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Investigations into late transition metal pincer complexes as possible direct partial oxidation catalysts

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Please use this identifier to cite or link to this item: http://hdl.handle.net/1928/12089

Investigations into late transition metal pincer complexes as possible direct partial oxidation catalysts

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Title: Investigations into late transition metal pincer complexes as possible direct partial oxidation catalysts
Author: Lansing, Raymond B. Jr
Advisor(s): Kemp, Richard A.
Committee Member(s): Paine, Robert T.
Wang, Wei
Curro, John
Department: University of New Mexico. Dept. of Chemistry
Subject(s): Pincer
LC Subject(s): Transition metal complexes.
Oxidizing agents.
Degree Level: Doctoral
Abstract: This investigation examined aspects of a potential catalytic route for the partial oxidation of organic substrates using molecular oxygen as the oxidant. The proposed cycle begins with the insertion of molecular oxygen into a metal hydride bond to generate a metal hydroperoxide. The next step involves the transfer of an oxygen atom to an acceptor substrate to generate an oxidized species and a metal hydroxide. The starting metal hydride can then be regenerated in two viable ways, either through use of CO or H2. The experimental plan involved the syntheses and characterization of new inorganic and organometallic complexes, and it focused on PCP and related pincer ligand systems bound to Group 9 and 10 transition metal hydrides as the potential catalyst. A prominent feature of these pincer complexes is the opportunity for modification of their electronic and steric properties. The first part of the research involved the generation of pincer metal hydrides based on a neutral ligand (PNP) as compared to its anionic counterpart (PCP). Several new PNP-Rh-H complexes were prepared and their reactions with molecular oxygen were investigated. Unfortunately, the isolation of a rhodium hydroperoxide was not achieved. The investigation reveals that these Rh(I) species are unstable and decompose immediately when allowed to react with molecular oxygen. Another PNP system was investigated in order to expand options for the potential catalytic cycle. In this case, an Ozerov-type anionic PNP ligand was used to synthesize Group 10 pincer metal hydrides. Several new symmetric PNP-M-H (M = Ni, Pd, Pt) complexes were prepared and characterized. Modification of these PNP ligands was accomplished, resulting in new unsymmetric and racemic chiral ligands and metal complexes. Several of these PNP-Pd-H complexes have been shown to react with molecular oxygen to generate palladium hydroperoxides. The oxygen atom transfer ability of these complexes was investigated through reaction with several organic substrates. As yet, however, no evidence has been observed to indicate partial oxidation via oxygen atom transfer.
Graduation Date: December 2010
URI: http://hdl.handle.net/1928/12089

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