Oxidatively Induced Reactivity of [Fe2(CO)4(κ2-dppe)(μ-pdt)]: an Electrochemical and Theoretical Study of the Structure Change and Ligand Binding Processes

Oxidatively Induced Reactivity of [Fe2(CO)4(κ2-dppe)(μ-pdt)]:
an Electrochemical and Theoretical Study of the Structure Change and Ligand Binding Processes

by Dounia Chouffai, Giuseppe Zampella, Jean-François Capon, Luca De Gioia, Frédéric Gloaguen, François Y. Pétillon, Philippe Schollhammer and Jean Talarmin

Inorganic Chemistry DOI: 10.1021/ic201601q

Regioselectivity of H Cluster Oxidation

Regioselectivity of H Cluster Oxidation: by Marta K. Bruska, Martin T. Stiebritz and Markus Reiher

Journal of the American Chemical Society DOI: 10.1021/ja209165r

A Valence Bond Description of Dizwitterionic Dithiolene Character in an Oxomolybdenum–Bis(dithione) Complex

A Valence Bond Description of Dizwitterionic Dithiolene Character in an Oxomolybdenum–Bis(dithione) Complex:

Abstract

Metallodithiolene non-innocence is explored in an oxomolybdenum–bis(dithione) complex, [Mo⁴⁺O(iPr₂Pipdt)₂Cl][PF₆] (where Pipdt is N,N′-piperazine-2,3-dithione), which has a piperazine ring as an integral part of the dithiolene ligand. The title complex displays spectroscopic features that are unusual for a formally reduced Mo^IV–dithiolene complex, namely a low-energy metal-to-ligand charge-transfer band with appreciable intensity and C–C and C–S stretching frequencies that are markedly different from those of oxomolybdenum complexes coordinated to dianionic dithiolene ligands. The electronic structure of the ligand has been described in valence bond terms as a resonance hybrid of dithione and dizwitterionic dithiolene structures.

Metallodithiolene non-innocence is explored in [Mo⁴⁺O(iPr₂Pipdt)₂Cl][PF₆] (Pipdt: N,N′-piperazine-2,3-dithione), which possesses a piperazine ring as an integral part of the dithiolene ligand and displays unusual spectroscopic features for a formally reduced Mo^IV–dithiolene complex. The electronic structure of the ligand can be described in valence bond terms as a resonance hybrid of dithione and dizwitterionic dithiolene.

Cooperative Aliphatic PNP Amido Pincer Ligands – Versatile Building Blocks for Coordination Chemistry and Catalysis

Cooperative Aliphatic PNP Amido Pincer Ligands – Versatile Building Blocks for Coordination Chemistry and Catalysis:

Abstract

In this review, the coordination chemistry of electron-rich metal complexes with the simple aliphatic, anionic diphosphanylamido ligand {N(CH₂CH₂PR₂)₂}^– is covered and compared with other commonly used, anionic PEP (E = C, N) pincer ligands. The strong π-basicity of this ligand enables both the stabilization of electronically and coordinatively highly unsaturated complexes and their use as cooperating ligands in bifunctional stoichiometric bond activation reactions and catalysis. Versatile ligand backbone dehydrogenation gives access to related enamido and dienamido ligands {(R₂PCHCH)N(CH₂CH₂PR₂)}^– and {N(CHCHPR₂)₂}^–, respectively. This oxidative functionalization enables fine-tuning of the ligand donor properties and thereby of the structural features, electronic structure, and reactivity of the respective complexes, which is discussed for several examples.

Aliphatic PNP pincer ligands, HN(CH₂CH₂PR₂)₂, and ligands derived from them by backbone functionalization, are versatile chelating ligands for metal–ligand cooperative small molecule activation and catalysis. This microreview covers the recent work with these ligands and provides a comprehensive comparison with related pincer systems.

Vanadium nitrogenase: A two-hit wonder?

