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Catalysis, First-Row Metal, Mixed-Valence, Hydrodeoxygenation, Cluster, Hydrodesulfurization

Brown, Houston J. S.

Supervisor and department: Stryker, Jeffrey Chemistry

Examining committee member and department: Heinekey, D. Michael Chemistry, University of Washington Stryker, Jeffrey Chemistry Takats, Josef Chemistry West, Frederick Chemistry de Klerk, Arno Chemical and Materials Engineering

Department: Department of Chemistry

Specialization:

Date accepted: 2013-09-30T11:51:50Z

Graduation date: 2013-11

Degree: Doctor of Philosophy

Degree level: Doctoral

Abstract: Salt metathesis between CoCl2 and KNPEt3n provides a new route to the halide-substituted cobalt phosphoranimide cluster CoClNPEt34. This cluster is a useful precursor for the preparation of alkyl-capped cobalt phosphoranimide complexes. The methylated heterocubane CoMeNPEt34 was synthesized in high yield by transmetallation of CoClNPEt34 with Me2Mg•dioxane in dioxane. The structural, magnetic, and electrochemical properties of the cluster have been rigorously evaluated. The type III mixed-valence cluster CoMeNPEt34PF6 was prepared from CoMeNPEt34 by outer-sphere electron transfer with Cp2FePF6. The cationic cluster has been fully characterized. Both CoMeNPEt34 and CoMeNPEt34PF6 are active precatalysts for reductive C–S bond cleavage. The catalytic activity of CoMeNPEt34PF6 has been investigated in more detail. Under basic conditions, the mixed-valence cluster catalyzes the complete hydrodesulfurization of a number of organosulfur compounds under mild conditions 110–170°C, 1 atm H2: dibenzothiophene, 4,6-diethyldibenzothiophene, benzothiophene, 3-hexylthiophene, diphenyl sulfide, benzyl phenyl sulfide, and phenoxathiin. In all instances no products indicative of aromatic ring hydrogenation were noted. The desulfurization of dibenzothiophene was investigated over a range of temperatures. A preliminary mechanistic ‗road map‘ for the reaction was proposed. The mixed valence cluster CoMeNPEt34PF6 also catalyzes C–O bond hydrogenolysis of unstrained ethers. Aromatic, benzyl, and aliphatic C–O bonds are all cleaved under mild conditions. The substrate scope includes diphenyl ether, 4-methoxybiphenyl, 2,3-dihydrobenzofuran, 1,3-bis4-methoxyphenoxybenzene, dibenzofuran, and benzofuran. In no case were products indicative of aromatic ring hydrogenation noted. Catalytic hydrogenolysis in the presence of the Lewis acid AlMe3 results in higher turnover frequencies than those not including AlMe3. The presence of the Lewis acid also promoted further C–O bond reductions to give complete hydrodeoxygenation of resistant substrates.

Language: English

DOI: doi:10.7939-R33776137

Rights: Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.





Autor: Brown, Houston J. S.

Fuente: https://era.library.ualberta.ca/


Introducción



University of Alberta Mixed-Valence First-Row Metal Clusters for Catalytic Hydrodesulfurization and Hydrodeoxygenation by Houston John Stinson Brown A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy Department of Chemistry ©Houston John Stinson Brown Fall 2013 Edmonton, Alberta Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only.
Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the authors prior written permission. Abstract Salt metathesis between CoCl2 and [KNPEt3]n provides a new route to the halidesubstituted cobalt phosphoranimide cluster [CoCl(NPEt3)]4.
This cluster is a useful precursor for the preparation of alkyl-capped cobalt phosphoranimide complexes.
The methylated heterocubane [CoMe(NPEt3)]4 was synthesized in high yield by transmetallation of [CoCl(NPEt3)]4 with Me2Mg•dioxane in dioxane.
The structural, magnetic, and electrochemical properties of the cluster have been rigorously evaluated.
The type (III) mixed-valence cluster [CoMe(NPEt3)]4PF6 was prepared from [CoMe(NPEt3)]4 by outer-sphere electron transfer with Cp2FePF6.
The cationic cluster has been fully characterized.
Both [CoMe(NPEt3)]4 and [CoMe(NPEt3)]4PF6 are active precatalysts for reductive C– S bond cleavage.
The catalytic activity of [CoMe(NPEt3)]4PF6 has been investigated in more detail.
Under basic conditions, the mixed-valence cluster catal...





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