Hydroxyl Functionalised Perimidine-3-ium Salts

Yadav, Prashant and Prabusankar, G (2019) Hydroxyl Functionalised Perimidine-3-ium Salts. Masters thesis, Indian institute of technology Hyderabad.

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Abstract

During the recent times N-Heterocyclic carbenes (NHCs) have gained importance and now they constitute a new group of ligands that have become a part of the organometallic chemistry and metal catalysts. Presently, the recent research is focused on two aspects; firstly, discovering the uses of NHCs based ligands for catalyst, and secondly on the developing a novel NHC ligands. In view of these developments, we were interested in developing and synthesizing the new “expanded ring” carbenes, i.e. NHCs possessing more than 5 atoms in their heterocyclic ring systems unlike the NHCs that are a part of a 5-membered imidazolium-based moiety. The NHCs having either 6 or 7 atoms in heterocyclic ring still remain dormant and unexplored comparatively and their properties and reactivity is also not known, primarily because of the difficulties faced previously in synthesising the expanded ring carbene compounds. The free carbenes have been synthesized several times during the recent times and they have been found to be astonishingly stable. The NHCs having more than five atoms in the ring tend to show basic properties and they possess unique structural properties too. For example, consider, the angle formed by the two nitrogen atoms at the carbon atom present at the centre of larger ring NHCs are comparatively larger when compared with the usual five membered NHC’s, as a result of this large angle the substituents attached to the nitrogen atom are forced to come closer to the metal centre. Donor-functionalised NHCs have also found a significant part in metal complexes for catalysis and also in areas related to the organometallic chemistry. The aim of this thesis is to develop the novel 6-membered NHC based on perimidine. The perimidine based NHC that we developed is bi-dentate and it can use the oxygen atom which is in the close vicinity of the carbene, and can bind with the metal atom, thereby increasing the denticity of the ligand. The NHC’s counter ion was changed by simple ion exchange reaction for varied solubility in different solvents.

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