Oct 30, 2012

Coincorporation of N andTa into TiO2 Nanowiresfor Visible Light Driven Photoelectrochemical Water Oxidation

Coincorporation of N and
Ta into TiO2 Nanowires
for Visible Light Driven Photoelectrochemical Water Oxidation
:
TOC Graphic
The Journal of Physical Chemistry C
DOI: 10.1021/jp309743u

Electrical Control ofOptical Plasmon Resonance withGraphene

Electrical Control of
Optical Plasmon Resonance with
Graphene
:
TOC Graphic
Nano Letters
DOI: 10.1021/nl302656d

Symmetrical Hydrogen Bondsin Iridium(III) Alkoxideswith Relevance to Outer Sphere Hydrogen Transfer

Symmetrical Hydrogen Bonds in Iridium(III) Alkoxides with Relevance to Outer Sphere Hydrogen Transfer:
TOC Graphic
Inorganic Chemistry
DOI: 10.1021/ic301601c

Detailed ElectrochemicalStudies of the TetrarutheniumPolyoxometalate Water Oxidation Catalyst in Acidic Media: Identificationof an Extended Oxidation Series using Fourier Transformed AternatingCurrent Voltammetry

Detailed Electrochemical Studies of the Tetraruthenium Polyoxometalate Water Oxidation Catalyst in Acidic Media: Identification of an Extended Oxidation Series using Fourier Transformed Aternating Current Voltammetry:
TOC Graphic
Inorganic Chemistry
DOI: 10.1021/ic301370y

Catalytic desulfitative homocoupling of sodium arylsulfinates in water using PdCl2 as the recyclable catalyst and O2 as the terminal oxidant

Catalytic desulfitative homocoupling of sodium arylsulfinates in water using PdCl2 as the recyclable catalyst and O2 as the terminal oxidant:
Green Chem., 2012, Accepted Manuscript
DOI: 10.1039/C2GC36550B, Paper
Bin Rao, Weixi Zhang, Lan Hu, Meiming Luo
A green and convenient approach to symmetrical biaryls has been developed. The catalytic desulfitative homocoupling of various inexpensive and readily available sodium arylsulfinates in environment-friendly solvent-water and under clean oxidant-molecular...
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Ru-Zn supported on hydroxyapatite as effective catalysts for partial hydrogenation of benzene

Ru-Zn supported on hydroxyapatite as effective catalysts for partial hydrogenation of benzene:
Green Chem., 2012, Accepted Manuscript
DOI: 10.1039/C2GC36596K, Paper
Buxing Han, Peng Zhang, Tianbin Wu, Tao Jiang, Weitao Wang, Huizhen Liu, Honglei Fan, Zhaofu Zhang
Design and preparation of efficient and greener catalytic systems for partial hydrogenation of benzene to cyclohexene is an interesting topic in green chemistry. In this work, Ru and Ru-Zn catalysts...
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Selective oxidation of alcohols and aldehydes over supported metal nanoparticles

Selective oxidation of alcohols and aldehydes over supported metal nanoparticles:
Green Chem., 2012, Advance Article
DOI: 10.1039/C2GC36441G, Critical Review
Sara E. Davis, Matthew S. Ide, Robert J. Davis
Selective oxidation reactions will likely play an important role in the development of biorefineries. The use of heterogeneous catalysts with molecular oxygen offers a more environmentally benign route than traditional oxidation processes. This review explores the oxidation mechanism and compares reaction rates over a variety of metal catalysts.
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Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols with the Liberation of Syngas

Iridium-Catalyzed Dehydrogenative Decarbonylation of Primary Alcohols with the Liberation of Syngas:

Abstract

A new iridium-catalyzed reaction in which molecular hydrogen and carbon monoxide are cleaved from primary alcohols in the absence of any stoichiometric additives has been developed. The dehydrogenative decarbonylation was achieved with a catalyst generated in situ from [Ir(coe)2Cl]2 (coe=cyclooctene) and racemic 2,2′-bis(diphenylphosphino)-1,1′-binaphthyl (rac-BINAP) in a mesitylene solution saturated with water. A catalytic amount of lithium chloride was also added to improve the catalyst turnover. The reaction has been applied to a variety of primary alcohols and gives rise to products in good to excellent yields. Ethers, esters, imides, and aryl halides are stable under the reaction conditions, whereas olefins are partially saturated. The reaction is believed to proceed by two consecutive organometallic transformations that are catalyzed by the same iridium(I)–BINAP species. First, dehydrogenation of the primary alcohol to the corresponding aldehyde takes place, which is then followed by decarbonylation to the product with one less carbon atom.
Thumbnail image of graphical abstract
Step on the syngas! An iridium catalyst promotes two transformations in the same pot by cleaving both molecular hydrogen and carbon monoxide from primary alcohols (see scheme). The reaction does not require any stoichiometric additives and tolerates a variety of functional groups.