Vanadium nitrogenase: A two-hit wonder?:

Dalton Trans., 2012, Advance Article
DOI: 10.1039/C1DT11535A, Perspective

Yilin Hu, Chi Chung Lee, Markus W. Ribbe
V-nitrogenase is not only capable of reducing N₂ to NH₃, but also capable of reducing CO to hydrocarbons.
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Unexpected Direct Reduction Mechanism for Hydrogenation of Ketones Catalyzed by Iron PNP Pincer Complexes

Unexpected Direct Reduction
Mechanism for Hydrogenation
of Ketones Catalyzed by Iron PNP Pincer Complexes:

Inorganic Chemistry

DOI: 10.1021/ic2020176

Double Metalation of Acetone by a Nickel–NHC Complex: Trapping of an Oxyallyl Ligand at a Dinickel Center

Double Metalation of Acetone
by a Nickel–NHC
Complex: Trapping of an Oxyallyl Ligand at a Dinickel Center:

Organometallics DOI: 10.1021/om200819c

We are making CpNi(NHC)Cl in our course

[Brevia] Evidence for Interstitial Carbon in Nitrogenase FeMo Cofactor

Evidence for Interstitial Carbon in Nitrogenase FeMo Cofactor: Structural data show that the light atom at the center of the nitrogenase active site cofactor is a carbon.

Authors: Thomas Spatzal, Müge Aksoyoglu, Limei Zhang, Susana L. A. Andrade, Erik Schleicher, Stefan Weber, Douglas C. Rees, Oliver Einsle

Hydrogen Production Coupled to Hydrocarbon Oxygenation from Photocatalytic Water Splitting

Hydrogen Production Coupled to Hydrocarbon Oxygenation from Photocatalytic Water Splitting:

On the sunny side: A homogeneous system for H₂ production and hydrocarbon oxidation was developed in the absence of any sacrificial reagent. This system consists of [Ru(TPA)(H₂O)₂]²⁺ and [Fe₃(CO)₁₂] as catalysts and [Ru(bpy)₃]²⁺ and [Ir(bpy)(ppy)₂]⁺ as photosensitizers (PS). Water is the oxygen source as well as the source for H₂ formation (see picture; Sub=organic substrate).

Structural basis for a [4Fe-3S] cluster in the oxygen-tolerant membrane-bound [NiFe]-hydrogenase

Structural basis for a [4Fe-3S] cluster in the oxygen-tolerant membrane-bound [NiFe]-hydrogenase:

Structural basis for a [4Fe-3S] cluster in the oxygen-tolerant membrane-bound [NiFe]-hydrogenase

Nature 479, 7372 (2011). doi:10.1038/nature10504

Authors: Yasuhito Shomura, Ki-Seok Yoon, Hirofumi Nishihara & Yoshiki Higuchi

Membrane-bound respiratory [NiFe]-hydrogenase (MBH), a H2-uptake enzyme found in the periplasmic space of bacteria, catalyses the oxidation of dihydrogen: H2 → 2H+ + 2e− (ref. 1). In contrast to the well-studied O2-sensitive [NiFe]-hydrogenases (referred to as the standard enzymes), MBH has an O2-tolerant H2 oxidation activity; however, the mechanism of O2 tolerance is unclear. Here we report the crystal structures of Hydrogenovibrio marinus MBH in three different redox conditions at resolutions between 1.18 and 1.32 Å. We find that the proximal iron-sulphur (Fe-S) cluster of MBH has a [4Fe-3S] structure coordinated by six cysteine residues—in contrast to the [4Fe-4S] cubane structure coordinated by four cysteine residues found in the proximal Fe-S cluster of the standard enzymes—and that an amide nitrogen of the polypeptide backbone is deprotonated and additionally coordinates the cluster when chemically oxidized, thus stabilizing the superoxidized state of the cluster. The structure of MBH is very similar to that of the O2-sensitive standard enzymes except for the proximal Fe-S cluster. Our results give a reasonable explanation why the O2 tolerance of MBH is attributable to the unique proximal Fe-S cluster; we propose that the cluster is not only a component of the electron transfer for the catalytic cycle, but that it also donates two electrons and one proton crucial for the appropriate reduction of O2 in preventing the formation of an unready, inactive state of the enzyme.

