Metrical Oxidation States of 2-Amidophenoxide and Catecholate Ligands: Structural Signatures of Metal–Ligand π Bonding in Potentially Noninnocent Ligands

2012 ◽  
Vol 51 (3) ◽  
pp. 1251-1260 ◽  
Author(s):  
Seth N. Brown
Keyword(s):  
Oxidation States ◽  
Metal Ligand ◽  
Catecholate Ligands

scholarly journals Iron(II) Complexes Featuring a Redox-Active Dihydrazonopyrrole Ligand

2021 ◽  
Author(s):  
Kate Jesse ◽  
Mu-Chieh Chang ◽  
Alexander S. Filatov ◽  
John Anderson
Keyword(s):  
Redox State ◽  
Oxidation States ◽  
Pincer Ligands ◽  
Detailed Characterization ◽  
Metal Centers ◽  
Redox Couples ◽  
Redox Active ◽  
Secondary Coordination Sphere ◽  
Powerful Strategy ◽  
Metal Ligand

<div>Nature uses control of the secondary coordination sphere</div><div>to facilitate an astounding variety of transformations. Similarly, synthetic chemists have found metal-ligand cooperativity to be a powerful strategy for designing complexes that can mediate challenging reactivity. In particular, this strategy has been used to facilitate two electron reactions with first row transition metals that</div><div>more typically engage in one electron redox processes. While NNN pincer ligands feature prominently in this area, examples which can potentially engage in both proton and electron transfer are less common. Dihydrazonopyrrole (DHP) ligands have been isolated in a variety of redox and protonation states when complexed to Ni. However, the redox-state of this ligand scaffold is less obvious when</div><div>complexed to metal centers with more accessible redox couples. Here, we synthesize a new series of Fe-DHP complexes in two distinct oxidation states. Detailed characterization supports that the redox chemistry</div><div>in this set is still primarily ligand based. Finally, these</div><div>complexes exist as 5-coordinate species with an open coordination site offering the possibility of enhanced reactivity.</div>

scholarly journals Iron(II) Complexes Featuring a Redox-Active Dihydrazonopyrrole Ligand

2021 ◽  
Author(s):  
Kate Jesse ◽  
Mu-Chieh Chang ◽  
Alexander S. Filatov ◽  
John Anderson
Keyword(s):  
Redox State ◽  
Oxidation States ◽  
Pincer Ligands ◽  
Detailed Characterization ◽  
Metal Centers ◽  
Redox Couples ◽  
Redox Active ◽  
Secondary Coordination Sphere ◽  
Powerful Strategy ◽  
Metal Ligand

<div>Nature uses control of the secondary coordination sphere</div><div>to facilitate an astounding variety of transformations. Similarly, synthetic chemists have found metal-ligand cooperativity to be a powerful strategy for designing complexes that can mediate challenging reactivity. In particular, this strategy has been used to facilitate two electron reactions with first row transition metals that</div><div>more typically engage in one electron redox processes. While NNN pincer ligands feature prominently in this area, examples which can potentially engage in both proton and electron transfer are less common. Dihydrazonopyrrole (DHP) ligands have been isolated in a variety of redox and protonation states when complexed to Ni. However, the redox-state of this ligand scaffold is less obvious when</div><div>complexed to metal centers with more accessible redox couples. Here, we synthesize a new series of Fe-DHP complexes in two distinct oxidation states. Detailed characterization supports that the redox chemistry</div><div>in this set is still primarily ligand based. Finally, these</div><div>complexes exist as 5-coordinate species with an open coordination site offering the possibility of enhanced reactivity.</div>

scholarly journals Hydrazine Formation via NiIII-NH2 Radical Coupling in Ni-Mediated Ammonia Oxidation