Chem. Eur. J.

A Biomimetic Pathway for Vanadium-Catalyzed Aerobic Oxidation of Alcohols: Evidence for a Base-Assisted Dehydrogenation Mechanism

A Biomimetic Pathway for Vanadium-Catalyzed Aerobic Oxidation of Alcohols: Evidence for a Base-Assisted Dehydrogenation Mechanism:

Abstract

The first step in the catalytic oxidation of alcohols by molecular O2, mediated by homogeneous vanadium(V) complexes [LVV(O)(OR)], is ligand exchange. The unusual mechanism of the subsequent intramolecular oxidation of benzyl alcoholate ligands in the 8-hydroxyquinolinato (HQ) complexes [(HQ)2VV(O)(OCH2C6H4-p-X)] involves intermolecular deprotonation. In the presence of triethylamine, complex 3 (X=H) reacts within an hour at room temperature to generate, quantitatively, [(HQ)2VIV(O)], benzaldehyde (0.5 equivalents), and benzyl alcohol (0.5 equivalents). The base plays a key role in the reaction: in its absence, less than 12 % conversion was observed after 72 hours. The reaction is first order in both 3 and NEt3, with activation parameters ΔH=(28±4) kJ mol−1 and ΔS=(−169±4) J K−1 mol−1. A large kinetic isotope effect, 10.2±0.6, was observed when the benzylic hydrogen atoms were replaced by deuterium atoms. The effect of the para substituent of the benzyl alcoholate ligand on the reaction rate was investigated using a Hammett plot, which was constructed using σp. From the slope of the Hammett plot, ρ=+(1.34±0.18), a significant buildup of negative charge on the benzylic carbon atom in the transition state is inferred. These experimental findings, in combination with computational studies, support an unusual bimolecular pathway for the intramolecular redox reaction, in which the rate-limiting step is deprotonation at the benzylic position. This mechanism, that is, base-assisted dehydrogenation (BAD), represents a biomimetic pathway for transition-metal-mediated alcohol oxidations, differing from the previously identified hydride-transfer and radical pathways. It suggests a new way to enhance the activity and selectivity of vanadium catalysts in a wide range of redox reactions, through control of the outer coordination sphere.
Thumbnail image of graphical abstract
Biomimetic aerobic oxidation of alcohols, as catalyzed by an (8-hydroxyquinolinato)vanadium complex, is promoted by Brønsted bases, which deprotonate the alcoholato ligand and thereby induce electronic reorganization (see scheme). This base-assisted dehydrogenation resembles certain metalloenzyme-catalyzed oxidations, in which a base situated near the active site participates directly in the redox reaction.

Chem. Eur. J.

Oct 29, 2012

Hydrogen shuttling: synthesis and reactivity of a 14-electron iridium complex featuring a bis(alkyl) tethered N-heterocyclic carbene ligand

Hydrogen shuttling: synthesis and reactivity of a 14-electron iridium complex featuring a bis(alkyl) tethered N-heterocyclic carbene ligand:
Chem. Commun., 2012, Accepted Manuscript
DOI: 10.1039/C2CC35947B, Communication
Simon Aldridge
This is an Accepted Manuscript, which has been through the RSC Publishing peer review process and has been accepted for publication. Accepted manuscripts are published online shortly after acceptance. This version of the article will be replaced by the fully edited, formatted and proof read Advance Article as soon as this is available.
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Proton-Electron Transfer Pathways in the Reactions of Peroxyl and dpph[round bullet, filled] Radicals with Hydrogen-Bonded Phenols

Proton-Electron Transfer Pathways in the Reactions of Peroxyl and dpph[round bullet, filled] Radicals with Hydrogen-Bonded Phenols:
Chem. Commun., 2012, Accepted Manuscript
DOI: 10.1039/C2CC36531F, Communication
Riccardo Amorati, Stefano Menichetti, Caterina Viglianisi, Mario Foti
The kinetics of the reaction of peroxyl and dpph[round bullet, filled] radicals with phenols H-bonded with N-bases have been studied for the first time. Electron-transfer processes are observed in MeCN but only...
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Dependence of the oxygen reduction reaction at sol-gel derived Co-based catalysts on acidic solution pH and temperature

