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C-H Activation Reactions Mediated by Pd Based Heterogeneous Catalysts : Regioselective Formation of C-O and C-X Bonds

Majeed, Maitham LU (2018)
Abstract (Swedish)
Katalys är ryggraden i många processer i vardagen. Även människokroppen styrs huvudsakligen av katalysatorer. Detta viktiga koncept tillåter oss att på ett miljövänligt sätt konvertera råmaterial som råolja och naturgas till värdefulla och oersättliga produkter, till exempel motorbränslen, läkemedel och agrokemikalier. En katalysprocess drivs av en katalysator, vilket således är en substans som, utan att förbrukas under processen, gör reaktionen snabbare och mer selektiv genom att förändra reaktionsvägen.
Kolvätebindningar (C-H-bindningar) är bland de mest stabila och oreaktiva kemiska bindningarna och dessa återfinns i hög utsträckning i de flesta kolkällor i naturen, inte minst råolja. Att hitta en miljövänlig väg för att konvertera... (More)
Katalys är ryggraden i många processer i vardagen. Även människokroppen styrs huvudsakligen av katalysatorer. Detta viktiga koncept tillåter oss att på ett miljövänligt sätt konvertera råmaterial som råolja och naturgas till värdefulla och oersättliga produkter, till exempel motorbränslen, läkemedel och agrokemikalier. En katalysprocess drivs av en katalysator, vilket således är en substans som, utan att förbrukas under processen, gör reaktionen snabbare och mer selektiv genom att förändra reaktionsvägen.
Kolvätebindningar (C-H-bindningar) är bland de mest stabila och oreaktiva kemiska bindningarna och dessa återfinns i hög utsträckning i de flesta kolkällor i naturen, inte minst råolja. Att hitta en miljövänlig väg för att konvertera eller klyva C-H-bindningar är en process som brukar kallas C-H aktivering, och denna metod för att producera användbara material har blivit en central frågeställning för organiska kemister under de senaste decennierna. Utveckling av katalysatorer är en av nycklarna för att lösa detta.
I denna avhandling framställdes palladium baserade molekyler som deponerats på bärare för att få heterogena katalysatorer för C-H-aktiveringsreaktioner, som till exempel oxidation och halogenering av arener, vilket är väldigt viktiga transformationer inom läkemedels- och agrokemikalieindustrin. Heterogena katalysatorer kännetecknas av de är lätta att separera från reaktanter och produkter. För att simulera storskaliga applikationer testades dessa katalysatorer också i kontinuerlig flödesproduktion, där de visade sig ha hög aktivitet och stabilitet över tiden.
Avhandlingen uppfyllde framgångsrikt de uppställda målen att syntetisera, tillämpa och förstå dessa katalysatorer.
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Abstract
New classes of N-heterocyclic carbene-palladium(II) complexes containing either a vinyl group in different positions or an anthracene tag in the backbone of the N-heterocycle were synthesized and fully characterized. The vinyl based complexes were copolymerized with divinylbenzene to fabricate robust polymer-supported NHC-Pd(II) systems, while the anthracene based complexes were π-stacked onto the surface of reduced graphene oxide (rGO) producing immobilized catalysts with interesting features. Advanced solid-state characterization techniques focused on the structure and oxidation state of the Pd(II) center of the all the supported complexes and showed the presence of Pd(II) species in the native catalysts without any trace of Pd(0)... (More)
New classes of N-heterocyclic carbene-palladium(II) complexes containing either a vinyl group in different positions or an anthracene tag in the backbone of the N-heterocycle were synthesized and fully characterized. The vinyl based complexes were copolymerized with divinylbenzene to fabricate robust polymer-supported NHC-Pd(II) systems, while the anthracene based complexes were π-stacked onto the surface of reduced graphene oxide (rGO) producing immobilized catalysts with interesting features. Advanced solid-state characterization techniques focused on the structure and oxidation state of the Pd(II) center of the all the supported complexes and showed the presence of Pd(II) species in the native catalysts without any trace of Pd(0) nanoparticles, confirming the success of the preparation pathways. The supported catalysts were applied as heterogeneous catalysts in C-H activation of arenes using different methodologies. In the undirected C-H acetoxylation of simple, methylated, and poly arenes, the supported catalysts showed a similar or superior performance compared to their homogeneous analogues. In addition to that, the polymer based catalysts demonstrated a high catalytic activity and an excellent regioselectivity, up to 100% in many cases, in directed C-H halogenation of arylpyridines. Further advantages of these heterogeneous systems are their high stability and activity, their easy separation and recovery, meaning that they are recyclable for several runs with no leaching of palladium and no loss of activity. Furthermore, the best polymeric catalyst disclosed an exceptional activity and 100% selectivity towards the mono-halogenated product under continuous flow conditions for up to 6 days, during which the original oxidation state of Pd(II) was maintained.
