Biosynthesis of the Iron-Guanylylpyridinol Cofactor of [Fe]-Hydrogenase in Methanogenic Archaea as Elucidated by Stable-Isotope Labeling

Biosynthesis of the Iron-Guanylylpyridinol
Cofactor
of [Fe]-Hydrogenase in Methanogenic Archaea as Elucidated by Stable-Isotope
Labeling:

Journal of the American Chemical Society

DOI: 10.1021/ja211594m

Electrocatalytic Hydrogen Evolution in Acidic Water with Molecular Cobalt Tetraazamacrocycles

Electrocatalytic Hydrogen
Evolution in Acidic Water
with Molecular Cobalt Tetraazamacrocycles:

Journal of the American Chemical Society

DOI: 10.1021/ja210661k

Reversible formal insertion of CO2 into a remote C-H bond of ligand in a Ru(II) complex at room temperature

Reversible formal insertion of CO2 into a remote C-H bond of ligand in a Ru(II) complex at room temperature:

Chem. Commun., 2012, Accepted Manuscript

DOI: 10.1039/C2CC17933D, Communication

Vincent T. Annibale, Datong Song

A reversible formal insertion of CO₂ into a remote C-H bond of the diazafluorenide ligand (L^-) in a Ru(II) complex which occurs at ambient temperature.

MCl2(ampy)(dppf) (M = Ru, Os): Multitasking Catalysts for Carbonyl Compound/Alcohol Interconversion Reactions

MCl2(ampy)(dppf) (M = Ru, Os): Multitasking
Catalysts for Carbonyl Compound/Alcohol Interconversion Reactions:

Barrata et al.

Organometallics DOI: 10.1021/om201189r

Ferrocenes with Perfluorinated Side Chains and Ferrocenophanes with Fluorinated Handles

Ferrocenes with Perfluorinated Side Chains and Ferrocenophanes with Fluorinated Handles:

Lenz et al. Chem Eur J

Trifluorovinyl groups are introduced onto the cyclopentadienyl ligands of ferrocene at the 1-, 1,1′-, and 1,2-positions by Negishi-type and Stille-type coupling reactions of trifluorovinylzinc chloride and tri-n-butyltrifluorovinyl stannane with several iodoferrocenes. Modification of the trifluorovinyl group by nucleophilic substitution and [2+2] cycloaddition make them versatile building blocks for synthetic transformations. 1,1′-Bis(trifluorovinyl) ferrocene reacts upon contact with silica or oxidizing agents and in the presence of a suitable nucleophile through a redox autocatalytic mechanism to afford ferrocenophanes with fluorinated handles. C(F)(H) and C(F)(OMe) moieties in α-positions allowed further modifications to be performed by nucleophilic substitution of the fluorine atoms. A series of ferrocenes with fluorinated side chains and ferrocenophanes with fluorinated handles were isolated and characterized. Several molecular structures were determined by single-crystal X-ray diffraction. The influence of the fluorine substituents on the redox properties of the iron center were studied by cyclic voltammetry.

Tandem Rhodium-Catalyzed Hydroformylation–Hydrogenation of Alkenes by Employing a Cooperative Ligand System

Tandem Rhodium-Catalyzed Hydroformylation–Hydrogenation of Alkenes by Employing a Cooperative Ligand System:

Breit et al. (good theme for seminar or gp meeting). ACIE

Dual action: A multifunctional rhodium catalyst system enables the simultaneous catalysis of two distinct transformations, hydroformylation of an alkene and reduction of an aldehyde, in a highly selective manner. This one-pot/two-step process is controlled by the cooperative action of two different supramolecular ligand systems and transforms terminal alkenes into C₁-chain-elongated linear alcohols.

Versatile Synthesis of PR2NR′2 Ligands for Molecular Electrocatalysts with Pendant Bases in the Second Coordination Sphere

Versatile Synthesis of
PR2NR′2 Ligands
for Molecular Electrocatalysts
with Pendant Bases in the Second Coordination Sphere:

Organometallics

DOI: 10.1021/om201168h

Simplified synthesis of P2N2 macrocycles by Kubiak

[Report] Reversible Reduction of Oxygen to Peroxide Facilitated by Molecular Recognition

[Report] Reversible Reduction of Oxygen to Peroxide Facilitated by Molecular Recognition:

The highly reactive peroxide dianion (O₂^2–) can be captured and stabilized by hydrogen bonding in a molecular box.

