Reactivity Studies of Boron-Nitrogen Containing Reactive Intermediates Using Matrix Isolation and Computational Tools

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URI: http://hdl.handle.net/10900/158250
http://nbn-resolving.de/urn:nbn:de:bsz:21-dspace-1582508
http://dx.doi.org/10.15496/publikation-99582
http://nbn-resolving.org/urn:nbn:de:bsz:21-dspace-1582506
http://nbn-resolving.org/urn:nbn:de:bsz:21-dspace-1582504
Dokumentart: PhDThesis
Date: 2024-10-14
Language: English
Faculty: 7 Mathematisch-Naturwissenschaftliche Fakultät
Department: Chemie
Advisor: Bettinger, Holger (Prof. Dr.)
Day of Oral Examination: 2024-09-13
DDC Classifikation: 500 - Natural sciences and mathematics
540 - Chemistry and allied sciences
Keywords: Chemie
Other Keywords:
Matrix Isolation
reactive intermediate
computational chemistry
Azaborinine
BN-aryne
License: http://tobias-lib.uni-tuebingen.de/doku/lic_ohne_pod.php?la=de http://tobias-lib.uni-tuebingen.de/doku/lic_ohne_pod.php?la=en
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Inhaltszusammenfassung:

Matrix isolation and computational studies were conducted to explore the reactivity of cyclic iminoboranes, specifically 1,2-azaborinine and 1-(tert-butyldimethylsilyl)-1,3,2-diazaborepine, with various molecules. These studies involved identifying reaction products and investigating potential energy surfaces. The experimental results were supported by computational data obtained by density functional theory (DFT) and ab-initio methods. The computational analysis focusing on the reactivity of 1,2-azaborinine, examined both (2 + 2) and (2 + 4) cycloaddition reactions with organic π-substrates. The results revealed that Lewis acid-base complexes form without an energy barrier, serving as key intermediates in subsequent reactions. Notably, the (2 + 4) cycloaddition was preferred over the (2 + 2) cycloaddition due to favourable symmetry considerations. Additionally, dibenzo derivatives of 1,2-azaborinine were studied to gain insights into their spectroscopic properties and reactivity. 2,4,7,9-tetra-tert-butyldibenzo[c,e][1,2]azaborinine was successfully isolated under cryogenic matrix conditions. Steric hindrance due to tert-butyl groups prevented nitrogen fixation during its generation unlike in the case of dibenzo[c,e][1,2]azaborinine. The impact of ring size on cyclic iminoborane reactivity was further investigated by isolating and characterizing 1-(tert-butyldimethylsilyl)-1,3,2-diazaborepine, a seven-membered cyclic iminoborane. Despite not interacting with dinitrogen, this compound unexpectedly underwent a (2 + 2) cycloaddition reaction with ethene.

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