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Synthesis of amine-functionalized bis(imidazolium)borate salts: novel bis(carbene)borate ligand precursors
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Karagiannis, Ageliki. Synthesis of amine-functionalized bis(imidazolium)borate salts: novel bis(carbene)borate ligand precursors. Retrieved from https://doi.org/doi:10.7282/t3-epev-0c12

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TitleSynthesis of amine-functionalized bis(imidazolium)borate salts: novel bis(carbene)borate ligand precursors
NameKaragiannis, Ageliki (author); Jaekle, Frieder (chair); Prokopchuk, Demyan (internal member); Lockard, Jenny (internal member); Rutgers University; Graduate School - Newark
Date Created2020
Other Date2020-05 (degree)
SubjectBis(imidazolium)borate salts, Chemistry
Extent1 online resource (viii, 44 pages)
DescriptionN-heterocyclic carbenes (NHCs), commonly derived from N,N’-disubstituted imidazolium salts, have gained popularity since their isolation by Arduengo in 1991 and their application as ligands for catalysis by Herrmann in the mid-1990s. An underexplored area of research is the examination of chelating ligands incorporating amine-functionalized bis(NHC) ligands. This thesis focuses on the synthesis of novel bis(imidazolium) borate salts and the preliminary formation of their NHCs. Early attempts of reacting imidazoles with chlorobis(amino)borane reagents yielded incomplete reactions or decomposition, which are likely the consequence of a steric and/or electronic mismatch between boron and its attached amines. After testing several chloroaminoborane reagents, two novel amine-functionalized bis(imidazolium)borate salts have been successfully synthesized and characterized. By reacting 1-tert-butylimidazole (tBuIm) or 1-methylimidazole (MeIm) with iPr2N(Ph)BCl at room temperature, the salts [iPr2NB(Ph)(tBuIm)2][OTf] and [iPr2NB(Ph)(MeIm)2][OTf] (OTf = trifluroomethanesulfonate) can be prepared using a two-step, one-pot synthetic protocol. Halide abstraction using AgOTf to form the proposed intermediate iPr2NB(Ph)OTf, followed by imidazole addition readily produces the target imidazolium borate salts. Optimization efforts resulted in the discovery of a solvent-dependent mechanism in CH3CN versus CH2Cl2 during addition of AgOTf to iPr2NB(Ph)Cl. In both solvents, the desired product is obtained, however the coordinating effects of CH3CN may play a role in minimizing undesirable product formation. Overall, a reliable synthetic method to obtain amine-functionalized bis(imidazolium)borate salts is presented. Preliminary data suggests that deprotonation leads to carbene formation, however more experiments are needed to fully characterize the product. This work holds promise to prepare novel bis(carbene)aminoborates as proton-responsive ligands for electrocatalytic H2 oxidation/production.
NoteM.S.
NoteIncludes bibliographical references
Genretheses, ETD graduate
Persistent URLhttps://doi.org/doi:10.7282/t3-epev-0c12
LanguageEnglish
CollectionGraduate School - Newark Electronic Theses and Dissertations
Organization NameRutgers, The State University of New Jersey
RightsThe author owns the copyright to this work.
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