Authors: Nazario Lopez, Daniel J. Graham, Robert McGuire Jr., Glen E. Alliger, Yang Shao-Horn, Christopher C. Cummins, Daniel G. Nocera

Cu(I)/O2 Chemistry Using a β-Diketiminate Supporting Ligand Derived from N,N-Dimethylhydrazine: A [Cu3O2]3+ Complex with Novel Reactivity

Cu(I)/O2 Chemistry
Using a β-Diketiminate
Supporting Ligand Derived from N,N-Dimethylhydrazine:
A [Cu3O2]3+ Complex with Novel Reactivity:

Inorganic Chemistry DOI: 10.1021/ic202214c Tolman group

Reduction of TerphenylCo(II) Halide Derivatives inthe Presence of Arenes: Insertion of Co(I) into a C–F Bond

Reduction of Terphenyl
Co(II) Halide Derivatives in
the Presence of Arenes: Insertion of Co(I) into a C–F Bond:

Inorganic Chemistry

DOI: 10.1021/ic202116s

Electrophilic Arene Hydroxylation and Phenol OH Oxidations Performed by an Unsymmetric μ-η1:η1-O2-Peroxo Dicopper(II) Complex

Electrophilic Arene Hydroxylation and Phenol O<img src="http://onlinelibrarystatic.wiley.com/undisplayable_characters/00f8ff.gif" alt="[BOND]">H Oxidations Performed by an Unsymmetric μ-η1:η1-O2-Peroxo Dicopper(II) Complex:

Abstract

Reactions of the unsymmetric dicopper(II) peroxide complex [Cu^II₂(μ-η¹:η¹-O₂)(m-XYL^N3N4)]²⁺ (1 O₂, where m-XYL is a heptadentate N-based ligand), with phenolates and phenols are described. Complex 1 O₂ reacts with p-X-PhONa (X=MeO, Cl, H, or Me) at −90 °C performing tyrosinase-like ortho-hydroxylation of the aromatic ring to afford the corresponding catechol products. Mechanistic studies demonstrate that reactions occur through initial reversible formation of metastable association complexes [Cu^II₂(μ-η¹:η¹-O₂)(p-X-PhO)(m-XYL^N3N4)]⁺ (1 O₂⋅X-PhO) that then undergo ortho-hydroxylation of the aromatic ring by the peroxide moiety. Complex 1 O₂ also reacts with 4-X-substituted phenols p-X-PhOH (X=MeO, Me, F, H, or Cl) and with 2,4-di-tert-butylphenol at −90 °C causing rapid decay of 1 O₂ and affording biphenol coupling products, which is indicative that reactions occur through formation of phenoxyl radicals that then undergo radical CC coupling. Spectroscopic UV/Vis monitoring and kinetic analysis show that reactions take place through reversible formation of ground-state association complexes [Cu^II₂(μ-η¹:η¹-O₂)(X-PhOH)(m-XYL^N3N4)]²⁺ (1 O₂⋅X-PhOH) that then evolve through an irreversible rate-determining step. Mechanistic studies indicate that 1 O₂ reacts with phenols through initial phenol binding to the Cu₂O₂ core, followed by a proton-coupled electron transfer (PCET) at the rate-determining step. Results disclosed in this work provide experimental evidence that the unsymmetric 1 O₂ complex can mediate electrophilic arene hydroxylation and PCET reactions commonly associated with electrophilic Cu₂O₂ cores, and strongly suggest that the ability to form substrate⋅Cu₂O₂ association complexes may provide paths to overcome the inherent reactivity of the O₂-binding mode. This work provides experimental evidence that the presence of a H⁺ completely determines the fate of the association complex [Cu^II₂(μ-η¹:η¹-O₂)(X-PhO(H))(m-XYL^N3N4)]ⁿ⁺ between a PCET and an arene hydroxylation reaction, and may provide clues to help understand enzymatic reactions at dicopper sites.

