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Sterically modulated palladium(II)-N-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and DFT studies

The synthesis of a series of sterically modulated palladium(II)-NHC complexes (9-11) of the general formula [Pd(NHC)(2)Cl-2] (NHC = 1-benzyl-3(2'-methyl)-propylbenzimidazol-2-ylidine, 1-benzyl-3 (2'-methyl)-butylbenzimidazol-2-ylidine and 1-benzyl-3-hexylbenzimidazol-2-ylidine) from their...

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Main Authors: Salman, Abbas Washeel, Rehman, Ghani Ur, Abdullah, Norbani, Budagumpi, Srinivasa, Endud, Salasiah, Abdallah, Hassan Hadi, Wong, Wen Yee
Format: Article
Published: Elsevier 2014
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Q Science
Online Access:http://eprints.utm.my/id/eprint/62667/
http://dx.doi.org/10.1016/j.poly.2014.06.054
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spelling my.utm.626672017-06-01T03:01:26Z http://eprints.utm.my/id/eprint/62667/ Sterically modulated palladium(II)-N-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and DFT studies Salman, Abbas Washeel Rehman, Ghani Ur Abdullah, Norbani Budagumpi, Srinivasa Endud, Salasiah Abdallah, Hassan Hadi Wong, Wen Yee Q Science The synthesis of a series of sterically modulated palladium(II)-NHC complexes (9-11) of the general formula [Pd(NHC)(2)Cl-2] (NHC = 1-benzyl-3(2'-methyl)-propylbenzimidazol-2-ylidine, 1-benzyl-3 (2'-methyl)-butylbenzimidazol-2-ylidine and 1-benzyl-3-hexylbenzimidazol-2-ylidine) from their respective silver(I) counterparts (6-8) is presented. Two novel triazine-tethered Zwitterionic (benz) imidazolium salts, 4 and 5, were prepared and tested as NHC precursors for the preparation of silver(I) complexes. However, all our attempts to prepare silver(I) derivatives from salts 4 and 5 ended with negative results due to the low acidity of the C2 protons. The Zwitterionic derivative 4 was additionally characterized by the single crystal X-ray diffraction technique. The molecular structure of 4 evidenced pi-pi stacking interactions between the triazine rings of two crystallographically independent units. The palladium complexes 9-11 showed good catalytic activities in the epoxidation of 1-octene and styrene under homogeneous conditions with aqueous hydrogen peroxide as an oxidant. The effect of temperature and solvent on the epoxidation of the aforementioned olefins using complexes 9-11 was also explored. Density functional theory (DFT) was used to model the structures of the isomers of the palladium complexes. Geometry parameters, electronic energy, molecular orbital energies, band gap, vibrational frequencies and the cis-trans energy barrier were calculated. Elsevier 2014 Article PeerReviewed Salman, Abbas Washeel and Rehman, Ghani Ur and Abdullah, Norbani and Budagumpi, Srinivasa and Endud, Salasiah and Abdallah, Hassan Hadi and Wong, Wen Yee (2014) Sterically modulated palladium(II)-N-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and DFT studies. Polyhedron, 81 . pp. 499-510. ISSN 0277-5387 http://dx.doi.org/10.1016/j.poly.2014.06.054 DOI:10.1016/j.poly.2014.06.054
institution Universiti Teknologi Malaysia
building UTM Library
collection Institutional Repository
continent Asia
country Malaysia
content_provider Universiti Teknologi Malaysia
content_source UTM Institutional Repository
url_provider http://eprints.utm.my/
topic Q Science
spellingShingle Q Science
Salman, Abbas Washeel
Rehman, Ghani Ur
Abdullah, Norbani
Budagumpi, Srinivasa
Endud, Salasiah
Abdallah, Hassan Hadi
Wong, Wen Yee
Sterically modulated palladium(II)-N-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and DFT studies
description The synthesis of a series of sterically modulated palladium(II)-NHC complexes (9-11) of the general formula [Pd(NHC)(2)Cl-2] (NHC = 1-benzyl-3(2'-methyl)-propylbenzimidazol-2-ylidine, 1-benzyl-3 (2'-methyl)-butylbenzimidazol-2-ylidine and 1-benzyl-3-hexylbenzimidazol-2-ylidine) from their respective silver(I) counterparts (6-8) is presented. Two novel triazine-tethered Zwitterionic (benz) imidazolium salts, 4 and 5, were prepared and tested as NHC precursors for the preparation of silver(I) complexes. However, all our attempts to prepare silver(I) derivatives from salts 4 and 5 ended with negative results due to the low acidity of the C2 protons. The Zwitterionic derivative 4 was additionally characterized by the single crystal X-ray diffraction technique. The molecular structure of 4 evidenced pi-pi stacking interactions between the triazine rings of two crystallographically independent units. The palladium complexes 9-11 showed good catalytic activities in the epoxidation of 1-octene and styrene under homogeneous conditions with aqueous hydrogen peroxide as an oxidant. The effect of temperature and solvent on the epoxidation of the aforementioned olefins using complexes 9-11 was also explored. Density functional theory (DFT) was used to model the structures of the isomers of the palladium complexes. Geometry parameters, electronic energy, molecular orbital energies, band gap, vibrational frequencies and the cis-trans energy barrier were calculated.
format Article
author Salman, Abbas Washeel
Rehman, Ghani Ur
Abdullah, Norbani
Budagumpi, Srinivasa
Endud, Salasiah
Abdallah, Hassan Hadi
Wong, Wen Yee
author_facet Salman, Abbas Washeel
Rehman, Ghani Ur
Abdullah, Norbani
Budagumpi, Srinivasa
Endud, Salasiah
Abdallah, Hassan Hadi
Wong, Wen Yee
author_sort Salman, Abbas Washeel
title Sterically modulated palladium(II)-N-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and DFT studies
title_short Sterically modulated palladium(II)-N-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and DFT studies
title_full Sterically modulated palladium(II)-N-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and DFT studies
title_fullStr Sterically modulated palladium(II)-N-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and DFT studies
title_full_unstemmed Sterically modulated palladium(II)-N-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and DFT studies
title_sort sterically modulated palladium(ii)-n-heterocyclic carbene complexes for the catalytic oxidation of olefins: synthesis, crystal structure, characterization and dft studies
publisher Elsevier
publishDate 2014
url http://eprints.utm.my/id/eprint/62667/
http://dx.doi.org/10.1016/j.poly.2014.06.054
_version_ 1643655487491670016
score 13.211869

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