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作者 Shalyaev, Kirill V
書名 Catalysis of hydrocarbon oxidation by polyhalogenated ruthenium porphyrins and studies on the origins of enantioselectivity in metalloporphyrin catalyzed olefin epoxidations
國際標準書號 9780599196162
book jacket
說明 201 p
附註 Source: Dissertation Abstracts International, Volume: 60-02, Section: B, page: 0643
Thesis (Ph.D.)--Princeton University, 1998
Polyhalogenated ruthenium porphyrin complexes such as RuII(TPFPP)(CO) were found to be efficient catalysts for the oxygenation of hydrocarbons including secondary alkanes and benzene in the presence of 2,6-dichloropyridine N-oxide as oxidant under mild non-acidic conditions. Up to 15,000 turnovers and rates of 800 TO/min were obtained in hydroxylation of adamantane. The hydroxylation of cis-decalin gave cis-9-decalol and cis-decalin-9,10-diol, exclusively. Benzene was oxidized to benzoquinone
Based on the kinetic and spectroscopic evidence RuVI(TPFPP)(O) 2, RuIV(TPFPP)(O), RuII(TPFPP)(CO) and RuIV(TPFPP)Cl2 observed during catalysis have been ruled out as candidates for the active intermediates responsible for the high efficiencies and turnover rates. A mechanism is proposed which incorporates a "slow" oxidation cycle, mediated by oxoRu(IV) and trans-dioxoRu(VI) porphyrin complexes, and a "fast" cycle where metastable Ru(III) and oxoRu(V) intermediates play an important role. The fastest rates of adamantane hydroxylation and cyclohexene epoxidation were achieved with RuIV(TPFPP)Cl2 catalyst in the presence of zinc amalgam. This reductive activation is consistent with the formation of an active Ru(III) intermediate in situ by a one-electron reduction of the Ru(IV) porphyrin. The synthesis and EPR characterization of authentic Ru(III) alkoxy porphyrin complexes is described
Polyhalogenated ruthenium porphyrin complexes, RuII(TPFPP)(CO) and RuII(TPFPPBr8)(CO), were covalently bound to 3-aminopropylsilica. The new heterogeneous catalysts were found to be efficient, robust and selective in oxygenation of a variety of hydrocarbons with 2,6-dichloropyridine N-oxide. Over 6,000 catalytic turnovers was obtained in hydroxylation of cyclohexane. Epoxidation of cis-stilbene stereospecifically afforded cis-epoxide in up to 84% yield. Cis-decalin was oxidized to cis-9-decalinol in 90% yield. No significant leaching of ruthenium porphyrin from the solid support was found under the conditions of oxidative catalysis
The origins of chiral induction by asymmetric porphyrin and salen complexes were investigated by FT-NMR T1 relaxation techniques. The transition state for olefin epoxidation with high-valent metal-oxo species was modeled by coordinating epoxides to paramagnetic copper complexes of the corresponding ligands. The epoxide enantiomer that better fit the chiral cavity of the catalyst, as revealed by T1 relaxation measurements, was also the major product of catalytic olefin epoxidation. These results are consistent with the 'lock-and-key' mechanism of asymmetric catalysis by metalloporphyrins
School code: 0181
DDC
Host Item Dissertation Abstracts International 60-02B
主題 Chemistry, Inorganic
Chemistry, Organic
0488
0490
Alt Author Princeton University
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