The potential energy surfaces of the initial reactions of ethylene insertion for the Ziegler-Natta catalysis with bridging groups of Cp ligands were studied by ab initio MO and density functional methods. Three metals (Ti, Zr, and Hf) in the Zeigler-Natta catalysis and eight bridging groups (BH, CH 2 , NH, O, AlH, SiH 2 , PH, and S) were treated. For the complex formation between ethylene and metallocenes, two type structures (vertical and horizon) were found. The vertical type structures are more stable in energy than the horizon types. The formation energy of the complex between ethylene and the metallocenes by incorporation of bridging atom or group is related to the geometrical hindrance and the bond interaction as shown in the case of boron bridging system.

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A novel mechanism for the polymerization of butadiene by cationic gadolinium metallocene in the presence of excess Al(iBu)3 is presented. The absence of an initial Gd‐alkyl bond in this reaction system precludes the conventional mechanism by coordinative chain transfer polymerization (CCTP). Density functional theory (DFT) analysis indicates a mechanism in which cationic Gd assists butadiene insertion into one of the Al–C bonds of Al(iBu)3, explaining the 1,4‐cis selectivity unique to this catalytic system. More information can be found in the Research Article by Rika Fukushima et al.

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.