Ancillary ligand effects on α-olefin polymerization catalyzed by zirconium metallocene: a computational study

Abstract

The polymerization of α-olefins catalyzed by zirconium metallocene catalyst was systematically studied through experiments and density functional theory (DFT) calculations.

Metal–ring interactions in group 2 ansa-metallocenes: assessed with the local vibrational mode theory

“…Metallocenes have received considerable attention for their varied applications in catalysis, materials science, and organic synthesis. 1–5 These sandwich-like π-complexes are typically composed of transition metal d-block elements, although s- and p-block elements can also be used. 6–9 The alteration of metallocenes to have an inter-linkage of two cyclopentadienyl (Cp) ligands forms a unique bridging motif, affecting the overall reactivity and electronic properties and resulting in so-called ansa -metallocenes, which are also known as metallocenophanes.…”

Metallocenes and Beyond for Propene Polymerization: Energy Decomposition of Density Functional Computations Unravels the Different Interplay of Stereoelectronic Effects

“…We anticipate that, while thermal and solvent effects are in some cases not negligible, all the general trends of the results are captured by Δ E values and can be, therefore, analyzed by the ASM-NEDA model. Successful applications of the Bickelhaupt approach in the field of organometallic chemistry have been reported, but, to the best of our knowledge, no systematic studies of olefin polymerization catalyzed by TMs and/or stereoselective propene polymerization have been performed till now. − The integrated DFT/% V Bur /ASM-NEDA strategy turned out to offer a powerful tool for a better understanding of polymerization mechanisms at a molecular level disclosing the subtle differences of C 1 -symmetry active species with nonmetallocene and ansa -metallocene ligands for propene polymerization. For the sake of readability, we separated the Results and Discussion section in two parts: in the first one, we discuss the polymerization mechanisms, whereas in the second part, we analyze the implications of these mechanisms on propene stereoselectivity also including the counterion in the DFT calculations.…”

Unconventional Stereoerror Formation Mechanisms in Nonmetallocene Propene Polymerization Systems Revealed by DFT Calculations

“… 24 , 25 The DFT computational approach has been already tested in propene polymerization catalysis and found to be reliable, 26 , 27 and in the ASM model, 24 , 25 the relative energy of a molecular system is partitioned into the sum of the energies required to distort the reactants into the geometries required to react and into the strength of their mutual interaction. 28 , 29 …”

“…The latter aspect is remarkable because the R 3 “stereodirecting role” has been proposed as the main factor for explaining the stereoselectivity of octahedral complexes (both in homogeneous and heterogeneous phases) − (Figure S1). So, we decided to investigate in more detail the propene polymerization mechanisms of the Zr/Hf salalen catalysts shown in Scheme , using DFT calculations (see Computational Methods) combined with the Activation Strain Model (ASM). , The DFT computational approach has been already tested in propene polymerization catalysis and found to be reliable, , and in the ASM model, , the relative energy of a molecular system is partitioned into the sum of the energies required to distort the reactants into the geometries required to react and into the strength of their mutual interaction. , …”

“…24,25 The DFT computational approach has been already tested in propene polymerization catalysis and found to be reliable, 26,27 and in the ASM model, 24,25 the relative energy of a molecular system is partitioned into the sum of the energies required to distort the reactants into the geometries required to react and into the strength of their mutual interaction. 28,29 ■ COMPUTATIONAL METHODS All DFT static calculations have been performed with the Gaussian09 and Gaussian16 set of programs, 30 using the B3LYP functional of Becke and Perdew. 31,32 The electronic configuration of the molecular systems was described with the standard split-valence basis set with a polarization function of Ahlrichs and co-workers for H, C, N, O, and Cl (SVP).…”