Dependence of the oxygen reduction reaction at sol-gel derived Co-based catalysts on acidic solution pH and temperature: Publication year: 2012
Source:Journal of Electroanalytical Chemistry
A. Mani, V.I. Birss
This work is focused on the oxygen reduction reaction (ORR) at non-precious metal catalysts formed using a modified sol-gel (SG) synthesis approach, in which carbon and nitrogen were added in the form of either ethylenediamine (en) or 1,2-phenylenediamine (pda)) to a pre-formed Co oxide gel. It was confirmed that the Co-pda-derived material, when heat-treated at 900 °C, is a much better ORR catalyst than the analogous en-derived material, heat-treated to its optimum of 700 °C, giving an activity about 10-11 times higher and a lower H2O2 yield. The ORR was examined over a range of acidic solutions (all at room temperature and an oxygen pressure of 1 atmosphere). For both catalysts, the reaction rate was found to be independent of the H+ concentration at pH < 2.5, with the Co-pda and -en catalysts giving a transfer coefficient of ca. 1 and 0.5-0.7, respectively. At pH > 2.5, an unusual pH response was seen, suggestive of the development of local pH conditions inside the catalyst layer. While the catalysts were stable only to solution temperatures of ca. 55 °C, the ORR activation energy in the kinetic (Eact = 34 kJ/mol) and diffusion controlled (Eact = 8.8 kJ/mol) regions could still be determined. Based on all of these results, a possible mechanism for the ORR at below and above pH 2.5, for both the Co-pda and Co-en catalysts, was proposed.

Highlights

► The Co-pda-derived material (900 °C) is a better ORR catalyst than the Co-en-derived material (700 °C). ► The Co-pda-derived catalyst, the transfer coefficient (α) is ∼1 and no pH dependence of the ORR rate at pH < 2.6. ► A possible mechanism for the ORR at pH < and > 2.6 was presented. ► The ORR was examined as a function of solution temperature (12-62 °C). ► It was also found that the catalyst was unstable at solution temperatures above around 50 °C.

Detection of Unusual ReactionIntermediates during the Conversion of W(N2)2(dppe)2 to W(H)4(dppe)2 and of H2O into H2

Detection of Unusual Reaction
Intermediates during the Conversion of W(N2)2(dppe)2 to W(H)4(dppe)2 and of H2O into H2
:
TOC Graphic
Journal of the American Chemical Society
DOI: 10.1021/ja302202q

Inhibition of Charge Disproportionationof MnO2 Electrocatalysts for Efficient Water Oxidationunder NeutralConditions

Inhibition of Charge Disproportionation
of MnO2 Electrocatalysts for Efficient Water Oxidation
under Neutral
Conditions
:
TOC Graphic
Journal of the American Chemical Society
DOI: 10.1021/ja306499n

Oct 26, 2012

Ruthenium-Catalyzed ortho-Alkylation of Phenols with Alcohols by Dehydrative Coupling

Ruthenium-Catalyzed ortho-Alkylation of Phenols with Alcohols by Dehydrative Coupling: Thumbnail image of graphical abstract
Only water: Phenols have been shown to undergo a ruthenium-catalyzed ortho-alkylation reaction (see scheme; Cy=cyclohexyl). Unactivated alcohols are used as the alkylating agents and water is the only by-product that is generated, making this transformation more atom-economical and greener than traditional methods.

Identification and Characterization of the “Super-Reduced” State of the H-Cluster in [FeFe] Hydrogenase: A New Building Block for the Catalytic Cycle?

Identification and Characterization of the “Super-Reduced” State of the H-Cluster in [FeFe] Hydrogenase: A New Building Block for the Catalytic Cycle?: Thumbnail image of graphical abstract
Super-reduced and super-active: A new redox state in the active site of algal [FeFe] hydrogenases has been identified and characterized by EPR and FTIR spectroscopy. Electrochemical and in vitro essays show that this species is highly active in hydrogen production and suggest that it is a key intermediate in the catalytic cycle of all [FeFe] hydrogenases.

Rationalizing the 1.9 Å Crystal Structure of Photosystem II—A Remarkable Jahn–Teller Balancing Act Induced by a Single Proton Transfer

Rationalizing the 1.9 Å Crystal Structure of Photosystem II—A Remarkable Jahn–Teller Balancing Act Induced by a Single Proton Transfer: Thumbnail image of graphical abstract
Balancing act: DFT calculations show that the structures of the water-oxidizing complex in the two most recent single crystal XRD studies of photosystem II at 2.9 Å and 1.9 Å resolution are tautomers related by a single proton transfer. The anomalous oxygen species, O(5), weakly bound to four metal centers in the 1.9 Å structure (see picture) is identified as a substrate water molecule balanced between the Jahn–Teller axes of Mn(1), Mn(3), and Mn(4).

