-bis(pyrazolyl)pyridine iron and cobalt complexes. [25,26,29] are likely to give cis-1,4 structure. And, such p-donating ligand maybe favor cis-1,4 coordination of butadiene with cobalt center followed by quick insertion to terminal carbon of cobalt allylic polymer chain [24].…”

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

“…For example, (salen)cobalt(II) [25] and bis(salicylaldiminate) cobalt(II) [26] were reported to be highly active for cis-1,4 polymerization of 1,3-butadiene. Cobalt dichloride complexes bearing various tridentate ligands such as 2,6-bis(imino)pyridine [6,27], 2,6-bis(pyrazol)pyridine [28], bis(N-arylcarboximidoylchloride)pyridine [29], 2-arylimino-6-(alcohol) pyridine/2-arylamino-6-(alcohol) pyridine [30], and 3-aryliminomethyl-2-hydroxybenzaldehyde [31] afforded cis-1,4 polybutadienes in high yields.…”

Polymerization of 1,3-butadiene catalyzed by ion-pair cobalt complexes with (benzimidazolyl)pyridine alcohol ligands

“…More recently, research efforts have been made on the design of welldefined and highly active cobalt complexes ligated by bi-, trior multi-dentate organic ligands. For example, (salen)cobalt(II) [( − ONNO − )Co] [25] and bis(salicylaldiminate)cobalt(II) complexes [(NO − ) 2 Co] [26], dinuclear cobalt(II) complexes with 3-aryliminomethyl-2-hydroxybenzaldehyde ligands [( -L) 2 Co 2 ( -OAc) 2 ] [27], cobalt dichloride complexes bearing neutral tridentate ligands [(NNN)CoCl 2 ] [28][29][30][31][32][33][34][35][36] (such as 2,6-bis(imino)pyridine, bis(benzimidazolyl)amine, 2,6-bis(benzimidazolyl)pyridine or 2,6-bis(pyrazol)pyridine ligands) have achieved high activity and high cis-1,4 selectivity in the polymerization of butadiene in combination with MAO, MMAO or ethylaluminum sesquichloride (EASC).…”