2020 ◽  
Author(s):  
Nina Gu ◽  
Paul H. Oyala ◽  
Jonas Peters
Keyword(s):  
Water Oxidation ◽  
Ammonia Oxidation ◽  
Bond Formation ◽  
Oxidation States ◽  
Bond Forming ◽  
Radical Coupling ◽  
Multiply Bonded ◽  
Ni Species ◽  
Oxidation Mechanisms ◽  
Metal Ligand

<p>Given the diverse mechanistic possibilities for the overall 6e<sup>-</sup>/6H<sup>+</sup> transformation of ammonia to dinitrogen, identification of M(NH<sub>x</sub>) intermediates involved in N–N bond formation is a central mechanistic challenge. In analogy to water oxidation mechanisms, which widely invoke metal oxo intermediates, metal imide and nitride intermediates have commonly been proposed for ammonia oxidation, and stoichiometric demonstration of N–N bond formation from these metal-ligand multiply bonded species is well-precedented. In contrast, while the homocoupling of M–NH<sub>2</sub> species to form hydrazine has been hypothesized as the key N–N bond forming step in certain molecular ammonia oxidation systems, well-defined examples of this transformation from M–NH<sub>2</sub> complexes are essentially without precedent. This work reports the first example of net ammonia oxidation mediated by a molecular Ni species, a transformation carried out via formal Ni<sup>II</sup>/Ni<sup>III</sup> oxidation states. The available data are consistent with a Ni<sup>III</sup>–NH<sub>2</sub> intermediate featuring substantial spin at N undergoing N–N bond formation to generate a Ni<sup>II</sup><sub>2</sub>(N<sub>2</sub>H<sub>4</sub>) complex. Additional and structurally unusual Ni<sub>x</sub>(N<sub>y</sub>H<sub>z</sub>) species – including a Ni<sub>2</sub>(<i>trans</i>-N<sub>2</sub>H<sub>2</sub>) complex – are characterized and studied as intermediates in the Ni-mediated ammonia oxidation cycle described herein.</p>

scholarly journals Hydrazine Formation via NiIII-NH2 Radical Coupling in Ni-Mediated Ammonia Oxidation

2020 ◽  
Author(s):  
Nina Gu ◽  
Paul H. Oyala ◽  
Jonas Peters
Keyword(s):  
Water Oxidation ◽  
Ammonia Oxidation ◽  
Bond Formation ◽  
Oxidation States ◽  
Bond Forming ◽  
Radical Coupling ◽  
Multiply Bonded ◽  
Ni Species ◽  
Oxidation Mechanisms ◽  
Metal Ligand

<p>Given the diverse mechanistic possibilities for the overall 6e<sup>-</sup>/6H<sup>+</sup> transformation of ammonia to dinitrogen, identification of M(NH<sub>x</sub>) intermediates involved in N–N bond formation is a central mechanistic challenge. In analogy to water oxidation mechanisms, which widely invoke metal oxo intermediates, metal imide and nitride intermediates have commonly been proposed for ammonia oxidation, and stoichiometric demonstration of N–N bond formation from these metal-ligand multiply bonded species is well-precedented. In contrast, while the homocoupling of M–NH<sub>2</sub> species to form hydrazine has been hypothesized as the key N–N bond forming step in certain molecular ammonia oxidation systems, well-defined examples of this transformation from M–NH<sub>2</sub> complexes are essentially without precedent. This work reports the first example of net ammonia oxidation mediated by a molecular Ni species, a transformation carried out via formal Ni<sup>II</sup>/Ni<sup>III</sup> oxidation states. The available data are consistent with a Ni<sup>III</sup>–NH<sub>2</sub> intermediate featuring substantial spin at N undergoing N–N bond formation to generate a Ni<sup>II</sup><sub>2</sub>(N<sub>2</sub>H<sub>4</sub>) complex. Additional and structurally unusual Ni<sub>x</sub>(N<sub>y</sub>H<sub>z</sub>) species – including a Ni<sub>2</sub>(<i>trans</i>-N<sub>2</sub>H<sub>2</sub>) complex – are characterized and studied as intermediates in the Ni-mediated ammonia oxidation cycle described herein.</p>

