Comparison of Pincer-Ligated Iridium Complexes with Different Electronic Properties in Acceptorless Dehydrogenation of 1-Phenylethanol
(2023) KEML10 20231Department of Chemistry
- Abstract
- Four pincer-ligated iridium complexes, 1-4, featuring substituents with different electronic properties on meta and para positions on the aromatic backbone were synthesized for the purpose of comparing their efficiency as catalysts in the acceptorless dehydrogenation of 1-phenylethanol. Previous studies have already revealed that turnover frequencies were higher in more dilute catalyst solutions, but the interesting new observation in this project is that this also applies to these four complexes. We obtained concentration- and temperature-dependent plot by conducting an initial rate experiment over a 15-minute period. These were then used to determine the reaction orders and activation parameters for these four catalysts. Regarding the... (More)
- Four pincer-ligated iridium complexes, 1-4, featuring substituents with different electronic properties on meta and para positions on the aromatic backbone were synthesized for the purpose of comparing their efficiency as catalysts in the acceptorless dehydrogenation of 1-phenylethanol. Previous studies have already revealed that turnover frequencies were higher in more dilute catalyst solutions, but the interesting new observation in this project is that this also applies to these four complexes. We obtained concentration- and temperature-dependent plot by conducting an initial rate experiment over a 15-minute period. These were then used to determine the reaction orders and activation parameters for these four catalysts. Regarding the reaction orders for the four catalysts, the catalyst dependence is non-proportional. With higher catalyst concentrations a diminishing return occurs. This could be due to hydrogen in the solution, which could affect the catalyst performance. The low enthalpy barrier for the four catalysts shows that minimal bond breaking occurs in the rate-determining step which aligns with the mass transfer of hydrogen. This means that the efficiency of hydrogen leaving the solution can have an impact on the reaction. Based on the experiment over an extended period, both complexes 1 and 2 were very effective in the acceptorless dehydrogenation of 1-phenylethanol and could achieve complete conversion, whereas the catalysts 3 and 4, lose their effectiveness over extended periods. (Less)
- Popular Abstract (Swedish)
- På grund av klimatkrisen och de minskade resurserna av fossila bränslen, accelereras sökandet efter gröna och förnybara energikällor. Vätgas är en av de bästa ersättningarna för fossila bränslen eftersom det enda biprodukten vi får vid förbränning är vatten. Dock är dess användning begränsad på grund av utmaningarna med att lagra och transportera vätgas. Den nya och framväxande teknologin för att lagra och transportera vätgas i flytande material, där de lätt kan extraheras, kallas flytande organiska vätgasbärare (LOHC). För att extrahera vätgas från dessa LOHC används vanligtvis iridiumbaserade katalysatorer. För att förbättra de katalytiska egenskaperna hos dessa katalysatorer behöver vi en djupare förståelse av denna process. Därför... (More)
- På grund av klimatkrisen och de minskade resurserna av fossila bränslen, accelereras sökandet efter gröna och förnybara energikällor. Vätgas är en av de bästa ersättningarna för fossila bränslen eftersom det enda biprodukten vi får vid förbränning är vatten. Dock är dess användning begränsad på grund av utmaningarna med att lagra och transportera vätgas. Den nya och framväxande teknologin för att lagra och transportera vätgas i flytande material, där de lätt kan extraheras, kallas flytande organiska vätgasbärare (LOHC). För att extrahera vätgas från dessa LOHC används vanligtvis iridiumbaserade katalysatorer. För att förbättra de katalytiska egenskaperna hos dessa katalysatorer behöver vi en djupare förståelse av denna process. Därför valde vi fyra komplex som skiljer sig åt i de elektroniska egenskaperna hos liganden och studerade skillnaden i reaktiviteten mellan dem. Resultaten visar att en specifik typ av elektrondragande ligand förbättrar aktiviteten, medan andra resulterar i ogynnsamma effekter. Dessutom gynnas reaktionen för extraktion av vätgas av en effektiv borttagning av bildad vätgas från reaktionssystemet. Denna studie ger en grundläggande förståelse av dessa processer, men ytterligare arbete behövs för att få mer kunskap. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9128119
- author
- Karim, Samer LU
- supervisor
- organization
- course
- KEML10 20231
- year
- 2023
- type
- M2 - Bachelor Degree
- subject
- keywords
- Acceptorless dehydrogenation of alcohols (AAD), Hydrogen mass transfer rate, POCOP pincer ligands, POCOP pincer iridium complexes, Turnover frequencies (TOFs), Analytical chemistry
- language
- English
- id
- 9128119
- date added to LUP
- 2023-06-22 11:00:14
- date last changed
- 2023-06-22 11:00:14
@misc{9128119,
abstract = {{Four pincer-ligated iridium complexes, 1-4, featuring substituents with different electronic properties on meta and para positions on the aromatic backbone were synthesized for the purpose of comparing their efficiency as catalysts in the acceptorless dehydrogenation of 1-phenylethanol. Previous studies have already revealed that turnover frequencies were higher in more dilute catalyst solutions, but the interesting new observation in this project is that this also applies to these four complexes. We obtained concentration- and temperature-dependent plot by conducting an initial rate experiment over a 15-minute period. These were then used to determine the reaction orders and activation parameters for these four catalysts. Regarding the reaction orders for the four catalysts, the catalyst dependence is non-proportional. With higher catalyst concentrations a diminishing return occurs. This could be due to hydrogen in the solution, which could affect the catalyst performance. The low enthalpy barrier for the four catalysts shows that minimal bond breaking occurs in the rate-determining step which aligns with the mass transfer of hydrogen. This means that the efficiency of hydrogen leaving the solution can have an impact on the reaction. Based on the experiment over an extended period, both complexes 1 and 2 were very effective in the acceptorless dehydrogenation of 1-phenylethanol and could achieve complete conversion, whereas the catalysts 3 and 4, lose their effectiveness over extended periods.}},
author = {{Karim, Samer}},
language = {{eng}},
note = {{Student Paper}},
title = {{Comparison of Pincer-Ligated Iridium Complexes with Different Electronic Properties in Acceptorless Dehydrogenation of 1-Phenylethanol}},
year = {{2023}},
}