Metalloenzyme‐Inspired Catalysis: Selective Oxidation of Primary Alcohols with an Iridium–Aminyl‐Radical Complex

Königsmann, Martin; Donati, Nicola; Stein, Daniel; Schönberg, Hartmut; Harmer, Jeffrey; Sreekanth, Anandaram; Grützmacher, Hansjörg

doi:10.1002/anie.200605170

Cited by 108 publications

(46 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To drive a dehydrogenation reaction toward separate generation of protons and electrons requires a stoichiometric oxidant combined with a weak base as a proton sink, and for the reverse reaction (catalytic hydrogenation), a stoichiometric amount of reductant is necessary combined with a (weak) conjugate acid as a proton source. Herein, we studied two iridium(I) complexes, [Ir(trop 2 DACH)][OTf] (5), a highly efficient catalyst used in the dehydrogenation of a broad range of primary alcohols to aldehydes (44), and the related [Ir(trop 2 DAD)][OTf] (6) (45), which features an unsaturated and sterically less encumbered ligand framework, as reversible alcohol dehydrogenation-hydrogenation catalysts (Scheme 2).…”

Section: Reversible Oxidative Dehydrogenation Of Primary Alcohols Witmentioning

confidence: 99%

“…Dehydrogenation of benzylic and allylic alcohols proceeds at room temperature with very low loadings of 5 (0.01 mol%) and requires catalytic amounts of strong base (e.g., KO t Bu; 0.03 mol%) and stoichiometric 1,4-benzoquinone (BQ) as a hydrogen (H 2 ) scavenger (44,46). We now report our findings with 5 and 6 for alcohol dehydrogenation in terms of separately extracting protons and electrons through chemical catalysis results that used stoichiometric oxidants (e.g., ferrocenium) combined with a weak base (phenolate).…”

Section: Reversible Oxidative Dehydrogenation Of Primary Alcohols Witmentioning

confidence: 99%

See 1 more Smart Citation

Reversible catalytic dehydrogenation of alcohols for energy storage

Bonitatibus

Chakraborty

Doherty

et al. 2015

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

124

View full text Add to dashboard Cite

Reversibility of a dehydrogenation/hydrogenation catalytic reaction has been an elusive target for homogeneous catalysis. In this report, reversible acceptorless dehydrogenation of secondary alcohols and diols on iron pincer complexes and reversible oxidative dehydrogenation of primary alcohols/reduction of aldehydes with separate transfer of protons and electrons on iridium complexes are shown. This reactivity suggests a strategy for the development of reversible fuel cell electrocatalysts for partial oxidation (dehydrogenation) of hydroxyl-containing fuels.

show abstract

Section: Reversible Oxidative Dehydrogenation Of Primary Alcohols Witmentioning

confidence: 99%

Section: Reversible Oxidative Dehydrogenation Of Primary Alcohols Witmentioning

confidence: 99%

Reversible catalytic dehydrogenation of alcohols for energy storage

Bonitatibus

Chakraborty

Doherty

et al. 2015

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

124

View full text Add to dashboard Cite

show abstract

“…It is proposed to be a key intermediate in the catalytic oxidation of alcohols to aldehyde, with potassium tert-butoxide as a base [52]. Complex C can be generated from the corresponding amine by deprotonation with KOtBu and subsequent oxidation with para-benzoquinone.…”

Section: Nitrogen-centered Radicals In Catalysismentioning

confidence: 99%

EPR Spectroscopy as a Tool in Homogeneous Catalysis Research

et al. 2015

View full text Add to dashboard Cite

In the context of homogeneous catalysis, openshell systems are often quite challenging to characterize. Nuclear magnetic resonance (NMR) spectroscopy is the most frequently applied tool to characterize organometallic compounds, but NMR spectra are usually broad, difficult to interpret and often futile for the study of paramagnetic compounds. As such, electron paramagnetic resonance (EPR) has proven itself as a useful spectroscopic technique to characterize paramagnetic complexes and reactive intermediates. EPR spectroscopy is a particularly useful tool to investigate their electronic structures, which is fundamental to understand their reactivity. This paper describes some selected examples of studies where EPR spectroscopy has been useful for the characterization of open-shell organometallic complexes. The paper concentrates in particular on systems where EPR spectroscopy has proven useful to understand catalytic reaction mechanisms involving paramagnetic organometallic catalysts. The expediency of EPR spectroscopy in the study of organometallic chemistry and homogenous catalysis is contextualized in the introductory Sect. 1. Section 2 of the review focusses on examples of C-C and C-N bond formation reactions, with an emphasis on catalytic reactions where ligand/substrate non-innocence plays an important role. Both carbon and nitrogen centered radicals have been shown to play an important role in these reactions. A few selected examples of catalytic alcohol oxidation proceeding via related N-centered ligand radicals are included in this section as well. Section 3 covers examples of the use of EPR spectroscopy to study important commercial ethylene oligomerization and polymerization processes. In Sect. 4 the use of EPR spectroscopy to understand the mechanisms of Atom Transfer Radical Polymerization is discussed. While this review focusses predominantly on the application of EPR spectroscopy in mechanistic studies of C-C and C-N bond formation reactions mediated by organometallic catalysts, a few selected examples describing the application of EPR spectroscopy in other catalytic reactions such as water splitting, photo-catalysis, photo-redox-catalysis and related reactions in which metal initiated (free) radical formation plays a role are included as well. EPR spectroscopic investigation in this area of research are dominated by EPR spectroscopic studies in isotropic solution, including spin trapping experiments. These reactions are highlighted in Sect. 5. EPR spectroscopic studies have proven useful to discern the correct oxidation states of the active catalysts and also to determine the effective concentrations of the active species. EPR is definitely a spectroscopic technique that is indispensable in understanding the reactivity of paramagnetic complexes and in conjunction with other advanced techniques such as X-ray absorption spectroscopy and pulsed laser polymerization it will continue to be a very practical tool.

show abstract

“…[1, 2] The cooperative effect of redox-active ligands and metal sites in enzymatic systems, [3] and more recently in synthetic systems, [4] adds significant flexibility to catalyst function. Depending on the relative energies of the redoxactive orbitals, metal complexes with proradical ligands can exist in a limiting description as a metal-ligand radical (M n+ (L • )) or a high valent metal complex (M (n+1)+ (L - )).…”

mentioning

confidence: 99%