The way it goes: Reactions of complex [Cu^II₂(μ-η¹:η¹-O₂)(L)]²⁺ (1 O₂) with phenolates and phenols are described (see scheme). Whereas 1 O₂ reacts with PhONa performing tyrosinaselike ortho-hydroxylation of the aromatic ring, its reaction with phenols affords CC coupling products. Mechanistic studies reveal that the presence of a H⁺ completely determines the fate of the association complex [1 O₂-(PhO(H))] between a proton-coupled electron transfer (PCET) and an arene hydroxylation reaction.

ATP-Independent Formation of Hydrocarbons Catalyzed by Isolated Nitrogenase Cofactors

ATP-Independent Formation of Hydrocarbons Catalyzed by Isolated Nitrogenase Cofactors:

Reduce to produce: Molybdenum- and vanadium-nitrogenase cofactors have been isolated and shown to reduce carbon monoxide and cyanide ions to a mixture of alkanes and alkenes in the presence of a strong reductant, europium(II) diethylenetriaminepentaacetate (see scheme). Various hydrocarbons of up to seven carbon atoms in length are detected as products in these ATP-free reactions.

Synthesis of the phosphino-fullerene PPh2(o-C6H4)(CH2NMeCH)C60 and its function as an [small eta]1-P or [small eta]3-P,C2 ligand

Synthesis of the phosphino-fullerene PPh2(o-C6H4)(CH2NMeCH)C60 and its function as an [small eta]1-P or [small eta]3-P,C2 ligand:

Dalton Trans., 2012, Advance Article
DOI: 10.1039/C1DT11769F, Paper

Chia-Hsiang Chen, Chi-Shian Chen, Huei-Fang Dai, Wen-Yann Yeh
A new phosphine-functionalized fullerene molecule has been prepared, which can serve as a hemilabile chelating agent.

our new postdoc's work

Kinetics of oxidation of nitrosodisulfonate anion radical with a metallo-superoxide

Kinetics of oxidation of nitrosodisulfonate anion radical with a metallo-superoxide:

Dalton Trans., 2012, Advance Article DOI: 10.1039/C2DT12019D, Paper

Kaustab Mandal, Rupendranath Banerjee
Cobalt(III)-bound superoxide (1) forms a spin adduct with nitrosodisulfonate anion radical (NDS^2-) and oxidizes it by two electrons. Towards 1, NDS^2- is a kinetically controlled product and its further oxidation lowers the yield.

Synthesis and solvent dependent reactivity of chelating bis-N-heterocyclic carbene complexes of Fe(II) hydrides

Synthesis and solvent dependent reactivity of chelating bis-N-heterocyclic carbene complexes of Fe(II) hydrides:

Dalton Trans., 2012, Advance Article DOI: 10.1039/C2DT12048H, Paper

Sergey Zlatogorsky, Michael J. Ingleson
The synthesis of low coordinate iron(II) hydrides ligated by a chelating bis-N-heterocyclic carbene was complicated by competitive reactions with solvent, reductive elimination of H₂ and/or dissociation of the ligand.

attractive precursor chem

Reaction of an alkyne with dinickel-diphenylsilyl complexes. An emissive disilane formed via the consecutive Si-C and Si-Si bond-making processes

Reaction of an alkyne with dinickel-diphenylsilyl complexes. An emissive disilane formed via the consecutive Si-C and Si-Si bond-making processes:

Chem. Commun.,DOI: 10.1039/C2CC16063C, Communication

Makoto Tanabe, Ryouhei Yumoto, Kohtaro Osakada
The dinickel complex having diphenylsilyl ligands, [{Ni(dmpe)}₂([small mu ]-SiHPh₂)₂], reacted with PhC[triple bond, length as m-dash]CPh to yield a fluorescent dialkenyldisilane via intramolecular Si-Si coupling.

