Rhenium Mediated Formation of N-Containing Organic Compounds by Nitride Transfer
von Sesha Kisan
Datum der mündl. Prüfung:2022-08-08
Betreuer:Prof. Dr. Sven Schneider
Gutachter:Prof. Dr. Sven Schneider
Gutachter:Prof. Dr. Franc Meyer
EnglischN-containing organic compounds occur in all the organisms, such as in the form of amino acids (and thus proteins), nucleic acids (DNA and RNA), and in the form of energy transfer molecule adenosine triphosphate. The human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. Therefore, N-containing organic compounds are a very crucial group of compounds that help to sustain life on earth. Ammonia is one of the most important raw materials in the synthesis of nitrogen-containing compounds such as amine, nitrile, and N-heterocyclic organic compounds. Initially, ammonia was obtained from N2 by biological enzymatic nitrogen fixation to ammonia with the help of bacteria, however, the process is not atom economical. Similarly, in the early 20th century, Fritz Haber developed a new process for ammonia production, which increased the production, of ammonia significantly. However, they used very harsh conditions. Alternative to these, ammonia and other nitrogen compounds can be synthesized directly from terminal metal nitrides by the N-transfer homogeneous pathway. Till date, many terminal transitions metal nitrides have been reported in the literature. These nitrides can be synthesized from different nitrogen sources such as from dinitrogen gas, via ammonia deprotonation or the decaying of azide, hydrazine, and its derivatives. Here, the synthesis of rhenium nitride and synthesis of nitrogen-containing organic compounds is demonstrated with a [ReBr3 (PNP)] platform. The starting complex is treated with TMS-N3 or N2 to get the rhenium terminal nitride which is further employed in the metal-ligand cooperative reaction to getting the benzamide and benzonitrile and further the compounds are synthesized selectively by using the PCET method. Moreover, the key intermediate is synthesized and characterized. A kinetic study is conducted to investigate the mechanistic pathway of metal-ligand cooperative reactions, but unfortunately, the mechanistic pathway could not depict it as it provided a rate of zero order. Hammett plot for the synthesis of substituted benzoyl imido complexes is plotted which indicates the electron-withdrawing group substituted benzoyl bromide gives better reactivity due to increasing the electrophilicity of the carbonyl carbon, which makes a nucleophilic attack of nitride easier. A substrate scope for the synthesis of substituted benzonitrile is created where the formation of para-substituted benzonitrile is demonstrated using terminal rhenium nitride complex and substituted benzoyl bromide in presence of reductant and acids.
Keywords: Rhenium, Nitride Transfer, Nitrides, Nitrogen, Benzamide, Benzonitrile, Metal-ligand cooperativity, PCET method, Kinetics, Hammett plot