DSpace
 

KNUSTSpace >
Conference Proceedings >
College of Science >

Please use this identifier to cite or link to this item: http://hdl.handle.net/123456789/12687

Title: A computational study of the addition of ReO3L (L = Cl−, CH3, OCH3 and Cp) to ethenone
Authors: Aniagyei, Albert
Tia, Richard
Adei, Evans
Keywords: Ketene oxidation
Chemoselectivity
Periselectivity
Metalla-2,4-dioxolane
Issue Date: 22-Mar-2016
Publisher: SpringerPlus
Citation: Aniagyei et al. SpringerPlus (2016) 5:354 DOI 10.1186/s40064-016-2012-0
Abstract: The periselectivity and chemoselectivity of the addition of transition metal oxides of the type ReO3L (L=Cl, CH3, OCH3 and Cp) to ethenone have been explored at the MO6 and B3LYP/LACVP* levels of theory. The activation bar-riers and reaction energies for the stepwise and concerted addition pathways involving multiple spin states have been computed. In the reaction of ReO3L (L=Cl−, OCH3, CH3 and Cp) with ethenone, the concerted [2+2] addi-tion of the metal oxide across the C=C and C=O double bond to form either metalla-2-oxetane-3-one or metalla-2,4-dioxolane is the most kinetically favored over the formation of metalla-2,5-dioxolane-3-one from the direct [3+2] addition pathway. The trends in activation and reaction energies for the formation of metalla-2-oxetane-3-one and metalla-2,4-dioxolane are Cp<Cl−<OCH3<CH3 and Cp<OCH3<CH3<Cl− and for the reaction energies are Cp<OCH3<Cl−<CH3 and Cp<CH3<OCH3<Cl CH3. The concerted [3+2] addition of the metal oxide across the C=C double of the ethenone to form species metalla-2,5-dioxolane-3-one is thermodynamically the most favored for the ligand L=Cp. The direct [2+2] addition pathways leading to the formations of metalla-2-oxetane-3-one and metalla-2,4-dioxolane is thermodynamically the most favored for the ligands L=OCH3 and Cl−. The difference between the calculated [2+2] activation barriers for the addition of the metal oxide LReO3 across the C=C and C=O functionalities of ethenone are small except for the case of L=Cl− and OCH3. The rearrangement of the metalla-2-ox-etane-3-one–metalla-2,5-dioxolane-3-one even though feasible, are unfavorable due to high activation energies of their rate-determining steps. For the rearrangement of the metalla-2-oxetane-3-one to metalla-2,5-dioxolane-3-one, the trends in activation barriers is found to follow the order OCH3<Cl−<CH3<Cp. The trends in the activation ener-gies for the most favorable [2+2] addition pathways for the LReO3–ethenone system is CH3>CH3O−>Cl−>Cp. For the analogous ethylene–LReO3 system, the trends in activation and reaction energies for the most favorable [3+2] addition pathway is CH3>CH3O−>Cl−>Cp [10]. Even though the most favored pathway in the ethylene-LReO3system is the [3+2] addition pathway and that on the LReO3–ethenone is the [2+2] addition pathway, the trends in the activation energies for both pathways are the same, i.e. CH3>CH3O−>Cl−>Cp. However, the trends in reaction energies are quite different due to different product stabilities. The formation of the acetic acid precursor through the direct addition pathways was unsuccessful for all the ligands studied. The formation of the acetic acid precursor through the cyclization of the metalla-2-oxetane-3-one is only possible for the ligands L=Cl−, CH3 whiles for the cyclization of metalla-2-oxetane-4-one to the acetic acid precursor is only possible for the ligand L=CH3. Although there are spin-crossover reaction observed for the ligands L=Cl−, CH3 and CH3O−, the reactions occurring on the single surfaces have been found to occur with lower energies than their spin-crossover counterparts.
Description: An article published Springer Plus and also available at DOI 10.1186/s40064-016-2012-0
URI: http://hdl.handle.net/123456789/12687
Appears in Collections:College of Science

Files in This Item:

File Description SizeFormat
s40064-016-2012-02.19 MBAdobe PDFView/Open

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

 

Valid XHTML 1.0! DSpace Software Copyright © 2002-2010  Duraspace - Feedback