The effect of the central donor in bis(benzimidazole)-based cobalt catalysts for the selective cis-1,4-polymerisation of butadiene

Abstract

A series of bis(benzimidazole)-based cobalt(II) dichloride complexes containing a range of different central donors has been synthesized and characterized. The nature of the central donor affects the binding of the ligand to the cobalt centre and determines the coordination geometry of the metal complexes. All complexes have been shown to catalyse the polymerization of butadiene, in combination with MAO as the co-catalyst, to give cis-1,4-polybutadiene with high selectivity. The nature of the central donor has a marked influence on the polymerization activity of the catalysts, but does not affect the polymer microstructure. The addition of PPh(3) generally increases the polymerization activity of these cobalt catalysts and results in predominantly (60-70%) 1,2-vinyl-polybutadiene.

Iminopyridine-Based Cobalt(II) and Nickel(II) Complexes: Synthesis, Characterization, and Their Catalytic Behaviors for 1,3-Butadiene Polymerization

“…These results could be explained by the idea that the electron-withdrawing group (Br) at the 6-position reduces the electron density of central metal, and the increased Lewis acidic character facilitates the coordination of 1,3-butadiene molecule, leading to the increment of chain propagation rate. Moreover, due to the electron-contributing and steric hindrance of the CH 3 group, the coordination reaction between 1,3-butadiene and the cobalt center was retarded [10] . The CH 3 group can serve to raise polymer molecular weight (4a, 31.5ˆ10 4 ; 5a, 33.8ˆ10 4 ) and regulate molecular weight distribution (4a, 1.9; 5a, 1.7), suggesting that electron-contributing substituent at 6-position of the pyridine ring retard chain transfer reaction to some extent.…”

“…In order to gain better control over molecular weight, molecular weight distribution, and, more importantly, stereoselectivity of the polymerization, academic and industrial research has focused on well-defined organometallic single-site catalysts. For example, four-coordinated (salen)cobalt(II) ([ONNO] 2´) [7] and bis(salicylaldiminate)cobalt(II) [8], three-coordinated bis(imino)pyridine cobalt (II) [9], bis(benzimidazolyl)amine cobalt (II) [10], bis(benzimidazolyl) pyridine [11,12] cobalt(II), bis(thiazolinyl)pyridine cobalt(II) [13], 2-arylimino-6-(alcohol)pyridine/2-arylamino-6-(alcohol) pyridine cobalt(II) [14], and 3-aryliminomethyl-2-hydroxybenzaldehyde cobalt(II) [15] exhibited high activity and high cis-1,4 selectivity in 1,3-butadiene polymerization in combination with MAO or EASC. The nickel-based catalysts are also of particular interest in the production of high cis-1,4-PBD.…”

Synthesis, characterization and evaluation of porous polybenzimidazole materials for CO2 adsorption at high pressures

“…Peak at around 3616 cm correspond to the O-H stretching which may be attributed to the presence of water in the sample since PBI is a hygroscopic materials and has high affinity for water molecules. It must be noted that two consecutive peaks at 2341 and 2360 cm -1 represent the well complex nature and stretching mode of PBI, which is more prominent in case of PBI-1 (Cariou et al 2010). These two peaks at 2341 and 2360 cm -1 may also indicate trace amount of physisorption of ambient CO 2 .…”

Synthesis of mixed-ligand cobalt complexes and their applications in high cis-1,4-selective butadiene polymerization

“…The development of catalysts plays an important role for efficient control in chain architectures such as stereochemistry, functionality and chain length in polybutadiene synthesis [1][2][3][4][5][6]. Recently, tri-dentated pincer ligands have emerged as attractive auxiliary ligands in iron and cobalt based catalysts promoted for olefin and diene polymerizations [7,8].…”