Oct 23, 2012

Iridium Complexes of BulkyCCC-Pincer N-HeterocyclicCarbene Ligands: Steric Control of Coordination Number and CatalyticAlkene Isomerization

Iridium Complexes of Bulky
CCC-Pincer N-Heterocyclic
Carbene Ligands: Steric Control of Coordination Number and Catalytic
Alkene Isomerization
:
TOC Graphic
Organometallics
DOI: 10.1021/om300468d

Hydrogen storage and evolution catalysed by metal hydride complexes

Hydrogen storage and evolution catalysed by metal hydride complexes:
Dalton Trans., 2012, Advance Article
DOI: 10.1039/C2DT31823G, Perspective
Shunichi Fukuzumi, Tomoyoshi Suenobu
Hydrogen storage and evolution were catalysed by [C,N] and [C,C] cyclometalated iridium hydride complexes in water at ambient temperature under atmospheric pressure.
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Structural and reactivity comparison of analogous organometallic Pd(III) and Pd(IV) complexes

Structural and reactivity comparison of analogous organometallic Pd(III) and Pd(IV) complexes:
Dalton Trans., 2012, Advance Article
DOI: 10.1039/C2DT32127K, Communication
Fengzhi Tang, Fengrui Qu, Julia R. Khusnutdinova, Nigam P. Rath, Liviu M. Mirica
Isolation of analogous Pd(III) and Pd(IV) complexes allows an unprecedented structural and reactivity comparison of the two high-valent oxidation states.
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Electrochemical Behavior and Dioxygen Reactivity of Tripodal Dinuclear Copper Complexes Linked by Unsaturated Rigid Spacers

Electrochemical Behavior and Dioxygen Reactivity of Tripodal Dinuclear Copper Complexes Linked by Unsaturated Rigid Spacers:
Dalton Trans., 2012, Accepted Manuscript
DOI: 10.1039/C2DT31456H, Paper
Yves Le Mest, Francoise Conan, Antoine Gomila, Nicolas Le Poul, Jean-Michel Kerbaol, Nathalie Cosquer, Smail Triki, Benedicte Douziech
New dinucleating ligands based on two tripodal tris(2-pyridylmethyl)amine (TMPA) units linked by a series of delocalized [capital Pi]-electrons spacers have been synthesized. Their di-CuII complexes have been prepared and structurally characterized....
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A highly stable polypyridyl-based cobalt catalyst for homo- and heterogeneous photocatalytic water reduction

A highly stable polypyridyl-based cobalt catalyst for homo- and heterogeneous photocatalytic water reduction:
Dalton Trans., 2012, Accepted Manuscript
DOI: 10.1039/C2DT31699D, Communication
Roger Alberto, Peter Hamm, Miguel Guttentag, Alexander Rodenberg, Cyril Bachmann, Anna Senn
Synthesis, characterization and activity in homogenous photocatalytic hydrogen production of a cobalt polypyridyl complex are reported. TONs up to 30'000 H2/Co could be achieved. Immobilization of the complex on a...
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Constructing manmade enzymes for oxygen activation

Constructing manmade enzymes for oxygen activation:
Dalton Trans., 2013, Advance Article
DOI: 10.1039/C2DT32010J, Perspective
Craig T. Armstrong, Daniel W. Watkins, J. L. Ross Anderson
Here we describe how current understanding of natural oxygen-activating enzymes can inform the design and construction of manmade oxygenase enzymes.
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Tridentate Cobalt complexes as alternate redox couples for high efficiency Dye Sensitized Solar Cells

Tridentate Cobalt complexes as alternate redox couples for high efficiency Dye Sensitized Solar Cells:
Chem. Sci., 2012, Accepted Manuscript
DOI: 10.1039/C2SC21401F, Edge Article
Ben Aribia Kais, Thomas Moehl, Shaik M Zakeeruddin, Michael Gratzel
Cobalt terpyridine complexes could rival the classical triiodide/iodide redox couple as efficient alternate redox couples for the dye-sensitized solar cells. The cobalt bis-2,2',6',2''-terpyridine complexes enable systematic tuning of the redox...
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