The Ni2H2L4 is a relative of this disilyl compound

Elements of Metabolic Evolution

Elements of Metabolic Evolution:

EJIC

Research into the origin of evolution is polarized between a genetics-first approach, with its focus on polymer replication, and a metabolism-first approach that takes aim at chemical reaction cycles. Taking the latter approach, we explored reductive carbon fixation in a volcanic hydrothermal setting, driven by the chemical potential of quenched volcanic fluids for converting volcanic C1 compounds into organic products by transition-metal catalysts. These catalysts are assumed to evolve by accepting ever-new organic products as ligands for enhancing their catalytic power, which in turn enhances the rates of synthetic pathways that give rise to ever-new organic products, with the overall effect of a self-expanding metabolism. We established HCN, CO, and CH₃SH as carbon nutrients, CO and H₂ as reductants, and iron-group transition metals as catalysts. In one case, we employed the “cyano-system” [Ni(OH)(CN)] with [Ni(CN)₄]²⁻ as the dominant nickel–cyano species. This reaction mainly produced α-amino acids and α-hydroxy acids as well as various intermediates and derivatives. An organo-metal-catalyzed mechanism is suggested that mainly builds carbon skeletons by repeated cyano insertions, with minor CO insertions in the presence of CO. The formation of elemental nickel (Ni⁰) points to an active reduced-nickel species. In another case, we employed the mercapto–carbonyl system [Co₂(CO)₈]/Ca(OH)₂/CO for the double-carbonylation of mercaptans. In a “hybrid system”, we combined benzyl mercaptan with the cyano system, in which [Ni(OH)(CN)] was the most productive for the double-carbon-fixation reaction. Finally, we demonstrated that the addition of products of the cyano system (Gly, Ala) to the hybrid system increased productivity. These results demonstrate the chemical possibility of metabolic evolution through rate-promotion of one synthetic reaction by the products of another.

Combat evolved: The metal-catalyzed reductive conversion of volcanic C1 compounds into organic products is studied under aqueous conditions at high temperatures and high pressures. The detected product mixtures provide evidence for carbon-fixation reactions as potential core pathways for metabolic evolution in a volcanic hydrothermal origin-of-life context.

A Nickel Thiolate Catalyst for the Long-Lived Photocatalytic Production of Hydrogen in a Noble-Metal-Free System

A Nickel Thiolate Catalyst for the Long-Lived Photocatalytic Production of Hydrogen in a Noble-Metal-Free System:

A question of nobility: A biomimetic nickel thiolate complex (see scheme; TEA=triethylamine) exhibits unprecedented activity for the title reaction. By using a low concentration of a sacrificial donor, the system maintains significant activity for at least 60 hours. The enhanced stability of the system is ascribed to the ability to proceed through an oxidative quenching pathway.

This is the complex mentioned by Patrick Holland to our group when we met him last month.

Reversible Protonation of a Thiolate Ligand in an [Fe]-Hydrogenase Model Complex

Reversible Protonation of a Thiolate Ligand in an [Fe]-Hydrogenase Model Complex:

What is the channel? The thiolate ligand in the five-coordinate model complex 1 of [Fe]-hydrogenase is preferentially and reversibly protonated, even in the presence of an acyl ligand. The results suggest that the Cys176 thiolate ligand in [Fe]-hydrogenase can serve as the internal base to accept the proton after heterolytic splitting of H₂.

Ni(SR)4

Synthesis, molecular structure and supramolecular chemistry of a new nickel-quinoxaline dithiolate system [Bu4N]2[Ni(6,7-qdt)2] (6,7-qdt = quinoxaline-6,7-dithiolate) and comparison of its electronic and electrochemical properties with those of [Bu4N]2[Ni(qdt)2] (qdt = quinoxaline-2,3-dithiolate) Pages 809-813 in Inorganic Communications Ramababu Bolligarla, Gummadi Durgaprasad, Samar K. Das

Purchase

Graphical Abstract

A new nickel bis(dithiolene) complex has been synthesized based on quinoxaline-6,7-dithiolate. ► Its crystal structure has been characterized by C–H···S and C–H···N weak interactions. ► The title compound undergoes reversible oxidation at a very low oxidation potential.

The quinoxalinedithiolates have an internal base and this bis(dithiolene)Ni could be a good building block.

