Correlation between regioselectivity and site charge in propene polymerisation catalysed by metallocene

“…One d-polarization function (exponent of 0.284) was augmented for the basis set of Si atoms [55]. Such a computational strategy has been widely used for the study of transition metal-containing systems [56][57][58][59][60][61]. The transition states were ascertained by a single imaginary frequency for the correct mode.…”

Section: Computational Detailsmentioning

confidence: 99%

Computational Studies on the Selective Polymerization of Lactide Catalyzed by Bifunctional Yttrium NHC Catalyst

et al. 2017

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Abstract:A theoretical investigation of the ring-opening polymerization (ROP) mechanism of rac-lactide (LA) with an yttrium complex featuring a N-heterocyclic carbine (NHC) tethered moiety is reported. It was found that the carbonyl of lactide is attacked by N(SiMe 3 ) 2 group rather than NHC species at the chain initiation step. The polymerization selectivity was further investigated via two consecutive insertions of lactide monomer molecules. The insertion of the second monomer in different assembly modes indicated that the steric interactions between the last enchained monomer unit and the incoming monomer together with the repulsion between the incoming monomer and the ligand framework are the primary factors determining the stereoselectivity. The interaction energy between the monomer and the metal center could also play an important role in the stereocontrol.

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“…This trend is unwelcome, though inevitable, and can often result in superficial research. With the contents of the present article, we seek to demonstrate that it is rewarding to do research in traditional fields because there is still room for innovation and improvement, as well as at the frontiers of science because sometimes excellent research can result from scientists intrigued by fundamental knowledge , , even those at undergraduate level , .…”

Section: Discussionmentioning

confidence: 99%

A New Method for Obtaining Russell−Saunders Terms

Liu

2010

J. Chem. Educ.

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Many familiar concepts deserve reconsideration (1). We report a novel method to solve the fundamental problem of determining atomic spectral terms. Atomic spectral terms are of fundamental importance in the investigation of atomic structure. The usual methods are categorized as (a) the determinant-wave function method that involves establishing the eigenfunctions of the Russell-Saunders (R-S) terms, (b) the electronic-arrangement method (2) that involves explicitly writing down all possible microstates of a configuration, (c) the spin-factor method (3-5) in which the spin multiplets are classified by the number of unpaired electrons, and (d) the partial-term method in which the R-S partial terms of R and β spins are used to derive the R-S terms of a given configuration for atoms or molecules (6, 7). Other methods that are less well-known include that of Tuttle (8), which involves establishing a set of rules to guarantee that each adopted quantum number set is allowed by the Pauli principle and occurs only once, and that of Curl and Kilpatrick (9) who employ a method for generating functions to obtain the proper term symbols from a given configuration. Readers who are interested in those methods are directed to the original literature.We report a novel but simple method that shares some common features with those methods that determine molecular electronic terms, especially those that determine the splitting of S, P, D terms in weak ligand fields and of s, p, d orbitals in strong ligand. The innovative feature of this new method is the decomposition of an atomic configuration to R-S terms. But its application in identifying R-S terms has not been reported previously to our knowledge. The new method for determining atomic terms also adopts the same principles used in molecular systems for ruling out impossible microstates for equivalent electron configurations. It is significantly different but complementary to previously published methods for obtaining atomic terms. It shows students that creative thought is worthwhile even in well-developed traditional fields and that applying methods that have already been used in one field can be particularly useful.

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Correlation between regioselectivity and site charge in propene polymerisation catalysed by metallocene

Cited by 17 publications

References 17 publications

Preparation and magnetic properties of barium ferrites substituted with manganese, cobalt, and tin

Preparation and magnetic properties of barium ferrites substituted with manganese, cobalt, and tin

Computational Studies on the Selective Polymerization of Lactide Catalyzed by Bifunctional Yttrium NHC Catalyst

A New Method for Obtaining Russell−Saunders Terms

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