Struktura in reaktivnost paladijevih kompleksov z različnimi triazolilidenskimi ligandi

Podlogar, Tjaša (author), Gazvoda, Martin (mentor)

Cilj magistrskega dela je bila sinteza različnih s piridinom funkcionaliziranih triazolijevih soli in poskus priprave kompleksov med omenjenimi triazolijevimi solmi in kovinami prehoda, v katerih bi triazolijeve soli predstavljaje Py-tzNHC bidentatne karbenske ligande. Sinteze smo začeli s klik reakcijo med ustrezno izbranima acetilenom in azidom ter nato po literaturnih postopkih pripravili ustrezne trizolijeve soli. Pripravili smo 4 nove, v literaturi še neopisane, triazolijeve soli. Pripravili smo s piridinom funkcionalizirano triazolijevo sol, ki ima na triazolna dušika N 1 in N 3 vezani metilni skupini. Sintetizirana sol nam je služila kot prekurzor za ligand v paladijevemu kompleksu z dvem tovrstnima Py-tzNHC ligandoma, ki smo ga pripravili z deprotoniranjem omenjene soli s srebrovim(I) oksidom. Kompleks smo uporabili kot katalizator pri Sonogashirovem pripajanju brez bakra, žal se je izkazal slabše aktiven kot njegov analog, ki ima na N 1 vezano aromatsko, 4-Me-C 6 H 4 -, skupino. Omenjen paladijev kompleks z dvema Me skupina je tudi manj obstojen kot njegov analog, saj je po enem dnevu pri sobni temperaturi razpadel. Pripravili smo tudi s piridinom funkcionalizirano triazolijevo sol, ki ima 2-piridinski substituent vezan na triazolni obroč preko -CH mostička. Na mostovni ogljik je bila vezana še hidroksilna oziroma acetiloksi skupina. To triazolijevo sol smo poskusili uporabiti kot prekurzor za ligand pri pripravi ustrezenega paladijevega kompleksa, a ta triazolijeva sol že pod blagimi bazičnimi pogoji razpade na 3-metil-1-(p-tolil)-1H-1,2,3-triazol-3-ijev tetrafluoroborat. Razpad najverjetneje poteče po retro-aldolni reakciji, vendar nam tega ni uspelo nedvoumno potrditi niti z detekcijo 2-formilpiridina oziroma 2-pikolinske kisline niti z obratno, aldolno reakcijo 2-formilpiridina na 3-metil-1-(p-tolil)-1H-1,2,3-triazol-3-ijev tetrafluoroborat. Pri sintezi omenjene triazolijeve soli dobimo racemno zmes dveh enantiomerov, katera smo poskusili ločiti z resolucijo s pomočjo kristalizacije. Poleg opisanih triazolijevih soli smo pripravili tudi s piridinom funkcionalizirano kiralno triazolijevo sol. Sintezno smo začeli iz (R)-2-(1-azidoetil)piridina, v optično čisti obliki, ki je po klik reakciji z 1-etinil-4-metilbenzenom in nadaljni pretvorbi do ustrezne triazolijeve soli, vodil do prve takšne optično čiste spojine. Omenjena triazolijeva sol predstavlja prekurzor za kiralen karbenski Py-tzNHC ligand, ki bi po vezavi na kovino prehoda vodil do kiralnega organokovinskega kompleksa. Takšen kompleks bi lahko služil kot katalizator za stereoselektivne pretvorbe pri katalitskih reakcijah.

• Language: Slovenian
• Keywords: triazol, triazolijeva sol, kovine prehoda, paladij, kiralni organokovinski kompleks
• Work type: Master's thesis/paper
• Typology: 2.09 - Master's Thesis
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2019
• PID: 20.500.12556/RUL-113204
• COBISS.SI-ID: 1538506947
• Publication date in RUL: 12.12.2019

Secondary language

• Language: English
• Title: Structure and reactivity of palladium complexes with different triazolylidene ligands

Abstract

The goal of master thesis was the synthesis of different pyridine- functionalized triazolium salts and attempt to prepare their corresponding complexes with transition metals in which triazolium salts would represent Py-tzNHC bidentate carbene ligands. We started the synthesis with click reaction between appropriately selected acetylenes and azides and then we followed literature procedures to prepare corresponding triazolium salts. We synthesized 4 new triazolium salts. We prepared pyridine-functionalized triazolium salt with methyl group at the triazole nitrogens N 1  and N 3 . This salt was used as a ligand in palladium complex with two Py-tzNHC which was made by deprotonation with silver(I) oxide. Palladium complex was tested as a catalyst for copper-free Sonogashira reaction but it turned out to be less efficient than its analogue with aromatic, 4-Me-C 6 H 4 -, group bonded to nitrogen N 1 . Mentioned palladium complex with 2 methyl groups is also less stable than its arylated analogue as it decomposes at room temperature in one day. We also prepared pyridine functionalized triazolium salt which had 2-pyridine substituents bonded to triazolium ring over a –CHbridge, with additional OH or OAc group on the CH linker. We tried to use this triazolium salt as a precursor for ligand for the corresponding palladium complex but this triazolium salt decomposed already under mild basic conditions into 3methyl1(ptolyl)-1H-1,2,3-triazol-1-ium tetrafluoroborate. Decomposition probably occures through a retro-aldol reaction, however, we were unable to prove this neither with detection of 2-formylpyridine or 2-picolinic acid nor with reversed, aldol reaction of 2-fromylpyridine and 3-methy-1-(p-tolyl)-1H-1,2,3-triazol-3-ium tetrafluoroborate. The synthesis of the above mentioned triazolium salt furnished racemic mixture of 2 enantiomers which we tried to separate by resolution with help of crystalization. In addition, we also prepared optically pure pyridine-functionalized triazolium salt. We started the synthesis from optical pure (R)-2-(1-azidoethyl)pyridine which we reacted with 1-etynyl-4-methylbenzene and then further converted to the corresponding triazolium salt by methylation. This is the first prepared optical pure compound of this type. This triazolium salt represents a precursor for chiral carbene Py-tzNHC ligand which would after bonding to transition metal lead to chiral organometallic complex. This kind of complex could serve as a catalyst for stereoselective transformations.

• Keywords: triazole, triazolium salt, transition metals, palladium, chiral organometallic complex