Katalytische Oxidation von Wasser durch einen Iridiumkomplex mit einem starken Carben‐Donorliganden

Lalrempuia, Ralte; McDaniel, Neal D.; Müller‐Bunz, Helge; Bernhard, Stefan; Albrecht, Martin

doi:10.1002/ange.201005260

Cited by 82 publications

(20 citation statements)

References 70 publications

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“…[1,2] To construct a (photo)electrochemical H 2 /O 2 evolution system, oxygen evolving catalysts (OECs) need to be immobilized on a conducting surface.[1] Many metal complexes containing single or more catalytic sites have been tested for water oxidation; [2][3][4][5][6][7] however, the design and implementation of a stable and efficient molecular water oxidation system that operates at high catalytic turnover number (TON) and frequency (TOF) for extended periods of controlled-potential electrolysis (CPE), with moderate overpotential and high current density, are challenging. [8][9][10] Herein we disclose robust immobilized [(L 2 bpy)Ir…”

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confidence: 99%

Surface‐Immobilized Single‐Site Iridium Complexes for Electrocatalytic Water Splitting

et al. 2012

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Catalytic water splitting using solar energy represents an attractive potential solution for affordable and renewable energy. [1,2] To construct a (photo)electrochemical H 2 /O 2 evolution system, oxygen evolving catalysts (OECs) need to be immobilized on a conducting surface.[1] Many metal complexes containing single or more catalytic sites have been tested for water oxidation; [2][3][4][5][6][7] however, the design and implementation of a stable and efficient molecular water oxidation system that operates at high catalytic turnover number (TON) and frequency (TOF) for extended periods of controlled-potential electrolysis (CPE), with moderate overpotential and high current density, are challenging. [8][9][10] Herein we disclose robust immobilized [(L 2 bpy)Ir2+ (L is -PO 3 H 2 or -COOH, bpy is 2,2'-bipyridine, Cp* is pentamethylcyclopentadiene) complexes on ITO (indium tin oxide) surface (ITO/Cat) for electrocatalytic water oxidation ( Figure 1). The aqua complexes were obtained by Cl to H 2 O ligand exchange before immobilization on the ITO surfaces. The mono-iridium catalysts are modified with carboxylate and phosphonate linkers that are known to anchor covalently on ITO.[1, 9] At 1.75 V (vs. NHE; NHE = normal hydrogen electrode) the system operates with a high TOF of 6.7 s À1 and has TONs of more than 210 000, well in excess of the maximum TON of 28 000 reported before.[9] The oxygen generation current densities are higher than 1.70 mA cm À2 , which is one to two orders of magnitude higher than the reported densities of approximately 50 mA cm À2 .[ 2+ molecular complex is a highly competent catalytic system for electrochemical oxygen evolution.The synthesis and characterization of the complexes are detailed in the Supporting Information ( Figure S1). [12,13] In situ ligand exchange from Cl to H 2 O and deprotonation are monitored by UV/Vis spectroscopy ( Figure S2 in the Supporting Information). CV of an ITO/Cat.Ir-COOH in aqueous acid (pH 1) shows a catalytic current wave at approximately 1.22 V that sharply grows until approximately 1.31 V, and leads to an O 2 evolution current with tiny oxygen 2+ (Cat.Ir-PO 3 H 2 and Cat.Ir-COOH for L = PO 3 H 2 and COOH, respectively) on ITO for electrochemical water oxidation. The metalstabilizing Cp* ligand is highlighted in brown-red.

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confidence: 99%

Surface‐Immobilized Single‐Site Iridium Complexes for Electrocatalytic Water Splitting

et al. 2012

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“…[10,11] Complex 2 a was isolated in 69 % yield. The 1 H NMR spectrum for the product contained a 1H singlet at d = 6.75 ppm for an a-proton and two doublets of quartets at 4.11 and 4.35 ppm for the now diastereotopic protons of the methylene group at the ethyl ester; these signals indicated that activation of an a-C(sp 3 )ÀH bond had occurred, giving a N-ylide coordinated to iridium through a stereogenic carbon atom, that is, rac-[Cp*Ir(1 a)Cl 2 ] (2 a; Scheme 1).…”

Section: Experimental Investigationsmentioning

confidence: 99%

C(sp³)H Activation without a Directing Group: Regioselective Synthesis of N‐Ylide or N‐Heterocyclic Carbene Complexes Controlled by the Choice of Metal and Ligand