The crystal structure of an oxygen-tolerant hydrogenase uncovers a novel iron-sulphur centre

The crystal structure of an oxygen-tolerant hydrogenase uncovers a novel iron-sulphur centre:

The crystal structure of an oxygen-tolerant hydrogenase uncovers a novel iron-sulphur centre

Nature 479, 7372 (2011). doi:10.1038/nature10505

Authors: Johannes Fritsch, Patrick Scheerer, Stefan Frielingsdorf, Sebastian Kroschinsky, Bärbel Friedrich, Oliver Lenz & Christian M. T. Spahn

Hydrogenases are abundant enzymes that catalyse the reversible interconversion of H2 into protons and electrons at high rates. Those hydrogenases maintaining their activity in the presence of O2 are considered to be central to H2-based technologies, such as enzymatic fuel cells and for light-driven H2 production. Despite comprehensive genetic, biochemical, electrochemical and spectroscopic investigations, the molecular background allowing a structural interpretation of how the catalytic centre is protected from irreversible inactivation by O2 has remained unclear. Here we present the crystal structure of an O2-tolerant [NiFe]-hydrogenase from the aerobic H2 oxidizer Ralstonia eutropha H16 at 1.5 Å resolution. The heterodimeric enzyme consists of a large subunit harbouring the catalytic centre in the H2-reduced state and a small subunit containing an electron relay consisting of three different iron-sulphur clusters. The cluster proximal to the active site displays an unprecedented [4Fe-3S] structure and is coordinated by six cysteines. According to the current model, this cofactor operates as an electronic switch depending on the nature of the gas molecule approaching the active site. It serves as an electron acceptor in the course of H2 oxidation and as an electron-delivering device upon O2 attack at the active site. This dual function is supported by the capability of the novel iron-sulphur cluster to adopt three redox states at physiological redox potentials. The second structural feature is a network of extended water cavities that may act as a channel facilitating the removal of water produced at the [NiFe] active site. These discoveries will have an impact on the design of biological and chemical H2-converting catalysts that are capable of cycling H2 in air.

Visible light-driven CO2 reduction by enzyme coupled CdS nanocrystals

Visible light-driven CO2 reduction by enzyme coupled CdS nanocrystals:

Chem. Commun., 2012, Advance Article DOI: 10.1039/C1CC16107E, Communication

Yatendra S. Chaudhary, Thomas W. Woolerton, Christopher S. Allen, Jamie H. Warner, Elizabeth Pierce, Stephen W. Ragsdale, Fraser A. Armstrong

Carbon monoxide dehydrogenase (CODH) co-attached with CdS nanocrystals (quantum dots or nanorods) exhibits fast CO₂ reduction under visible light.

(Metallocenylphosphane)palladium Dichlorides – Synthesis, Electrochemistry and Their Application in C–C Coupling Reactions

(Metallocenylphosphane)palladium Dichlorides – Synthesis, Electrochemistry and Their Application in C–C Coupling Reactions:

AbstractThe synthesis and characterization of a series of metallocenylphosphanes of the type PR₂Mc/Se=PR₂Mc [Mc = Fc = Fe(η⁵-C₅H₄)(η⁵-C₅H₅), R = C₆H₅ (3a/4a), 2-MeC₆H₄ (3b/4b), c-C₄H₃O (3c/4c), tBu (3d/4d), c-C₆H₁₁ (3e/4e); Mc = Rc = Ru(η⁵-C₅H₄)(η⁵-C₅H₅), R = C₆H₅ (6a/7a), 2-MeC₆H₄ (6b/7b), c-C₄H₃O (6c/7c), c-C₆H₁₁ (6d/7d)] and their palladium complexes [PdCl₂(PR₂Mc)₂] [Mc = Fc, R = C₆H₅ (9a), 2-MeC₆H₄ (9b), c-C₄H₃O (9c), tBu (9d), c-C₆H₁₁ (9e); Mc = Rc, R = C₆H₅ (10a), 2-MeC₆H₄ (10b), c-C₄H₃O (10c), c-C₆H₁₁ (10d)] is reported. The solid-state structure of 4b confirms the tetrahedrally distorted geometry at phosphorus with the o-tolyl groups indicating steric congestion, which is confirmed by ¹H and ¹³C{¹H} NMR spectroscopy. Phosphanes 3, 4, and 9 were characterized by cyclic voltammetry with [N(nBu)₄][B(C₆F₅)₄] as the supporting electrolyte. In general, the first oxidation occurs at the phosphane metallocenyl unit(s), although the appropriate Pd complexes are oxidized at more positive potentials. Depending on the phosphane or selenophosphane, follow-up reactions occur, which are discussed. In contrast, the palladium complexes show reversible redox behavior. UV/Vis/NIR spectroelectrochemical studies carried out on 9b indicate an electrostatic interaction between the two terminal ferrocenyl groups. All of the palladium complexes were examined as catalysts in Heck and Suzuki C–C cross-coupling and showed high catalytic activities. These results can be correlated to the electronic (¹J) parameters of the selenophosphanes.

