Bulk Gold-Catalyzed Oxidations of Amines and Benzyl Alcohol Using Amine N-Oxides as Oxidants

Klobukowski, Erik R.; Angelici, Robert J.; Woo, L. Keith

doi:10.1007/s10562-011-0758-0

Cited by 16 publications

(14 citation statements)

References 33 publications

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“…A noble metal that has attracted particular interest is gold. Bulk Au is inert and is the only transition metal that is not catalytically active, except in very isolated cases (11,12). The inability of bulk Au surfaces to activate O 2 is the main factor limiting their activity as an oxidation catalyst.…”

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confidence: 99%

Oxidation of nanoscale Au–In alloy particles as a possible route toward stable Au-based catalysts

Sutter

Tong

Jungjohann

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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The oxidation of bimetallic alloy nanoparticles comprising a noble and a nonnoble metal is expected to cause the formation of a single-component surface oxide of the nonnoble metal, surrounding a core enriched with the noble metal. Studying the room temperature oxidation of Au-In nanoparticles, we show that this simple picture does not apply to an important class of bimetallic alloys, in which the oxidation proceeds via predominant oxygen diffusion. Instead of a crystalline In 2 O 3 shell, such oxidation leads to an amorphous shell of mixed Au-In oxide that remains stable to high temperatures and whose surface layer is enriched with Au. The Au-rich mixed oxide is capable of adsorbing both CO and O 2 and converting them to CO 2 , which desorbs near room temperature. The oxidation of Au-In alloys to a mixed Au-In oxide shows significant promise as a viable approach toward Au-based oxidation catalysts, which do not require any complex synthesis processes and resist deactivation up to at least 300°C.transmission electron microscopy | temperature programmed desorption | X-ray photoelectron spectroscopy T he importance of metal nanoparticles for a wide variety of applications, e.g., in catalysis, sensing, etc., has sparked interest in understanding and controlling their oxidation. The formation of an oxide layer negatively affects performance in applications that require pure metal surfaces. However, oxidation can be advantageous as it opens a way for engineering complex structures. Our understanding of room temperature oxidation has been established primarily in studies on the oxidation of bulk materials or planar films (1). Most of this insight should apply directly to the oxidation of nanoparticles, but important aspects arise in the geometry of small particles. For example, the high curvature in a nanoparticle can drive oxidation to larger thicknesses than in the planar case (2-4). Nanoscale junctions and interfaces to other materials can promote enhanced oxidation, as well as the formation of well-ordered epitaxial oxide segments (5). The oxidation of nanoparticles is also a powerful mechanism to produce nanoscale heterostructures. Metals that oxidize via predominant anion diffusion [In (2, 5), Pb (6), Sn, among others] form metal-oxide core-shell nanoparticles. For metals that oxidize via fast cation diffusion [Co (7), Al (6), Fe (8), Ni (9), among others], nanoscale porosity buildup creates hollow oxide nanocrystals that can be used as cages, e.g., to be filled with different materials (7) for storage or protection.Bimetallic (alloy, core-shell, etc.) nanoparticles promise widely tunable properties, and much progress has recently been made in their controlled synthesis (10). The oxidation of bimetallic nanoparticles has been studied much less than that of elemental metals, but it could provide even more interesting opportunities for the fabrication of functional nanomaterials, for example in catalysis.Alloys that comprise a noble and a less noble metal component are of interest because their oxidation can give ...

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mentioning

confidence: 99%

Oxidation of nanoscale Au–In alloy particles as a possible route toward stable Au-based catalysts

Sutter

Tong

Jungjohann

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…Substrate conversions varied between 87 % and 98 % after 10 h of reaction time. In the year 2012, Woo and co‐workers were the first to report a gold catalyzed oxidative dehydrogenation of dibenzylamine using TMAO as the oxidant . By reacting 1 mmol of pure gold powder and 0.066 mmol of TMAO with 0.012 mmol of Bn 2 NH they could reach 77 % of the imine product within 24 h in CD 3 CN at 60 °C.…”

Section: Resultsmentioning

confidence: 99%

Two Simple and Highly Efficient Variants of the Griffith‐Ley Oxidation of Alcohols

et al. 2020

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The Griffith‐Ley oxidation of alcohols to aldehydes and ketones is performed with either RuCl3 ⋅ (H2O)x or a highly stable, well‐defined ruthenium catalyst and with cheap trimethylamine N‐oxide (TMAO) as the oxygen source. The use of n‐heptane as the solvent, which forms a second phase with TMAO and a part of the alcohol, allows the reactions to be performed with a minimum amount of catalyst. This results in high local concentrations and thus to very rapid conversions. Detailed quantum chemical calculations suggest, that the Griffith‐Ley oxidation not necessarily requires high oxidation states of ruthenium but can also proceed with RuII/RuIV species.

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“…Bulk Au is the only transition metal that is not reactive, except in isolated cases. 24 The inability of bulk Au surfaces to activate O 2 is the main cause for their low activity in oxidation reactions. If, however, a supply of atomic oxygen is established, Au can become exceptionally active.…”

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confidence: 99%

Alloy oxidation as a route to chemically active nanocomposites of gold atoms in a reducible oxide matrix

et al. 2016

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Bulk Gold-Catalyzed Oxidations of Amines and Benzyl Alcohol Using Amine N-Oxides as Oxidants

Cited by 16 publications

References 33 publications

Oxidation of nanoscale Au–In alloy particles as a possible route toward stable Au-based catalysts

Oxidation of nanoscale Au–In alloy particles as a possible route toward stable Au-based catalysts

Two Simple and Highly Efficient Variants of the Griffith‐Ley Oxidation of Alcohols

Alloy oxidation as a route to chemically active nanocomposites of gold atoms in a reducible oxide matrix

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