The Development of Phosphine-Free Manganese Complexes and Their Applications in Catalytic Hydrogen Transfer and Hydroelementation Reactions

Das, Kuhali (2022) The Development of Phosphine-Free Manganese Complexes and Their Applications in Catalytic Hydrogen Transfer and Hydroelementation Reactions. PhD thesis, Indian Institute of Science Education and Research Kolkata.

Text (PhD thesis of Kuhali Das (17RS042)) 17RS042.pdf - Submitted Version Restricted to Repository staff only Download (28MB)

Abstract

The vast and progressive area of synthetic chemistry has prevailed to improvise the new routes to complex structural frameworks, which are found in the core of different pharmaceuticals, agrochemicals, materials, and other basic amenities of living beings. Continual efforts have always been imparted on making the processes more environmentally friendly, atom-economical, and cost-effective. From merely accelerating a reaction, the area of catalysis has come a long way in developing reaction methodologies and performing critical organic transformations those otherwise would have been tough to achieve. The reductive transformations of organic molecules imparted significant contribution to achieving this molecular complexity by employing Earth’s renewable resources. In this context, the hydrogen transfer reactions, which involve the shuffle of a molecule of hydrogen from one molecule to another, are recognized as one of the most atom economical and greener pathways. Apart from achieving simple hydrogenation, the downstream cascade reactions like borrowing hydrogenation (BH), acceptorless dehydrogenative coupling (ADC) reactions are recognized as viable synthetic tools for C-C and C-X (X = N, O) bond formation. The significant advantages include the employment of readily available and cheaper resources as starting materials and the formation of green by-products water and hydrogen. Another important methodology is the hydroboration and hydrosilylation reactions which, alongside performing the overall reductions, also provide way to several critical synthons for different organic transformations. The high reactivity of noble metals tempted chemists to employ them as catalysts in these reactions. However, the toxicity and higher cost resulting from the scarcity of these metals limited their applicability in the long term. The 3d-metals, on the other hand, are much cheaper and less toxic compared to 4d-and 5d-metals. In this regard, manganese is the third most abundant transition metal on Earth’s crust and much cheaper and less toxic. These features make this a viable candidate for “Sustainable Synthesis”. This thesis will aim at the development of manganese complexes based on the air-stable, cheap, and phosphine-free ligand backbone. The catalytic activity of these manganese complexes towards C-X bond formation will also be discussed in detail.

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