Non‐π‐Allyl Mechanism for the 1,4‐cis‐Butadiene Polymerization: Theoretical Study of Polymerization via Insertion of Butadiene into Al−C Bond with Cationic Gadolinium Metallocene.

This paper reports a computational study on the specific 1,4‐cis polymerization of butadiene catalyzed by the cationic gadolinium metallocene [(C5Me5)2Gd][B(C6F5)4] combined with excess amount of Al(iBu)3. Because this reaction system has no initial Gd–alkyl bond, a mechanism with conventional coordinative chain transfer polymerization (CCTP) is not feasible. Density functional theory (DFT) analyses indicate a novel mechanism in which the cationic Gd plays a crucial role by assisting butadiene insertion into one of the Al−C bond of Al(iBu)3. The proposed butadiene polymerization mechanism can account for the specific 1,4‐cis selectivity of this catalyst system. [ABSTRACT FROM AUTHOR]