Synthesis, structural characterization and electrochemical studies of [Fe2(μ-L)(CO)6] and [Fe2(μ-L)(CO)5(PPh3)] (L = pyrazine-2,3-dithiolate, quinoxaline-2,3-dithiolate and pyrido[2,3-b]pyrazine-2,3-dithiolate): Towards modeling the active site of[FeFe]–Hydrogenase

Synthesis, structural characterization and electrochemical studies of [Fe2(μ-L)(CO)6] and [Fe2(μ-L)(CO)5(PPh3)] (L = pyrazine-2,3-dithiolate, quinoxaline-2,3-dithiolate and pyrido[2,3-b]pyrazine-2,3-dithiolate): Towards modeling the active site of[FeFe]–Hydrogenase: Publication year: 2011
Source: Journal of Organometallic Chemistry, In Press, Accepted Manuscript, Available online 20 June 2011
Gummadi, Durgaprasad , Ramababu, Bolligarla , Samar K., Das
The reaction of heterocyclic 1,2-ene-dithiol ligands, namely, pyrazine-2,3-dithiol (H2pydt), quinoxaline-2,3-dithiol (H2qdt) and pyrido[2,3-b]pyrazine-2,3-dithiol (H2ppdt) with Fe2(CO)9 yields the ‘[FeFe]–hydrogenase’ model complexes [Fe2{μ-pydt}(CO)6] (1), [Fe2{μ-qdt}(CO)6] (2) and [Fe2{μ-ppdt}(CO)6] (3), respectively. Highlights: ► Reaction of heterocyclic 1,2-ene-dithiols with Fe2(CO)9 yields the title complexes. ► These compounds further react with PPh3 to form mono-PPh3-substituted derivatives. ► The system shows relatively low reduction potentials among related model compounds. ► Electro-catalytic hydrogen generation has been demonstrated.

Co2(CO)6(μ,η2-HCCFc) as Precursor in the Synthesisof Multiredox Cyclicand Linear Vinylferrocenylsiloxanes

Co2(CO)6(μ,η2-HCCFc) as Precursor in the Synthesis
of Multiredox Cyclic
and Linear Vinylferrocenylsiloxanes:

Organometallics

DOI: 10.1021/om201018h

this Co2CO6L2 platform is v versatile

Photoelectrochemical Hydrogen Generation by an [FeFe] Hydrogenase Active Site Mimic at a p-Type Silicon/Molecular Electrocatalyst Junction

Photoelectrochemical Hydrogen Generation by an [FeFe] Hydrogenase Active Site Mimic at a p-Type Silicon/Molecular Electrocatalyst Junction:

Let there be light! A dithiolate-bridged [FeFe] complex with structural features of the [FeFe] hydrogenase active site has been photoelectrochemically reduced by a p-type Si photocathode at a potential 500 mV less negative compared with a glassy carbon electrode (see figure). In the presence of HClO₄, hydrogen generation has been achieved at a photovoltage of 600 mV with a (105±5) % Faradaic efficiency.

Chem. Eur. J.

The Shrinking World of Innocent Ligands: Conventionaland Non-Conventional Redox-Active Ligands

The Shrinking World of Innocent Ligands: Conventionaland Non-Conventional Redox-Active Ligands:

Abstract

This essay for EurJIC's cluster issue on cooperative and redox non-innocent ligands introduces the reader to redox-active ligands, which range from the small archetypical NO^+/•/– and O₂^{0/•–/2–}systems via the classical 1,4-dihetero-1,3-diene chelates (e.g. α-diimine, dithiolene, or o-quinone redox series) to π-conjugated macrocycles. The increased attention paid recently to the redox activity of ligands in coordination chemistry has now prompted wider successful searches, resulting in the establishing of less-conventional examples such as cyanide, carbon monoxide, thioethers, or acetylacetonate derivatives as non-innocently behaving ligands. By considering situations with significantly covalent metal–ligand bonding, the cases of metal–oxo, metal–hydrido, and organometallic compounds will also be addressed, with a perspective on how pervasive non-innocent ligand behavior is. The materials and reactivity potential of redox-active ligands will be pointed out.

