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High Valent Metal Oxo Complexes as Oxidation Catalysts

Hossain, Kamal LU (2017)
Abstract (Swedish)
Grundämnena molybden, wolfram och vanadin spelar viktiga roller i biologiska system. De återfinns bl a i ett antal enzymer, där de genomför s k syreöverföringsreaktioner, d v s de tar en syreatom från en molekyl och överför den till en annan molekyl. Sådana reaktioner är av stor vikt i kemi, eftersom införandet av syre i olika molekyler är viktig vid framställning av många kemikalier som kan användas i industrin, inklusive läkemedelsindustrin. I den forskning som behandlas i denna avhandling, har nya komplex av de ovannämnda metallerna framställts och använts som funktionella modeller för sådana biologiska metallenheter (metallenzymer). Med ”funktionella modeller” menas att molekylerna inte nödvändigtvis efterliknar de koordinationsenheter... (More)
Grundämnena molybden, wolfram och vanadin spelar viktiga roller i biologiska system. De återfinns bl a i ett antal enzymer, där de genomför s k syreöverföringsreaktioner, d v s de tar en syreatom från en molekyl och överför den till en annan molekyl. Sådana reaktioner är av stor vikt i kemi, eftersom införandet av syre i olika molekyler är viktig vid framställning av många kemikalier som kan användas i industrin, inklusive läkemedelsindustrin. I den forskning som behandlas i denna avhandling, har nya komplex av de ovannämnda metallerna framställts och använts som funktionella modeller för sådana biologiska metallenheter (metallenzymer). Med ”funktionella modeller” menas att molekylerna inte nödvändigtvis efterliknar de koordinationsenheter som återfinns i enzymerna, men i de molekyler som diskuteras i denna avhandling är syre (i form av en oxidjon, O2-) alltid bunden till metallen, i överensstämmelse med de biologiska enheterna.
De framställda komplexens förmåga att verka som katalysatorer för syreöverföringsreaktioner har undersökts. De katalytiska reaktionerna har utförts på molekyler som är goda modeller för biologiska molekyler som genomgår sådana reaktioner genom att ta emot en syreatom. Syreatomen tas från olika reagens som lätt kan ge ifrån sig syre, och på ett sådant sätt fungera som ett s k oxidationsmedel. I de undersökningar som beskrives i denna avhandling, har väteperoxid, H2O2, använts som en syredonator därför att det är ett relativt miljövänligt oxidationsmedel som ger vatten som en biprodukt. De reaktioner som har studerats är bl a epoxidering, där en syreatom skjuts in i en dubbelbinding mellan två kol, så att en cyklisk enhet innehållande en kol-syre-kol-brygga skapas, samt sulfoxidering, där en syreatom binds till en svavelatom (svaveljon). Dessutom har s k haloperoxideringsreaktioner studerats, där halogener (klor, brom, jod) överförs till en molekyl i en reaktion som involverar väteperoxid. I flera fall har de framställda metallkomplexen visat sig vara dugliga katalysatorer; t ex har några wolframkomplex som har framställts visat sig vara mycket goda katalysatorer för haloperoxidering.
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Abstract
A series of new dioxomolybdenum(VI) and -tungsten(VI) complexes of tripodal tetradentate and tridentate amino bis- and monophenolate ligands have been synthesized and characterized. The majority of the complexes are mononuclear, but dimeric and trimeric oxo-bridged M(VI) (M = Mo, W) were also obtained. The reactivities of all complexes have been investigated in oxygen atom transfer (OAT) processes, e.g. epoxidation and sulfoxidation, with different organic substrates. Good results were obtained for epoxidation of cyclooctene, but low to moderate yields were observed for more challenging substrates (1-octene, styrene, limonene and α-terpineol). The tungsten complexes exhibited very high activity in cyclooctene epoxidation when H2O2 was used... (More)
A series of new dioxomolybdenum(VI) and -tungsten(VI) complexes of tripodal tetradentate and tridentate amino bis- and monophenolate ligands have been synthesized and characterized. The majority of the complexes are mononuclear, but dimeric and trimeric oxo-bridged M(VI) (M = Mo, W) were also obtained. The reactivities of all complexes have been investigated in oxygen atom transfer (OAT) processes, e.g. epoxidation and sulfoxidation, with different organic substrates. Good results were obtained for epoxidation of cyclooctene, but low to moderate yields were observed for more challenging substrates (1-octene, styrene, limonene and α-terpineol). The tungsten complexes exhibited very high activity in cyclooctene epoxidation when H2O2 was used as an oxidant and dimethyl carbonate was used as a solvent. Several molybdenum complexes were found to be good sulfoxidation catalysts, but no activity could be detected for the tungsten complexes that were tested.
