Ligand Redox Activity and Mixed Valency in First-Row Transition-Metal Complexes Containing Tetrachlorocatecholate and Radical Tetrachlorosemiquinonate Ligands

Ligand Redox Activity and Mixed Valency in First-Row Transition-Metal Complexes Containing Tetrachlorocatecholate and Radical Tetrachlorosemiquinonate Ligands:

Inorganic Chemistry

DOI: 10.1021/ic201237d

Electrochemical Water Oxidation with Cobalt-Based Electrocatalysts from pH 0–14: The Thermodynamic Basis for Catalyst Structure, Stability, and Activity

Electrochemical Water Oxidation with Cobalt-Based Electrocatalysts from pH 0–14: The Thermodynamic Basis for Catalyst Structure, Stability, and Activity:

Journal of the American Chemical Society

DOI: 10.1021/ja205647m

The Cause for Tremendous Acceleration of Chloride Substitution via Base Catalysis in the Chloro Pentaammine Cobalt(III) Ion

The Cause for Tremendous Acceleration of Chloride Substitution via Base Catalysis in the Chloro Pentaammine Cobalt(III) Ion:

Inorganic Chemistry DOI: 10.1021/ic102034n

Although only theory, the mechanism is of importance to our group related to transfer hydrogenation and stabilization of unsaturation by pi-donors

Model Study of CO Inhibition of [NiFe]hydrogenase

Model Study of CO Inhibition of [NiFe]hydrogenase:

Inorganic Chemistry

DOI: 10.1021/ic200965t

We present a model study, using a NiRu H₂ase mimic, that demonstrates that (i) CO completely inhibits the catalytic cycle of the model compound, (ii) CO prefers to coordinate to the Ru^II center rather than taking an axial position on the Ni^II center, and (iii) CO is unable to displace a hydrido ligand from the NiRu center. We combine these studies with a reevaluation of previous studies to propose that, under normal circumstances, CO inhibits [NiFe]H₂ase by complexing to the Fe^II center.

Iron(II) template synthesis of benzannulated triphospha- and triarsamacrocycles

Iron(II) template synthesis of benzannulated triphospha- and triarsamacrocycles:

Dalton Trans., 2011, Advance Article
DOI: 10.1039/C0DT01724H, Paper

Thomas Albers, Julia Baker (nee Johnstone), Simon J. Coles, Peter G. Edwards, Benson Kariuki, Paul D. Newman
New 9-membered benzannulated tridentate phosphorus and arsenic macrocycles are formed in high yield by the base promoted nucleophilic displacement of F^- in 2-fluorophenyl phosphines on a CpFe⁺ template.
To cite this article before page numbers are assigned, use the DOI form of citation above.
The content of this RSS Feed (c) The Royal Society of Chemistry

Bis(acetylacetonato)ruthenium Complexes of Noninnocent 1,2-Dioxolene Ligands: Qualitatively Different Bonding in Relation to Monoimino and Diimino Analogues

Bis(acetylacetonato)ruthenium Complexes of Noninnocent 1,2-Dioxolene Ligands: Qualitatively Different Bonding in Relation to Monoimino and Diimino Analogues:

