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Title Selective aerobic oxidations catalyzed by manganese(III) complexes using redox-active ligands
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Date Accessioned
Degree PhD
Discipline/Department Chemistry and Biochemistry
Degree Level doctoral
University/Publisher Georgia Tech
Abstract Selective oxidations are important for the functionalization of compounds in organic synthesis and chemical industry. Using O2 as a terminal e- acceptor would be ideal because it is cheap and environmentally friendly, but aerobic oxidations are often prone to unselective free radical autoxidation. Recently developed palladium catalysts use O2 as a selective multi-electron oxidant for various organic transformations. Although these methods are powerful and sophisticated, the lower cost of base metals makes them attractive as potential alternatives. The challenge is to develop methods for effecting multi-electron transformations at metals that typically prefer one electron changes. To this end, the development of manganese(III) complexes containing redox-active ligands as catalysts for selective oxidase-type oxidation of organic substrates was pursued. Bis(tetrabromocatecholato) manganese(III) complexes were shown to aerobically oxidize catechols to form quinones and H2O2. This reactivity was extended to other alcohol and amine substrates. In these reactions, the non-innocent tetrabromocatecholate ligands may impart a multi-electron character to the metal. To directly probe the intermediacy of ligand-centered radicals in catalytic turnover, a series of structurally similar manganese(III) complexes with aminophenol-derived ligands were prepared and characterized. The capacity of these ligands to undergo low-energy redox changes, allowed for isolation of an electron transfer series spanning two redox states without a change in oxidation state at the metal center. The ligand-centered redox events were a key feature in aerobic homocoupling of Grignard reagents.
Subjects/Keywords Oxidation chemistry; Metal catalysts; Metalloenzymes; Manganese; Manganese catalysts; Oxidases; Oxidation
Contributors Jake Soper (Committee Chair); Angus Wilkinson (Committee Member); Christoph Fahrni (Committee Member); Christopher Jones (Committee Member); Kent Barefield (Committee Member)
Country of Publication us
Record ID handle:1853/42827
Repository gatech
Date Indexed 2020-05-13
Issued Date 2011-11-08 00:00:00
Note [degree] PhD; [advisor] Committee Chair: Jake Soper; Committee Member: Angus Wilkinson; Committee Member: Christoph Fahrni; Committee Member: Christopher Jones; Committee Member: Kent Barefield;

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