Evidence for acyl-iron ligation in the active site of [Fe]-hydrogenase provided by mass spectrometry and infrared spectroscopy

Evidence for acyl-iron ligation in the active site of [Fe]-hydrogenase provided by mass spectrometry and infrared spectroscopy:

Dalton Trans., 2012, Advance ArticleDOI: 10.1039/C1DT11093D, Paper

Seigo Shima, Michael Schick, Jorg Kahnt, Kenichi Ataka, Klaus Steinbach, Uwe Linne
MS and IR analyses provided strong evidence for the acyl-iron ligation in the iron guanylylpyridinol cofactor of [Fe]-hydrogenase.

Separation of Metal Binding and Electron Transfer Sites as a Strategy To Stabilize the Ligand-Reduced and Metal-Oxidized Form of [Mo(CO)4L]

Separation of Metal Binding
and Electron Transfer
Sites as a Strategy To Stabilize the Ligand-Reduced and Metal-Oxidized
Form of [Mo(CO)4L]:

OrganometallicsDOI: 10.1021/om2007858 Wolfgang Kaim

Transfer Hydrogenation in Water via a Ruthenium Catalyst with OH Groups near the Metal Center on a bipy Scaffold

Transfer Hydrogenation
in Water via a Ruthenium Catalyst
with OH Groups near the Metal Center on a bipy Scaffold:

Organometallics DOI: 10.1021/om200638p

[Report] N2 Reduction and Hydrogenation to Ammonia by a Molecular Iron-Potassium Complex

[Report] N2 Reduction and Hydrogenation to Ammonia by a Molecular Iron-Potassium Complex: A molecular iron complex offers insights into the industrial iron catalyst used to split nitrogen to make ammonia.

Authors: Meghan M. Rodriguez, Eckhard Bill, William W. Brennessel, Patrick L. Holland

Photorelease of Primary Aliphatic and Aromatic Amines by Visible-Light-Induced Electron Transfer

Photorelease of Primary Aliphatic and Aromatic Amines by Visible-Light-Induced Electron Transfer:

Organic Letters DOI: 10.1021/ol202456d

A phosphino-oxazoline ligand as a P,N-bridge in palladium/cobalt or P,N-chelate in nickel complexes: catalytic ethylene oligomerization

A phosphino-oxazoline ligand as a P,N-bridge in palladium/cobalt or P,N-chelate in nickel complexes: catalytic ethylene oligomerization:

Dalton Trans., 2011, Advance Article DOI: 10.1039/C1DT11352F, Paper

Shuanming Zhang, Roberto Pattacini, Suyun Jie, Pierre Braunstein
Using a P,N-phosphino-oxazoline ligand, the Pd(II)/Co(II) zwitterionic complex [{PdCl(1)}⁺([small mu ]-1)(CoCl₃)^-] (2) and octahedral Ni(II) complexes were obtained, the latter show reversible solvent-dependent isomerism between all-trans-3 and all-cis-4.

possible Ni precursors for NiFe models

The Conversion of Nickel-Bound CO into an Acetyl Thioester: Organometallic Chemistry Relevant to the Acetyl Coenzyme A Synthase Active Site

The Conversion of Nickel-Bound CO into an Acetyl Thioester: Organometallic Chemistry Relevant to the Acetyl Coenzyme A Synthase Active Site:

When three become one: Within one nickel-based model system, the three reactants CO, MeI, and PhSH have been assembled to yield an acetyl thioester. The reactivity is of relevance for the functioning of the acetyl coenzyme A synthase active site and provides insights into possible binding sequences.