Evidence for non-innocent ligand behavior is being found for an increasing number of coordination compounds, including those with seemingly unassuming ligands. The recognition of such situations can be exploited for supporting attractive material properties and for understanding and developing chemical reactivity.

Electron-Transfer Reduction of Dinuclear Copper Peroxo and Bis-μ-oxo Complexes Leading to the Catalytic Four-Electron Reduction of Dioxygen to Water

Electron-Transfer Reduction of Dinuclear Copper Peroxo and Bis-μ-oxo Complexes Leading to the Catalytic Four-Electron Reduction of Dioxygen to Water:

Abstract

The four-electron reduction of dioxygen by decamethylferrocene (Fc*) to water is efficiently catalyzed by a binuclear copper(II) complex (1) and a mononuclear copper(II) complex (2) in the presence of trifluoroacetic acid in acetone at 298 K. Fast electron transfer from Fc* to 1 and 2 affords the corresponding Cu^I complexes, which react at low temperature (193 K) with dioxygen to afford the η²:η²-peroxo dicopper(II) (3) and bis-μ-oxo dicopper(III) (4) intermediates, respectively. The rate constants for electron transfer from Fc* and octamethylferrocene (Me₈Fc) to 1 as well as electron transfer from Fc* and Me₈Fc to 3 were determined at various temperatures, leading to activation enthalpies and entropies. The activation entropies of electron transfer from Fc* and Me₈Fc to 1 were determined to be close to zero, as expected for outer-sphere electron-transfer reactions without formation of any intermediates. For electron transfer from Fc* and Me₈Fc to 3, the activation entropies were also found to be close to zero. Such agreement indicates that the η²:η²-peroxo complex (3) is directly reduced by Fc* rather than via the conversion to the corresponding bis-μ-oxo complex, followed by the electron-transfer reduction by Fc* leading to the four-electron reduction of dioxygen to water. The bis-μ-oxo species (4) is reduced by Fc* with a much faster rate than the η²:η²-peroxo complex (3), but this also leads to the four-electron reduction of dioxygen to water.

Catalytic reduction of dioxygen: Two copper complexes that act as efficient catalysts for the four-electron four-proton reduction of O₂ by Fc* in the presence of trifluoroacetic acid in acetone have been prepared and characterized. The roles of the η²:η²-peroxo and bis-μ-oxo intermediates in the catalytic four-electron reduction of O₂ to water have been clarified (see figure).

Chem Eur J

Divergent Carbonylation Reactivity Preferences of Nickel Complexes Containing Amido Pincer Ligands: Migratory Insertion versus Reductive Elimination

Divergent Carbonylation
Reactivity Preferences
of Nickel Complexes Containing Amido Pincer Ligands: Migratory Insertion
versus Reductive Elimination:

Organometallics

DOI: 10.1021/om201041z

Tuning of Redox Potentials by Introducing a Cyclometalated Bond to Bis-tridentate Ruthenium(II) Complexes Bearing Bis(N-methylbenzimidazolyl)benzene or -pyridine Ligands

Tuning of Redox Potentials
by Introducing a Cyclometalated
Bond to Bis-tridentate Ruthenium(II) Complexes Bearing Bis(N-methylbenzimidazolyl)benzene or -pyridine Ligands:

Inorganic Chemistry

DOI: 10.1021/ic2016885

Crowded Diphosphinomethane Ligands in Catalysis: [(R2PCH2PR′2-κ2P)NiR″]+ Cations for Ethylene Polymerization without Activators

Crowded Diphosphinomethane
Ligands in Catalysis: [(R2PCH2PR′2-κ2P)NiR″]+ Cations for Ethylene
Polymerization without Activators:

Organometallics

DOI: 10.1021/om200715w

The structures of P2NiCl2 and P2Ni(R)2 are beautifully square-planar, whereas the dppm which is familiar to our group is not able to make square-planar complexes. This ligand might be useful for our modelling chemistry.