Cross

Razak

Singh

et al. 2014

Chemistry A European J

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N-Ylide complexes of Ir have been generated by C(sp(3))-H activation of α-pyridinium or α-imidazolium esters in reactions with [Cp*IrCl2]2 and NaOAc. These reactions are rare examples of C(sp(3))-H activation without a covalent directing group, which-even more unusually-occur α to a carbonyl group. For the reaction of the α-imidazolium ester [3H]Cl, the site selectivity of C-H activation could be controlled by the choice of metal and ligand: with [Cp*IrCl2]2 and NaOAc, C(sp(3))-H activation gave the N-ylide complex 4; in contrast, with Ag2O followed by [Cp*IrCl2]2, C(sp(2))-H activation gave the N-heterocyclic carbene complex 5. DFT calculations revealed that the N-ylide complex 4 was the kinetic product of an ambiphilic C-H activation. Examination of the computed transition state for the reaction to give 4 indicated that unlike in related reactions, the acetate ligand appears to play the dominant role in C-H bond cleavage.

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“…[78] Allerdings beschränken sich die folgenden Absätze auf Komplexe mit geladenen NHC-Liganden, bei denen Wasserlçslichkeit tatsächlich erwähnt wird. Aus diesem Grund sind die folgenden Berichte gewissermaßen exotisch, da sie zwei Beispiele von Wasserlçslichkeit beschreiben, die aus zusätzlichen Ladungen innerhalb des N-Heterocyclus resultiert, und eine Verçffentlichung die hohe Wasserlçslichkeit eines Nprotonierten NHC darlegt.…”

Section: Funktionalisierung Mit Geladenen Liganden Und Protonenunclassified

Synthese und Anwendung wasserlöslicher NHC‐Übergangsmetall‐Komplexe

et al. 2012

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Dieser Aufsatz gibt eine Übersicht über Übergangsmetallkomplexe mit wasserlöslichen NHC‐Liganden. Bekannte Routen zur Einführung von Wasserlöslichkeit durch gezieltes Ligandendesign werden beleuchtet, und einige allgemeine Eigenschaften wasserlöslicher NHC‐Komplexen werden diskutiert. Die erhöhte Hydrophilie wasserlöslicher Katalysatoren bietet zusätzliche Vorteile für Anwendungen in der Synthese. Neben klassischen Umsetzungen, wie z. B. C‐C‐Kupplungen, umfassen neuere Beispiele von Katalysen mit wasserlöslichen NHC‐Komplexen auch Metathesen und Hydrierungen, in denen sich diese Katalysatoren als besonders leistungsfähig erweisen. Insgesamt ist das Gebiet in weiten Teilen noch unerforscht und hat daher ein großes Potenzial für zukünftige Forschung.

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Katalytische Oxidation von Wasser durch einen Iridiumkomplex mit einem starken Carben‐Donorliganden

Cited by 82 publications

References 70 publications

Surface‐Immobilized Single‐Site Iridium Complexes for Electrocatalytic Water Splitting

Surface‐Immobilized Single‐Site Iridium Complexes for Electrocatalytic Water Splitting

C(sp³)H Activation without a Directing Group: Regioselective Synthesis of N‐Ylide or N‐Heterocyclic Carbene Complexes Controlled by the Choice of Metal and Ligand

Synthese und Anwendung wasserlöslicher NHC‐Übergangsmetall‐Komplexe

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Katalytische Oxidation von Wasser durch einen Iridiumkomplex mit einem starken Carben‐Donorliganden

Cited by 82 publications

References 70 publications

Surface‐Immobilized Single‐Site Iridium Complexes for Electrocatalytic Water Splitting

Surface‐Immobilized Single‐Site Iridium Complexes for Electrocatalytic Water Splitting

C(sp3)H Activation without a Directing Group: Regioselective Synthesis of N‐Ylide or N‐Heterocyclic Carbene Complexes Controlled by the Choice of Metal and Ligand

Synthese und Anwendung wasserlöslicher NHC‐Übergangsmetall‐Komplexe

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C(sp³)H Activation without a Directing Group: Regioselective Synthesis of N‐Ylide or N‐Heterocyclic Carbene Complexes Controlled by the Choice of Metal and Ligand