Shada, Arun Dixith Reddy. Unconventional approaches to C-H bond activation and alkane functionalization by PCP pincer iridium complexes. Retrieved from https://doi.org/doi:10.7282/t3-4dwr-ax54
DescriptionThis thesis is organized into three themes: (1) C-H bond activation and functionalization studies by PCP type pincer ligated iridium acetate hydride complexes, (2) Investigating the reactivity of four-coordinate (pincer)Ir(CO) complexes toward alkane hydrocarbonylation reactions, and (3) Protons coupled electrons transfer driven alkane dehydrogenation using iridium-pincer complexes.
In the first part of this thesis, we describe the preparation of a novel class of PCP-type pincer iridium complexes with acetate ligands. We examined the catalytic activity of (pincer)Ir(OAc)(H) towards transfer and acceptorless dehydrogenation of alkanes. We have studied Lewis Acid’s role in the reactivity of (pincer)Ir(OAc)(H) towards alkene by studying the alkene insertion into iridium hydride bond. We have shown intramolecular C-H bond activations with (pincer)Ir(OAc)(H) in the presence of oxidants. Finally, comparisons were drawn between PCP and Phebox systems towards alkane C-H bond activations.
In the second part of this thesis, we explored the unprecedented carbonylation of alkanes in the presence of four-coordinate (pincer)Ir(CO) complexes. Employing a unique acid-catalyzed route, we showed stoichiometric hydrocarbonylation starting from (tBu4PCP)Ir(Et)(CO)(H) to give n-propanol. Although we did not observe catalytic activity towards alkane hydrocarbonylation, we proposed an alkane carbonylation mechanism and have carried out mechanistic studies. We then demonstrated the first examples of hydroformylation of ethylene using (pincer)Ir(CO) complexes under mild conditions. These reactions were shown to be co-catalyzed in the presence of Lewis Acids.
In the last part of this thesis, we described the first example of alkane dehydrogenation by proton-coupled electron transfer using (pincer)Ir complexes and a pair of oxidants and bases. Employing silver salts as oxidants and t-butoxide as a base, we have shown dehydrogenation of cyclooctane with (tBu4PCP)Ir(H)2 complex. Up to 97% yield was achieved with respect to oxidant and base, and up to 15 catalytic turnovers with respect to iridium, using t-butoxide as base coupled with various oxidants. Mechanistic studies revealed that oxidants and bases generate the active Ir(I), which dehydrogenate alkanes.