Incorporation of an n-Butylsulfonate Functionality To Induce Aqueous Solubility on Ruthenium(II) η6-Arene Complexes

Incorporation of an n-Butylsulfonate
Functionality To Induce Aqueous Solubility on Ruthenium(II) η6-Arene Complexes:

Organometallics DOI: 10.1021/om2005595

Preorganized Frustrated Lewis Pairs

Preorganized Frustrated Lewis Pairs:

Journal of the American Chemical Society DOI: 10.1021/ja210214r

Crystallographic Snapshots of the Bond-Breaking Isomerization Reactions Involving Nickel(II) Complexes with Hemilabile Ligands

Crystallographic Snapshots of the Bond-Breaking Isomerization Reactions Involving Nickel(II) Complexes with Hemilabile Ligands:

Freeze-frame: Octahedral and square-planar structural isomers, representing the two “end states” in a hemilabile ligand bond-breaking isomerization reaction, have been characterized in solution by spectroscopic methods and in the solid state by X-ray crystallography (see picture: Ni green, C gray, P orange, N blue, S yellow).

Well-Defined Heterometallic and Unsymmetric M2O2 Complexes Arising from Binding and Activation of O2

Well-Defined Heterometallic and Unsymmetric M2O2 Complexes Arising from Binding and Activation of O2:

AbstractOxygen binding and activation reactions at dimetal sites constitute chemical processes of fundamental interest, because of the implication of these reactions in biology, chemical synthesis, and catalysis. This account collects and discusses studies of O₂ binding and/or activation by inequivalent dimetal sites, and it specially focuses on systems in which O₂-bound reaction intermediates have been experimentally characterized. Homometallic unsymmetric systems and heterometallic complexes are reviewed, and their chemistry in oxidative transformations is described. Introduction of asymmetry into M₂O₂ cores poses important challenges to their preparation, and strategies developed to address this problem are discussed. Distinct spectroscopic and chemical properties emerge from these unsymmetric systems.

Oxygen binding and activation at unsymmetric and heterometallic complexes by well-defined MO₂M′ species is reviewed. Studies described so far have provided evidence for a rich chemistry. Novel spectroscopic properties, electronic structures and reactivities are emerging, and they suggest a myriad of fresh avenues still to be explored.

Ruthenium Hydride Complexes with Zwitterionic Quinonoid Ligands – Isomer Separation, Structural Properties, Electrochemistry, and Catalysis

Ruthenium Hydride Complexes with Zwitterionic Quinonoid Ligands – Isomer Separation, Structural Properties, Electrochemistry, and Catalysis:

Reactions of [Ru(PPh₃)₃(CO)(H)Cl] with the zwitterionic p-benzoquinonemonoimine-type ligands 4-(n-butylamino)-6-(n-butylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q¹), 4-(isopropylamino)-6-(isopropylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q²), and 4-(benzylamino)-6-(benzylimino)-3-oxocyclohexa-1,4-dien-1-olate (Q³) in the presence of a base led to the formation of mononuclear complexes [Ru(PPh₃)₂(CO)(H)(Q¹_–H)] (1a and 1b), [Ru(PPh₃)₂(CO)(H)(Q²_–H)] (2a and 2b), and [Ru(PPh₃)₂(CO)(H)(Q³_–H)] (3a and 3b), respectively. The positional isomers (a and b) that were formed in each case were separated by preparative TLC. The structural characterization of 2a and 3a·MeCN helped to identify the isomers, and established the distorted octahedral coordination geometry around the ruthenium center. The bond lengths in the complexes are consistent with localization of the double bonds in Q²_–H and Q³_–H in both their monodeprotonated and metal-coordinated forms. The Ru–C–O(carbonyl) bond angle is almost linear. Cyclic voltammetry of the complexes showed one oxidation and one reduction process. These are predominantly centered on the quinonoid ligands, which shows their redox-noninnocent character. Studies of transfer hydrogenation with 2a as a precatalyst showed that, in the presence of KOH, acetophenone could be converted to 1-phenylethanol within 10 h in over 90 % yield.

Ruthenium hydride complexes derived from zwitterionic quinonoid ligands have been synthesized, and their isomers have been separated and structurally characterized. Cyclic voltammetry of the complexes showed the redox noninnocent nature of the quinonoid ligands. One of the complexes showed good activity as a catalyst for the transfer hydrogenation of acetophenone.

