Catalytic Conversions in Water. Part 22: Electronic Effects in the (Diimine)palladium(II)‐Catalysed Aerobic Oxidation of Alcohols

Brink, Gerd‐Jan ten; Arends, Isabel W. C. E.; Hoogenraad, Marcel; Verspui, Göran; Sheldon, Roger A.

doi:10.1002/adsc.200390057

Cited by 107 publications

(58 citation statements)

References 53 publications

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“…Another specific point of the present Pd/SiO 2 -Al 2 O 3 catalyst is that all the substituted benzyl alcohols investigated here exhibit lower reactivities than benzyl alcohol. However, for many homogeneous Pd complex catalysts, [32,33] it has been reported that the reactivities of substituted benzyl alcohols with electron-donating substituents are higher than that of benzyl alcohol, while the presence of electron-withdrawing substituents decreases the reactivity. The same phenomenon has also been reported for some heterogeneous catalysts such as Ru(OH) x /Al 2 O 3 .…”

Section: Resultsmentioning

confidence: 99%

“…This is also a quite unique observation because the benzyl alcohols with an electron-donating substituent, which can facilitate the b-hydride elimination, show higher reactivities in many homogeneous systems. [32,33] We speculate that the lower reactivity of the substrates with electron-donating substituents in our case may stem from the lower ability of chemisorption of these substrates on the Pd sites because of the steric hindrance. This further supports the speculation that both the coordinately unsaturated sites and the terrace sites are required for obtaining a high intrinsic TOF for benzyl alcohol conversion.…”

Section: Structure-sensitivity Of Pd Nanoparticles-catalyzed Oxidatiomentioning

confidence: 93%

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Size‐Dependent Catalytic Activity of Supported Palladium Nanoparticles for Aerobic Oxidation of Alcohols

et al. 2008

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Silica-alumina (SiO 2 -Al 2 O 3 )-supported palladium catalysts prepared by adsorption of the tetrachloropalladate anion (PdCl 4 2À ) followed by calcination and reduction with either hexanol or hydrogen were studied for the aerobic oxidation of alcohols. The mean size of the Pd particles over the SiO 2 -Al 2 O 3 support was found to depend on the Si/Al ratio, and a decrease in the Si/Al ratio resulted in a decrease in the mean size of the Pd nanoparticles. By changing the Si/Al ratio, we obtained supported Pd nanoparticles with mean sizes ranging from 2.2 to 10 nm. The interaction between the Pd precursor and the support was proposed to play a key role in tuning the mean size of the Pd nanoparticles. The Pd/SiO 2 -Al 2 O 3 catalyst with an appropriate mean size of Pd particles could catalyze the aerobic oxidation of various alcohols to the corresponding carbonyl compounds, and this catalyst was particularly efficient for the solvent-free conversion of benzyl alcohol. The intrinsic turnover frequency per surface Pd atom depended significantly on the mean size of Pd particles and showed a maximum at a medium mean size (3.6-4.3 nm), revealing that the aerobic oxidation of benzyl alcohol catalyzed by the supported Pd nanoparticles was structure-sensitive.

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Section: Resultsmentioning

confidence: 99%

Section: Structure-sensitivity Of Pd Nanoparticles-catalyzed Oxidatiomentioning

confidence: 93%

Size‐Dependent Catalytic Activity of Supported Palladium Nanoparticles for Aerobic Oxidation of Alcohols

et al. 2008

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“…[19] From 3a, several routes led to differently substituted 4,4'-biypridines (4a-6a) [19][20][21] (see Figure 2). Starting from commercially available mono-oxidised, mono-nitrated 10a, 11a was produced similarly to 5a.…”

Section: Mediator Preparationmentioning

confidence: 99%

Synthesis, Characterization and Application of New Rhodium Complexes for Indirect Electrochemical Cofactor Regeneration

et al. 2008

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Electroenzymatic synthesis often suffers from electrochemical reaction steps which proceed slower than the coupled enzyme reaction. For indirect electrochemical cofactor regeneration, we here report two new mediators with superior properties compared to the established rhodium complex (2,2'-bipyridyl)(pentamethylcyclopentadienyl)rhodium [Cp*Rh(2,2'-bipyridine)]. After constructing a robotic system for fast and reliable cyclic voltammetry measurements, we screened twelve rhodium complexes with substituted 2,2'-bipyridine ligands for their reduction potentials and catalytic activity towards the reduction of NADP. Promising complexes were investigated in more detail by cyclic voltammetry and under batch electrolysis conditions. The new complexes Cp*Rh(5,5'-methyl-2,2'-bipyridine) and Cp*Rh(4,4'-methoxy-2,2'-bipyridine) reduced NADP to NADPH three times faster than the established mediator, resulting in volumetric productivities of up to 136 mmol L À1 d À1 and turnover frequencies of up to 113 h À1. This increased reaction rate of these new mediators makes indirect electrochemical approach significantly more competitive to other methods of cofactor regeneration.Abbreviations: ADH = alcohol dehydrogenase; Ag j AgCl = silver j silver chloride reference electrode; bpy = 2,2'-bipyridine; ci = current increase; Cp* = pentamethylcyclopentadienyl; CV = cyclic voltammetry; Ep = peak potential; equiv = equivalent; NADP/ NADPH = nicotinamide adenine dinucleotide phosphate oxidised/reduced form.

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“…Many highly efficient catalysts for the aerobic oxidation of alcohols have been developed recently using palladium [8][9][10][11], platinum [12], ruthenium [13] and rhodium complexes [14][15][16][17]. In the interest of sustainability, there has been significant development in the use of more abundant and cheaper transition metals such as iron [18][19] and copper as active catalysts.…”

Section: Introductionmentioning

confidence: 99%

Room temperature aerobic oxidation of alcohols using CuBr2 with TEMPO and a tetradentate polymer based pyridyl-imine ligand

Kerton

2012

Applied Catalysis A: General

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Abstract.A series of tetradentate pyridyl-imine terminated Schiff-base ligands has been investigated for their ability in the catalytic oxidation of alcohols when combined with copper bromide (CuBr 2 ) and 2,2,6,6-tetramethylpiperidyl-1-oxy (TEMPO). Analogous bidentate ligands showed poorer catalytic activity and the ratio of Cu:ligand was of crucial importance in maintaining high yields. The polydimethylsiloxane (PDMS) derived pyridyl-imine terminated ligand combined with copper (II) ions affords an effective and selective catalyst for aerobic oxidations of primary and secondary alcohols under aqueous conditions. Preliminary mechanistic studies suggest that bimetallic complexes may be playing a role in the catalytic transformation. Graphical Abstract1

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Catalytic Conversions in Water. Part 22: Electronic Effects in the (Diimine)palladium(II)‐Catalysed Aerobic Oxidation of Alcohols

Cited by 107 publications

References 53 publications

Size‐Dependent Catalytic Activity of Supported Palladium Nanoparticles for Aerobic Oxidation of Alcohols

Size‐Dependent Catalytic Activity of Supported Palladium Nanoparticles for Aerobic Oxidation of Alcohols

Synthesis, Characterization and Application of New Rhodium Complexes for Indirect Electrochemical Cofactor Regeneration

Room temperature aerobic oxidation of alcohols using CuBr2 with TEMPO and a tetradentate polymer based pyridyl-imine ligand

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