A theoretical study of the insertion of olefins into Timethyl bonds by “Paired Interacting Orbitals”

Shiga, Akinobu; Kawamura, Hiroshi; Ebara, Takeshi; Sasaki, Tomohiro; Kikuzono, Yasuo

doi:10.1016/0022-328x(89)87319-x

Cited by 33 publications

(8 citation statements)

References 7 publications

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“…Theoretical studies, however, have been rarely carried out on styrene polymerization, whereas olefin polymerization has been extensively studied with theoretical calculations. − Moreover, the theoretical studies on the styrene polymerization have been focused only on the stereoselectivity rather than the regioselectivity of styrene insertion. The regioselectivity of metallocene-based styrene polymerization is referred to as the preference of formation of one chemical bond (e.g., secondary insertion in Scheme 1) over that of the other possible chemical bond (e.g., primary insertion in Scheme 1).…”

Section: Introductionmentioning

confidence: 99%

Density Functional Study on the Regioselectivity of Styrene Polymerization with an ansa-Metallocene Catalyst

Yang

Huh

2006

Organometallics

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The mechanism of regioselectivity of styrene polymerization with a Cp-based ansa-matallocene catalyst (Cp = η5-C5H5) was investigated using density functional theory (DFT). The metallocene catalyst studied in this work, (CH3)2SiCp2Ti(CH3)2, is known to produce polystyrene via the secondary insertion of styrene. A cationic species, SiH2Cp2Ti+−CH3, is used as an activated form of the catalyst for modeling the initiation of styrene polymerization. The results show that primary insertion is more favorable than secondary insertion in the initiation of styrene polymerization, and the most stable product obtained from primary insertion blocks an additional primary insertion of styrene monomer. For propagation of styrene polymerization, secondary insertion is more favorable than primary insertion. If primary insertion occurs during the propagation, the most stable product of the primary insertion blocks again the additional primary insertion of styrene and thus enhances the secondary insertion. The main driving force blocking the primary insertion is the repulsive interaction between two phenyl rings of the preinserted styrene and the next approaching styrene.

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Section: Introductionmentioning

confidence: 99%

Density Functional Study on the Regioselectivity of Styrene Polymerization with an ansa-Metallocene Catalyst

Yang

Huh

2006

Organometallics

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“…The metallocene catalysts have several desirable properties such as high activity, an ability to produce high-molecular-weight polymers with a narrow molecular-weight distribution and a potential for rigorous control of stereoselectivity by tailoring metallocene ligands. − Such fascinating properties of the metallocene catalyst have invited a large number of experimental − and theoretical − studies on the metallocene-based polymerization. Although those studies have contributed to understanding of the mechanism of monomer insertion into an active site of the catalytic species in the polymerization to some extent, the mechanism of monomer insertion has not been clearly understood, because the true active catalytic species in the polymerization has not been fully elucidated.…”

Section: Introductionmentioning

confidence: 99%

Effect of Solvent Polarity on the Initiation and the Propagation of Ethylene Polymerization with Constrained Geometry Catalyst/MAO Catalytic System: A Density Functional Study with the Conductor-Like Screening Model

Yang

Huh

2005

Macromolecules

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The effect of solvent polarity on the initiation and propagation of ethylene polymerization with a constrained geometry catalyst (CGC) and MAO counterion was investigated by the density functional theory (DFT) with the conductor-like screening model (COSMO). Structures and energetics of reactant, π-complex, transition state, γ-agostic product, and β-agostic product during insertion of ethylene monomer into the catalytic active species of ionic pair or cationic catalyst are analyzed using the software DMol3. A comparative analysis on the energetics of the ethylene insertion in the gas state and in solvents with different dielectric constants (ε) shows that the solvent polarity affects the energetics of monomer insertion very differently depending upon the model for active catalytic species and/or polymerization stage. This different behavior provides a very useful method for identifying the real active catalytic species in experiment. The two important features of molecular structure determining the dependency of enegetics on the solvent polarity are the degree of exposure of the Ti atom on the solvent medium and the degree of separation of ionic pair during monomer insertion.

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“…Although this analysis was proposed originally for ab initio calculations, we reported that this approach was useful also in analyzing the results of extended Hückel MO calcula- tions [5][6][7]. PIO calculations were carried out on LUMMOX TM system [8,9].…”

Section: Pio Calculationmentioning

confidence: 99%

A theoretical study on Brønsted acidity of WO3 clusters supported on metal oxide supports by “paired interacting orbitals” (PIO) analysis

Shiga¹,

Katada²,

Niwa³

2006

Catalysis Today

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A theoretical study of the insertion of olefins into Timethyl bonds by “Paired Interacting Orbitals”

Cited by 33 publications

References 7 publications

Density Functional Study on the Regioselectivity of Styrene Polymerization with an ansa-Metallocene Catalyst

Density Functional Study on the Regioselectivity of Styrene Polymerization with an ansa-Metallocene Catalyst

Effect of Solvent Polarity on the Initiation and the Propagation of Ethylene Polymerization with Constrained Geometry Catalyst/MAO Catalytic System: A Density Functional Study with the Conductor-Like Screening Model

A theoretical study on Brønsted acidity of WO3 clusters supported on metal oxide supports by “paired interacting orbitals” (PIO) analysis

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