Abstract

Coordination compounds [Ru(acac)₂(Q)] (acac=acetylacetonate; Q=o-benzoquinone) were prepared as complexes 1 (Q=o-benzoquinone), 2 (Q=3-methoxy-o-benzoquinone), 3 (Q=4-methyl-o-benzoquinone), and 4 (Q=3,5-di-tert-butyl-o-benzoquinone). The structures of 1 and 2 were determined to reveal a Ru^III/o-benzosemiquinone formulation, supported by analysis of experimental data (spectroscopy, magnetism of 1) and by DFT calculations. The S=1 ground state calculated for 1 stands in contrast to the spin-paired analogues with arylimino-o-benzosemiquinonato and diimino-o-benzoquinone ligands. The close contacts of about 5.3 Å possible between semiquinone O atoms of different molecules in the crystal allow for intermolecular spin–spin interactions and an overall complex magnetic behavior. One quasireversible oxidation and two reversible one-electron reductions yielded the corresponding molecular ions, which were characterized by UV-visible-NIR and EPR spectroelectrochemistry in terms of [Ru^III(acac)₂(Q⁰)]⁺, [Ru^III(acac)₂(Q²⁻)]⁻, and [Ru^II(acac)₂(Q²⁻)]²⁻ descriptions in agreement with DFT results. The use of acceptor-substituted 1,2-dioxolenes resulted in the isolation of ionic species Na[Ru(acac)₂(Q)] (Na(5); Q=4-chloro-o-benzoquinone) and Na(6) (Q=4-nitro-o-benzoquinone), which were similarly investigated as compounds 1–4. Magnetic susceptibility and EPR results confirm an S= ground state based on ruthenium(III). The combined studies reveal a remarkable substituent sensitivity, and in comparison to recently analyzed Ru(acac)₂ complexes with o-benzoquinone monoimine and diimine ligands, the all-O-donor-containing new systems are distinguished by a qualitatively different metal–ligand interaction based on closer intermolecular radical–radical contacts and on weaker intramolecular dπ–π* interactions.

Noninnocence and experience: Weak intramolecular metal–ligand interaction and close intermolecular semiquinone–semiquinone contacts result in a complex paramagnetism of [Ru^III(acetylacetonate)₂(Q^.−)] (see figure), which can further undergo reduction and oxidation. This behavior contrasts with the diamagnetism established for monoimino and diimino analogues.

ICBIC15: Feeling jaded?

ICBIC15: Feeling jaded?

Greetings from Vancouver, where I am attending ICBIC15 – the international conference on bio-inorganic chemistry. As the name suggests, this is the 15th instalment of this series of conferences…or is it? There have been quite a few mentions of a mysterious ‘ICBIC zero’, which happened 35 years ago, also here at the University of British Columbia in Vancouver. Chris Orvig, the chair, showed us the programme from that meeting during his welcome address – as organizer, he was interested to see that there were no times for any of the talks, just ‘morning’ or ‘afternoon’! The only speaker at that conference who is also speaking this year is (no prizes for guessing) Harry Gray, who is quite a godfather of this field.

He’s not the only godfather though, and many long-standing members of this quite friendly community are giving jade anniversary lectures, to celebrate the 35 years passed since ‘ICBIC 0’. These jade lectures aren’t the plenaries, however: these are being given by speakers who have never given plenaries at an ICBIC before. All this adds up to a pretty good mix, because there have been some excellent plenaries from speakers at the younger end of the spectrum.

There is a bit of drawback to these lectures (and not just that the conference programme has been printed black and white, so the jade lectures don’t stand out like they do in the PDF): the difficulty of trying to fit a lot of work into just 20 or 30 minutes! After complimenting Ed Solomon on doing well to keep to his 20 minute slot, Harry Gray said he was going to go one better and fit 35 years of work on electron transfer in proteins into 3 slides! He just about managed…

One of the jade lectures that I enjoyed the most was from Karl Wieghardt, and he almost managed to get through his whole talk without moving past the title slide! He was talking in the radical enzymes and non-innocent ligands sessions and certainly convinced me that bipyridine and terpyridine aren’t anywhere near as innocent as people think. Terpyridine in particular can take on four electrons and thus have five different oxidation states and a variety of spin states. Although that’s not what it says in Cotton & Wilkinson, it’s what the X-ray data and DFT calculations suggest.

As this is quite a distinct and friendly community, I’m going to leave the last word to Harry Gray. In his talk he mentioned that the two most important reactions in the world are photosynthesis and respiration. As he said, they’re both firmly in the bio-inorganic field…so tell that to the organic chemists!

