Synthesis of palladium(II)-N-heterocyclic carbene via transmetaliation of silver(I) complex and its catalytic activity in epoxidation of alkene
A series of new silver(I)- and palladium(II)-N-heterocyclic carbene complexes of 1-benzyl-3-ethylbenzimidazolium iodide, 1-benzyl-3-(2’-nitrilebenzyl)benzimidazole bromide, 1-benzyl-3-(2’-methyl)propylbenzimidazolium bromide, 1-benzyl-(3’-methyl)butylbenzimidazolium bromide, 1-benzyl-3-hexylbenzimid...
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my-utm-ep.488562020-07-01T07:22:36Z Synthesis of palladium(II)-N-heterocyclic carbene via transmetaliation of silver(I) complex and its catalytic activity in epoxidation of alkene 2014-07 Rehman, Ghani Ur QD Chemistry A series of new silver(I)- and palladium(II)-N-heterocyclic carbene complexes of 1-benzyl-3-ethylbenzimidazolium iodide, 1-benzyl-3-(2’-nitrilebenzyl)benzimidazole bromide, 1-benzyl-3-(2’-methyl)propylbenzimidazolium bromide, 1-benzyl-(3’-methyl)butylbenzimidazolium bromide, 1-benzyl-3-hexylbenzimidazolium bromide were successfully synthesized. The respective N-heterocyclic carbene (NHC) precursors were prepared by the reaction of 1-benzylbenzimidazole with ethyl iodide, 2-bromomethylbenzonitrile, 2-methylpropylbromide, 3-methylbutyl bromide, and n-hexyl bromide in dioxane at C90? . Further, these halide salts were converted into their hexafluorophosphate counterparts by the salt metathesis reaction using KPF6 in methanol. Bis-NHC silver(I) complexes having hexafluorophosphate counterion were yielded (48.4-67.2%) by the reaction of NHC precursors with silver(I) oxide in acetonitrile/methanol at room temperature. Subsequent reactions of the silver(I) hexafluorophosphate complexes with [PdCl2(CNCH3)2] in dichloromethane/methanol afforded the bis-NHC palladium(II) complexes in good yield (48.3-76.4%) via carbene transfer method. All new complexes were fully characterized by various techniques such as CHN analysis, single crystal X-ray diffraction and spectroscopic methods such as FTIR and 1H and 13C NMR. Additionally, in case of silver(I) complex, the bis-[1-benzyl-3-(2’-nitrilebenzyl)benzimidazole] silver(I) hexafluorophosphate was characterized by single crystal X-ray diffraction technique. Preliminary catalytic studies show that the nitrile-functionalized palladium(II)-NHC complex is highly active in the oxidation of 1-octene as well as styrene in aqueous hydrogen peroxide as oxidizing agent at C70? . All the palladium(II) complexes oxidized both the aforementioned olefins efficiently to their corresponding oxidized products with 47 to 58% conversions. However, selectivity towards epoxy products was relatively low in the range of 7-10%. Major product in the oxidation of 1-octene was the 1,2-octanediol, while 2-octanone is the minor product. 2014-07 Thesis http://eprints.utm.my/id/eprint/48856/ http://eprints.utm.my/id/eprint/48856/25/GhaniUrRehmanMFS2014.pdf application/pdf en public http://dms.library.utm.my:8080/vital/access/manager/Repository/vital:85307 masters Universiti Teknologi Malaysia, Faculty of Science Faculty of Science |
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QD Chemistry Rehman, Ghani Ur Synthesis of palladium(II)-N-heterocyclic carbene via transmetaliation of silver(I) complex and its catalytic activity in epoxidation of alkene |
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A series of new silver(I)- and palladium(II)-N-heterocyclic carbene complexes of 1-benzyl-3-ethylbenzimidazolium iodide, 1-benzyl-3-(2’-nitrilebenzyl)benzimidazole bromide, 1-benzyl-3-(2’-methyl)propylbenzimidazolium bromide, 1-benzyl-(3’-methyl)butylbenzimidazolium bromide, 1-benzyl-3-hexylbenzimidazolium bromide were successfully synthesized. The respective N-heterocyclic carbene (NHC) precursors were prepared by the reaction of 1-benzylbenzimidazole with ethyl iodide, 2-bromomethylbenzonitrile, 2-methylpropylbromide, 3-methylbutyl bromide, and n-hexyl bromide in dioxane at C90? . Further, these halide salts were converted into their hexafluorophosphate counterparts by the salt metathesis reaction using KPF6 in methanol. Bis-NHC silver(I) complexes having hexafluorophosphate counterion were yielded (48.4-67.2%) by the reaction of NHC precursors with silver(I) oxide in acetonitrile/methanol at room temperature. Subsequent reactions of the silver(I) hexafluorophosphate complexes with [PdCl2(CNCH3)2] in dichloromethane/methanol afforded the bis-NHC palladium(II) complexes in good yield (48.3-76.4%) via carbene transfer method. All new complexes were fully characterized by various techniques such as CHN analysis, single crystal X-ray diffraction and spectroscopic methods such as FTIR and 1H and 13C NMR. Additionally, in case of silver(I) complex, the bis-[1-benzyl-3-(2’-nitrilebenzyl)benzimidazole] silver(I) hexafluorophosphate was characterized by single crystal X-ray diffraction technique. Preliminary catalytic studies show that the nitrile-functionalized palladium(II)-NHC complex is highly active in the oxidation of 1-octene as well as styrene in aqueous hydrogen peroxide as oxidizing agent at C70? . All the palladium(II) complexes oxidized both the aforementioned olefins efficiently to their corresponding oxidized products with 47 to 58% conversions. However, selectivity towards epoxy products was relatively low in the range of 7-10%. Major product in the oxidation of 1-octene was the 1,2-octanediol, while 2-octanone is the minor product. |
format |
Thesis |
qualification_level |
Master's degree |
author |
Rehman, Ghani Ur |
author_facet |
Rehman, Ghani Ur |
author_sort |
Rehman, Ghani Ur |
title |
Synthesis of palladium(II)-N-heterocyclic carbene via transmetaliation of silver(I) complex and its catalytic activity in epoxidation of alkene |
title_short |
Synthesis of palladium(II)-N-heterocyclic carbene via transmetaliation of silver(I) complex and its catalytic activity in epoxidation of alkene |
title_full |
Synthesis of palladium(II)-N-heterocyclic carbene via transmetaliation of silver(I) complex and its catalytic activity in epoxidation of alkene |
title_fullStr |
Synthesis of palladium(II)-N-heterocyclic carbene via transmetaliation of silver(I) complex and its catalytic activity in epoxidation of alkene |
title_full_unstemmed |
Synthesis of palladium(II)-N-heterocyclic carbene via transmetaliation of silver(I) complex and its catalytic activity in epoxidation of alkene |
title_sort |
synthesis of palladium(ii)-n-heterocyclic carbene via transmetaliation of silver(i) complex and its catalytic activity in epoxidation of alkene |
granting_institution |
Universiti Teknologi Malaysia, Faculty of Science |
granting_department |
Faculty of Science |
publishDate |
2014 |
url |
http://eprints.utm.my/id/eprint/48856/25/GhaniUrRehmanMFS2014.pdf |
_version_ |
1747817488435904512 |