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Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Martín-Matute, Belén, Department of Organic Chemistry, Stockholm University, Sweden
organization
publishing date
type
Thesis
publication status
published
subject
keywords
C-H Activation, N-heterocyclic carbenes, palladium, polymer supported Pd(II)), undirected acetoxylation, directed halogenation, continuous flow, reduced graphene oxide supported Pd(II)
pages
210 pages
publisher
Lund University, Faculty of Science, Department of Chemistry, Centre for Analysis and Synthesis
defense location
Lecture hall F, Center for chemistry and chemical engineering, Naturvetarvägen 14, Lund
defense date
2018-02-02 10:00
ISBN
978-91-7422-560-0
978-91-7422-559-4
language
English
LU publication?
yes
id
bb91179b-2a0e-4d8a-8da2-bf8e3cecf0da
date added to LUP
2018-01-25 09:09:47
date last changed
2018-05-29 11:24:42
@phdthesis{bb91179b-2a0e-4d8a-8da2-bf8e3cecf0da,
  abstract     = {New classes of N-heterocyclic carbene-palladium(II) complexes containing either a vinyl group in different positions or an anthracene tag in the backbone of the N-heterocycle were synthesized and fully characterized. The vinyl based complexes were copolymerized with divinylbenzene to fabricate robust polymer-supported NHC-Pd(II) systems, while the anthracene based complexes were π-stacked onto the surface of reduced graphene oxide (rGO) producing immobilized catalysts with interesting features. Advanced solid-state characterization techniques focused on the structure and oxidation state of the Pd(II) center of the all the supported complexes and showed the presence of Pd(II) species in the native catalysts without any trace of Pd(0) nanoparticles, confirming the success of the preparation pathways. The supported catalysts were applied as heterogeneous catalysts in C-H activation of arenes using different methodologies. In the undirected C-H acetoxylation of simple, methylated, and poly arenes, the supported catalysts showed a similar or superior performance compared to their homogeneous analogues. In addition to that, the polymer based catalysts demonstrated a high catalytic activity and an excellent regioselectivity, up to 100% in many cases, in directed C-H halogenation of arylpyridines. Further advantages of these heterogeneous systems are their high stability and activity, their easy separation and recovery, meaning that they are recyclable for several runs with no leaching of palladium and no loss of activity. Furthermore, the best polymeric catalyst disclosed an exceptional activity and 100% selectivity towards the mono-halogenated product under continuous flow conditions for up to 6 days, during which the original oxidation state of Pd(II) was maintained.  <br/>},
  author       = {Majeed, Maitham},
  isbn         = {978-91-7422-560-0 },
  keyword      = {C-H Activation,N-heterocyclic carbenes,palladium,polymer supported Pd(II)),undirected acetoxylation,directed halogenation,continuous flow,reduced graphene oxide supported Pd(II)},
  language     = {eng},
  pages        = {210},
  publisher    = {Lund University, Faculty of Science, Department of Chemistry, Centre for Analysis and Synthesis},
  school       = {Lund University},
  title        = {C-H Activation Reactions Mediated by Pd Based Heterogeneous Catalysts : Regioselective Formation of C-O and C-X Bonds},
  year         = {2018},
}