Optimizacija sinteze mezoionskega paladijevega(II) kompleksa
Namen magistrskega dela je bila optimizacija sinteze paladijevega kompleksa z dvema Py-tzNHC ligandoma. Sintezo smo pričeli s pripravo izhodnega azida, ki mu je sledila 'klik' reakcija s terminalnim acetilenom do ustreznega triazola. V naslednji stopnji smo tvorili ustrezen N-oksid. In sic...
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| Format: | Master Thesis |
| Language: | Slovenian |
| Published: |
2021
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| Online Access: | https://repozitorij.uni-lj.si/IzpisGradiva.php?id=125409 https://repozitorij.uni-lj.si/Dokument.php?id=141118&dn= https://plus.si.cobiss.net/opac7/bib/55217155?lang=sl |
| Summary: | Namen magistrskega dela je bila optimizacija sinteze paladijevega kompleksa z dvema Py-tzNHC ligandoma. Sintezo smo pričeli s pripravo izhodnega azida, ki mu je sledila 'klik' reakcija s terminalnim acetilenom do ustreznega triazola. V naslednji stopnji smo tvorili ustrezen N-oksid. In sicer z oksidacijo piridinskega dušika v dvofaznem sistemu kloroform-vodna raztopina. Kombinacija vodikovega peroksida in ocetne kisline se v prisotnosti žveplove(VI) kisline in situ pretvori v peroksiocetno kislino, ki služi kot oksidant pri sami reakciji. Sledilo je metiliranje triazolnega obroča na poziciji N3. Poleg dušika na triazolnem obroču se je metiliral tudi kisik na piridinskem dušiku, zato smo v naslednjem koraku z redukcijo s cinkom v prisotnosti NH4BF4 cepili vez N–O in kot produkt dobili s piridinom funkcionaliziran triazolijev tetrafluoroborat, ki služi kot ligand pri pripravi paladijevega kompleksa. Kot vir paladija za tvorbo želenega kompleksa smo uporabili PdCl2, kot bazo pa Cs2CO3. Pri tem se je en ligand vezal bidentatno, drugi pa le monodentatno. Da smo zagotovili bidentatno vezavo tudi drugega liganda, smo morali izvesti odstranitev kloridnega iona iz kovinskega centra z uporabo AgBF4. Tako smo uspešno sintetizirali mezoionski paladijev(II) kompleks, ki je uporaben v številnih reakcijah spajanja. The main goal of master's thesis was the optimization of the synthesis of a planar palladium complex, bearing two Py-tzNHC ligands. In the first step the starting azide was formed, which reacted in a ‘click’ reaction with desired alkyne into the appropriated triazole. In the next step pyridine nitrogen was oxidized into N-oxide using biphasic system chloroform-water. Peroxyacetic acid was used as an oxidant, which was formed in situ between hydrogen peroxide and acetic acid in the presence of catalytic amounts of sulphuric(VI) acid. Oxidation was followed by methylation of the triazole ring at position N3. In addition to the nitrogen at the triazole ring, pyridine N-oxide atom was also methylated. N–O bond cleavage in the subsequent step was achieved by using activated zinc in the presence of NH4BF4 to afford a pyridine-functionalized triazolium tetrafluoroborate, which served as a ligand in the preparation of the desired mesoionic palladium complex. For the preparation of targeted complex, PdCl2 was chosen as the palladium source in the presence of Cs2CO3 as a base. One ligand coordinated in a bidentate, and the other in monodentate fashion. To achieve bidentate coordination of both ligands, the abstraction of chloride ion from the metal centre had to be performed, which was achieved by using AgBF4. With that the desired mesoionic palladium(II) complex, broadly used as a versatile catalyst for various cross-coupling reactions, was successfully synthesized under optimized reaction conditions. |
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