For comparative purposes, several new vanadium(V) oxo complexes of amino bis- and monophenolate ligands have been synthesised and investigated as catalysts for the epoxidation and sulfoxidation reactions. The overall catalytic efficiencies were low for epoxidation but excellent for sulfoxidation.
Finally, new oxotungsten(VI) complexes have been prepared from aminobisphenol and aminomonophenol ligands and examined as catalysts for haloperoxidation of various organic substrates, using hydrogen peroxide as oxidant. They showed good catalytic performances for the bromoperoxidation reaction. Some of the more active catalysts were also investigated as chloroperoxidation catalysts; these reactions were more sluggish than the analogous bromination reactions, but the catalytic performances was better than for other reported tungsten catalysts.
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Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Duhme-Klair, Anne-Kathrin, Department of Chemistry, University of York, United Kingdom
organization
publishing date
type
Thesis
publication status
published
subject
keywords
molybdenum, tungsten, Vanadium, oxygen atom transfer, epoxidation, sulfoxidation, molybdenum, tungsten, vanadium, oxygen atom transfer, epoxidation, sulfoxidation
publisher
Lund University, Faculty of Science, Department of Chemistry, Division of Chemical Physics
defense location
Lecture hall G, Center for chemistry and chemical engineering, Naturvetarvägen 14, Lund
defense date
2017-03-07 09:15
ISBN
978-91-7422-502-0
language
English
LU publication?
yes
id
0bcfd29f-849e-4978-939d-df3c05c2025c
date added to LUP
2017-02-02 16:03:19
date last changed
2018-01-17 13:08:41
@phdthesis{0bcfd29f-849e-4978-939d-df3c05c2025c,
  abstract     = {A series of new dioxomolybdenum(VI) and -tungsten(VI) complexes of tripodal tetradentate and tridentate amino bis- and monophenolate ligands have been synthesized and characterized. The majority of the complexes are mononuclear, but dimeric and trimeric oxo-bridged M(VI) (M = Mo, W) were also obtained. The reactivities of all complexes have been investigated in oxygen atom transfer (OAT) processes, e.g. epoxidation and sulfoxidation, with different organic substrates. Good results were obtained for epoxidation of cyclooctene, but low to moderate yields were observed for more challenging substrates (1-octene, styrene, limonene and α-terpineol). The tungsten complexes exhibited very high activity in cyclooctene epoxidation when H2O2 was used as an oxidant and dimethyl carbonate was used as a solvent. Several molybdenum complexes were found to be good sulfoxidation catalysts, but no activity could be detected for the tungsten complexes that were tested.<br/>For comparative purposes, several new vanadium(V) oxo complexes of amino bis- and monophenolate ligands have been synthesised and investigated as catalysts for the epoxidation and sulfoxidation reactions. The overall catalytic efficiencies were low for epoxidation but excellent for sulfoxidation.<br/>Finally, new oxotungsten(VI) complexes have been prepared from aminobisphenol and aminomonophenol ligands and examined as catalysts for haloperoxidation of various organic substrates, using hydrogen peroxide as oxidant. They showed good catalytic performances for the bromoperoxidation reaction. Some of the more active catalysts were also investigated as chloroperoxidation catalysts; these reactions were more sluggish than the analogous bromination reactions, but the catalytic performances was better than for other reported tungsten catalysts.<br/>},
  author       = {Hossain, Kamal},
  isbn         = {978-91-7422-502-0},
  keyword      = {molybdenum,tungsten,Vanadium,oxygen atom transfer,epoxidation,sulfoxidation,molybdenum,tungsten,vanadium,oxygen atom transfer,epoxidation,sulfoxidation},
  language     = {eng},
  publisher    = {Lund University, Faculty of Science, Department of Chemistry, Division of Chemical Physics},
  school       = {Lund University},
  title        = {High Valent Metal Oxo Complexes as Oxidation Catalysts},
  year         = {2017},
}