Neil

Neil Withers (Associate Editor, Nature Chemistry)

Palladium(II) Hydrido Complexes Having a Primary Silyl or Germyl Ligand: Synthesis, Crystal Structures, and Dynamic Behavior

Organometallics

DOI: 10.1021/om200576f

We have wondered about Pd-H-Fe(CO)3 models

Selective Homogeneous Hydrogenation of Biogenic Carboxylic Acids with [Ru(TriPhos)H]+: A Mechanistic Study

Journal of the American Chemical Society

DOI: 10.1021/ja2034377

potentially useful for biomass

A Robust, Air-Stable, Reusable Ruthenium Catalyst for Dehydrogenation of Ammonia Borane

A Robust, Air-Stable, Reusable Ruthenium Catalyst for Dehydrogenation of Ammonia Borane:

Journal of the American Chemical Society

DOI: 10.1021/ja2058154

Synthesis, cis/trans Isomerization, and Reactivity of Palladium Alkyl Complexes That Contain a Chelating N-Heterocyclic-Carbene Sulfonate Ligand

Synthesis, cis/trans Isomerization, and Reactivity of Palladium Alkyl Complexes That Contain a Chelating N-Heterocyclic-Carbene Sulfonate Ligand:

Organometallics

DOI: 10.1021/om200482a

our new postdoc

Rhodium-catalyzed asymmetric addition of arylboroxines to [small beta]-alkoxyacrylate esters

Chem. Commun., 2011, Advance Article
DOI: 10.1039/C1CC14150C, Communication

Takahiro Nishimura, Atsuyuki Kasai, Makoto Nagaosa, Tamio Hayashi
Asymmetric addition of arylboroxines to [small beta]-alkoxyacrylate esters proceeded in the presence of a rhodium/chiral diene complex to give [small beta]-alkoxy-[small beta]-arylcarboxylic acid esters with very high enantioselectivity.

Fc does nothing. This group specializes in chiral dienes as asymmetric spectator ligands

Secondary Ferrocenyl Phosphines: Versatile Precursors for the Synthesis of Bi- and Tridentate Ligands

Togni et al.

Organometallics

DOI: 10.1021/om200574k
Perhaps we could make redox-active diphosphines similarly

Transition Metal–Alkane σ-Complexes with Oxygen Donor Co-ligands

These are some of the best and simplest examples of agostic complexes (no chelation required).
Grahame Ball and Tony Hill
Journal of the American Chemical Society

DOI: 10.1021/ja203470y

"

A Reactive Ru–Binaphtholate Building Block with Self-Tuning Hapticity

Journal of the American Chemical Society

DOI: 10.1021/ja204767a

"

Pt(II)-activated coupling of aminoethylferrocene with benzonitrile. A facile access route to a new redox-active bis(ferrocenyl-amidine) anion sensor

Chem. Commun., 2011, Advance Article
DOI: 10.1039/C1CC13704B, Communication

Daniel Nieto, Ana M^a Gonzalez-Vadillo, Sonia Bruna, Cesar J. Pastor, Angel E. Kaifer, Isabel Cuadrado
A new redox-active bis(ferrocenyl-amidine) H₂PO₄^- anion sensor has been prepared via Pt(II)-mediated nucleophilic addition of [small beta]-aminoethylferrocene to a benzonitrile ligand.

Normal and inverted redox potentials and structural changes tuned by medium effects in [M2Mo(C5Me5)2(S2C6H4)2(CO)2] (M = Co, Rh)

Chem. Sci., 2011, Advance Article
DOI: 10.1039/C1SC00272D, Edge Article

Satoshi Muratsugu, Keitaro Sodeyama, Fusao Kitamura, Satoru Tsukada, Mizuki Tada, Shinji Tsuneyuki, Hiroshi Nishihara
Redox potential inversion tuned by medium effect was observed in the reduction of heterometal trinuclear metalladithiolene complexes.

potential inversion is a way to get 2e transfer at one potential

Hydrogen is an energy source for hydrothermal vent symbioses

Nature 476, 7359 (2011). doi:10.1038/nature10325
Jillian M. Petersen, Frank U. Zielinski, Thomas Pape, Richard Seifert, Cristina Moraru, Rudolf Amann, Stephane Hourdez, Peter R. Girguis, Scott D. Wankel, Valerie Barbe, Eric Pelletier, Dennis Fink, Christian Borowski, Wolfgang Bach & Nicole Dubilier

The discovery of deep-sea hydrothermal vents in 1977 ... We propose that the ability to use hydrogen as an energy source is widespread in hydrothermal vent symbioses, particularly at sites where hydrogen is abundant.