MicroEXAFS study into the oxidation states of copper coloured Hispano-Moresque lustre decorations

2003 ◽  
Vol 104 ◽  
pp. 519-522 ◽  
Author(s):  
A. D. Smith ◽  
T. Pradell ◽  
J. Molera ◽  
M. Vendrell ◽  
M. A. Marcus ◽  
...  
Keyword(s):  
Oxidation States

Acceptorless amine dehydrogenation and transamination using Pd-doped layered double hydroxides

2018 ◽  
Author(s):  
Diana Ainembabazi ◽  
Nan An ◽  
Jinesh Manayil ◽  
Kare Wilson ◽  
Adam Lee ◽  
...  
Keyword(s):  
Layered Double Hydroxides ◽  
Oxidation States ◽  
Secondary Amines ◽  
Primary Amines ◽  
Acid Dissolution ◽  
Oxidative Amination ◽  
Strong Function ◽  
Excellent Activity ◽  
High Yields ◽  
Double Hydroxides

<div> <p>The synthesis, characterization, and activity of Pd-doped layered double hydroxides (Pd-LDHs) for for acceptorless amine dehydrogenation is reported. These multifunctional catalysts comprise Brønsted basic and Lewis acidic surface sites that stabilize Pd species in 0, 2+, and 4+ oxidation states. Pd speciation and corresponding cataytic performance is a strong function of metal loading. Excellent activity is observed for the oxidative transamination of primary amines and acceptorless dehydrogenation of secondary amines to secondary imines using a low Pd loading (0.5 mol%), without the need for oxidants. N-heterocycles, such as indoline, 1,2,3,4-tetrahydroquinoline, and piperidine, are dehydrogenated to the corresponding aromatics with high yields. The relative yields of secondary imines are proportional to the calculated free energy of reaction, while yields for oxidative amination correlate with the electrophilicity of primary imine intermediates. Reversible amine dehydrogenation and imine hydrogenation determine the relative imine:amine selectivity. Poisoning tests evidence that Pd-LDHs operate heterogeneously, with negligible metal leaching; catalysts can be regenerated by acid dissolution and re-precipitation.</p> </div> <br>

Catalytic Fluorination of Boron Compounds at a Bismuth Redox Platform

2019 ◽  
Author(s):  
Oriol Planas ◽  
Feng Wang ◽  
Markus Leutzsch ◽  
Josep Cornella
Keyword(s):  
Transition Metal ◽  
Main Group ◽  
Group Element ◽  
Oxidation States ◽  
Boron Compounds ◽  
Main Text ◽  
Main Group Element ◽  
Rational Ligand Design ◽  
Supplementary Material

The ability of bismuth to maneuver between different oxidation states in a catalytic redox cycle, mimicking the canonical organometallic steps associated to a transition metal, is an elusive and unprecedented approach in the field of homogeneous catalysis. Herein we present a catalytic protocol based on bismuth, a benign and sustainable main-group element, capable of performing every organometallic step in the context of oxidative fluorination of boron compounds; a territory reserved to transition metals. A rational ligand design featuring hypervalent coordination together with a mechanistic understanding of the fundamental steps, permitted a catalytic fluorination protocol based on a Bi(III)/Bi(V) redox couple, which represents a unique example where a main-group element is capable of outperforming its transition metal counterparts.<br>A main text and supplementary material have been attached as pdf files containing all the methodology, techniques and characterization of the compounds reported.<br>

THE OXIDATION STATES OF IRON AND VOLATILE COMPOSITIONS OF EXPEDITION 352 GLASSES

2019 ◽  
Author(s):  
M. Brounce ◽  
◽  
Mark K. Reagan ◽  
Daniel A. Coulthard ◽  
Katherine A. Kelley ◽  
...  
Keyword(s):  
Oxidation States
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