Atom transfer reactions of high-valent rhenium and molybdenum oxo catalysts: Applications in oxygen atom transfer, hydrosilylation, and deoxydehydration of diols
Abstract
The objective of my research is to investigate the reaction chemistry of rhenium and molybdenum compounds with emphasis on their role in molecular catalysis. I determine reaction mechanisms by studying chemical kinetics, characterizing intermediates, and developing structure-function correlations. The LReO3 trioxo core is the primary framework used for catalytic reductions. In contrast, less research has involved the use of the dioxo rhenium [L2ReO2+] framework. My research has involved the full characterization of new oxorhenium cationic complexes and their successful use for hydrosilylation reactions. I also synthesized several complexes involving a oxo-imido framework [L2Re(O)(NR)+ ]. An attractive feature of the oxo-imido compounds is their tunability (electronic and steric) by changing the R-group on the nitrogen. In contrast to Re catalysts, my research has also involved a novel and simple synthesis to molybdenum salalen complexes and their application in catalytic hydrosilylation. Solvent effects, radical scavenger probes, and other mechanistic considerations reveal that the monooxo molybdenum(IV) is the most likely active form of the catalyst. Catalytic epoxidation and dihydroxylation of alkenes is a well studied reaction and widely used in organic synthesis and industry. Its prominence is due in part to our reliance on petroleum-based chemicals for the preparation of high value-added organics (HVO) that contain heteroatom functionality. In contrast, the reverse reaction, deoxygenation of epoxides and diols to make olefins, is less developed. My research has involved an efficient catalytic method for the deoxygenation of epoxides and diols using methyltrioxo rhenium (MTO) as a catalyst, molecular hydrogen (H2) as the reductant, under mild conditions, 150°C and 80-300 psi. This reaction is appealing in the context of making value-added organics from biomass.
Degree
Ph.D.
Advisors
Abu-Omar, Purdue University.
Subject Area
Inorganic chemistry
Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server.