Polymerization of 1,3-Butadiene with Catalysts Based on Cobalt Dichloride Complexes with Aminophosphines: Switching the Regioselectivity by Varying the MAO/Co Molar Ratio

Ricci, Giovanni; Sommazzi, Anna; Masi, Francesco; Forni, Alessandra

doi:10.1007/s10118-023-3060-x

Cited by 1 publication

(1 citation statement)

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“…It was discovered that catalytic systems made up of transition metal complexes like chromium, iron, cobalt, and nickel with phosphorus and nitrogen ligands and methylaluminoxane (MAO) are highly active in 1,3-butadiene polymerization. Moreover, the cis-1,4 microstructure can be optimized by varying both ligands and metals [20][21][22][23][24][25][26][27]. Neodymium-based catalytic systems also show outstanding performance in the cis-1,4 polymerization of 1,3-butadiene.…”

Section: Introductionmentioning

confidence: 99%

Stereoselectivity in Butadiene Polymerization Promoted by Using Ziegler–Natta Catalysts Based on (Anilidomethyl)pyridine Group (IV) Complexes

Milione,

Pragliola

2023

Symmetry

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The stereoselective polymerization of conjugated dienes promoted by using transition metal complexes has attracted much interest in both industrial and academic environments for the relevance of polydienes as synthetic rubbers and for the challenging reaction mechanisms. Among the different transition metal complexes, those based on group IV have been demonstrated to be versatile and efficient catalysts. Titanium complexes are generally more active than zirconium complexes. A rare exception to this trend is represented by a series of Zr(IV) complexes supported by (anilidomethyl)pyridine ligands that, after activation by using Al(iBu2H)/MAO, were found to be highly active affording exclusively cis-1,4-polybutadiene. To rationalize this unexpected trend and to obtain more insights into the parameters that control the reactivity of group IV complexes, a theoretical investigation of the entire polymerization mechanism, employing density functional methods, was undertaken. In the framework of the widely accepted polymerization scheme, the different intermediates featuring h4 (both cis and trans) coordination of the monomer and h1 or h3 (syn or anti)allyl coordination of the growing chain were scrutinized. Subsequently, the effects of the metal center on the free-energy profiles of the elementary steps involved in the reaction were examined. The results presented herein aim to achieve a better knowledge of the influence of the metal on the polymerization rates and on the stereoselectivity of the reaction.

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