EJIC

Thiolato-Bridged Arene–Ruthenium Complexes: Synthesis, Molecular Structure, Reactivity, and Anticancer Activity of the Dinuclear Complexes [(arene)2Ru2(SR)2Cl2]

Thiolato-Bridged Arene–Ruthenium Complexes: Synthesis, Molecular Structure, Reactivity, and Anticancer Activity of the Dinuclear Complexes [(arene)2Ru2(SR)2Cl2]:

Treatment of an arene–ruthenium dichloride dimer with thiols RSH to lead to cationic trithiolato complexes of the type [(arene)₂Ru₂(SR)₃]⁺ was shown to proceed through the neutral thiolato complexes [(arene)₂Ru₂(SR)₂Cl₂], which have been isolated and characterized for arene = p-MeC₆H₄iPr and R = CH₂Ph (1), CH₂CH₂Ph (2), CH₂C₆H₄-p-tBu (3), and C₆H₁₁ (4). The single-crystal X-ray structure analysis of the p-tert-butylbenzyl derivative 3 reveals that the two ruthenium atoms are bridged by the two thiolato ligands without a metal–metal bond. The neutral dithiolato complexes[(arene)₂Ru₂(SR)₂Cl₂] (1–3) are intermediates in the formation of the cationic trithiolato complexes [(arene)₂Ru₂(SR)₃]⁺ (5–7). Of the new [(arene)₂Ru₂(SR)₂Cl₂] complexes, derivative 2 is highly cytotoxic against human ovarian cancer cells, with IC₅₀ values of 0.20 μM for the A2780 cell line and 0.31 for the cisplatin-resistant cell line A2780cisR.

Treatment of p-cymene–ruthenium dichloride dimer with aliphatic thiols to give cationic trithiolato–diruthenium complexes was shown to proceed through the intermediacy of the corresponding neutral dithiolato complexes.

Raja!

Acid-Induced Degradation of Phosphorescent Dopants for OLEDs and Its Application to the Synthesis of Tris-heteroleptic Iridium(III) Bis-cyclometalated Complexes

Acid-Induced Degradation of Phosphorescent Dopants for OLEDs and Its Application to the Synthesis of Tris-heteroleptic
Iridium(III) Bis-cyclometalated Complexes:

Inorganic Chemistry DOI: 10.1021/ic202162q

Easy way to introduce luminescence into our systems, cleave mu-Cl dimer with pdt monomer.

Manganese Carbonyls Bearing Tripodal Polypyridine Ligands as Photoactive Carbon Monoxide-Releasing Molecules

Manganese Carbonyls Bearing Tripodal Polypyridine Ligands as Photoactive Carbon Monoxide-Releasing Molecules:

Inorganic Chemistry DOI: 10.1021/ic2021287

Related to Chris Letko's ligands

Synthesis, Cu(II) complexation, 64Cu-labeling and biological evaluation of cross-bridged cyclam chelators with phosphonate pendant arms

Synthesis, Cu(II) complexation, 64Cu-labeling and biological evaluation of cross-bridged cyclam chelators with phosphonate pendant arms:

Dalton Trans., 2012, Advance Article DOI: 10.1039/C1DT11743B

Riccardo Ferdani, Dannon J. Stigers, Ashley L. Fiamengo, Lihui Wei, Barbara T. Y. Li, James A. Golen, Arnold L. Rheingold, Gary R. Weisman, Edward H. Wong, Carolyn J. Anderson
New phosphonate-pendant-armed cross-bridged cyclams have been synthesized and conveniently radiolabeled with ⁶⁴Cu at room temperature.

an unusual and versatile ligand framework for controlling two adjacent sites

Merging the old with the new

Biomimetic chemistry: Merging the old with the new

• Marcetta Y. Darensbourg
• & Ryan D. Bethel

• The classic organometallic compound ferrocene has been combined with a unique diiron unit in the latest synthetic analogue of an enzyme active site, achieving the three functionalities needed for a working model of diiron hydrogenase, itself of ancient origin.

Highlight of Camara's Nature Chemistry written by MYD in Nature Chemistry