Comment at Nature 476, 7359 (2011). doi:10.1038/476154a
A commentary on the Nature paper. 
(The commentaries are often better or easier to read than the original paper)

The Coordination Behaviour of Ferrocene-based Pyridylphosphine Ligands towards AgI and AuI

Z. anorg. allgem. Chem.
Abstract. The reaction of the P,N-ligands [Fe(C₅H₄-PPh₂)(C₅H₄-2-py)] (1) (2-py = pyrid-2-yl), [Fe(C₅H₄-PPh₂)(C₅H₄-CH₂-2-py)] (2) and [Fe(C₅H₄-PPh₂)(C₅H₄-3-py)] (3) (3-py = pyrid-3-yl) with Ag[BF₄] in a 1:1 stoichiometric ratio afforded complexes of the type [Ag(L)][BF₄] (L = 1–3), which were structurally characterised by X-ray diffraction. Two structure types were observed in the solid state, viz. coordination polymer (L = 1, 2) and cyclic dimer (L = 2, 3). The reaction of1–3 with one equivalent of [AuCl(tht)] (tht = tetrahydrothiophene) afforded complexes of the type [AuCl(L-κP)] (L = 1–3), whose crystal structures were determined by X-ray diffraction. Their reactions with one equivalent of Ag[BF₄] gave products of the general composition [Au(L)][BF₄]; of these the cyclic dimer {[Au(μ-1)][BF₄]}₂ wasstructurally characterised by X-ray diffraction. The P,N,P-ligandC₅H₃N-2,6-(fcPPh₂)₂ (4, fc = 1,1′-ferrocenediyl) was synthesised by Negishi cross-coupling of Ph₂PfcZnCl with 2,6-dibromopyridine. Its crystal structure was determined by X-ray diffraction. The reaction of 4 with two equivalents of [AuCl(tht)] afforded the dinuclear gold(I) complex [(AuCl)₂(μ-4-κ²P,P)]. The mononuclear gold(I) complex [Au(4-κ²P,P)][SbF₆] was obtained in a one-pot reaction of 4 with one equivalent of [AuCl(tht)] and subsequently with one equivalent of Ag[SbF₆]; it contains 4 in a trans-chelating binding mode, as revealed by a crystal structure determination."

Redox Non-Innocence of Thioether Crowns: Spectroelectrochemistry and Electronic Structure of Formal Nickel(III) Complexes of Aza–Thioether Macrocycles

The Ni^II complexes [Ni([9]aneNS₂-CH₃)₂]²⁺ ([9]aneNS₂-CH₃=N-methyl-1-aza-4,7-dithiacyclononane), [Ni(bis[9]aneNS₂-C₂H₄)]²⁺ (bis[9]aneNS₂-C₂H₄=1,2-bis-(1-aza-4,7-dithiacyclononylethane) and [Ni([9]aneS₃)₂]²⁺ ([9]aneS₃=1,4,7-trithiacyclononane) ... X-ray structure of [Ni^III([9]aneNS₂-CH₃)₂](ClO₄)₆⋅(H₅O₂)₃ reveals an octahedral ... multi-frequency X-, L-, S-, K-band EPR spectra of the 3+ cations  reveals delocalisation of charge onto the S-thioether centres. EPR spectra for [⁶¹Ni([9]aneS₃)₂]³⁺ are consistent with a dynamic Jahn–Teller distortion in this compound.