scholarly journals Flexibility of the CueR Metal Site Probed by Instantaneous Change of Element and Oxidation State from Ag I to Cd II

2020 ◽  
Vol 26 (33) ◽  
pp. 7451-7457
Author(s):  
Ria K. Balogh ◽  
Béla Gyurcsik ◽  
Mikael Jensen ◽  
Peter W. Thulstrup ◽  
Ulli Köster ◽  
...  
Keyword(s):  
Oxidation State ◽  
Instantaneous Change ◽  
Metal Site

Chromium oxidation state mapping in human cells

2003 ◽  
Vol 104 ◽  
pp. 289-292 ◽  
Author(s):  
R. Ortega ◽  
B. Fayard ◽  
M. Salomé ◽  
G. Devès ◽  
J. Susini
Keyword(s):  
Oxidation State ◽  
Human Cells ◽  
Chromium Oxidation

LOCAL SYMMETRY AT THE 3d METAL SITE AND CHEMICAL ORDER IN AMORPHOUS AND CRYSTALLINE Ni1-xBx

1985 ◽  
Vol 46 (C8) ◽  
pp. C8-217-C8-221 ◽  
Author(s):  
M. Maurer ◽  
A. Mehdaoui ◽  
J. M. Friedt
Keyword(s):  
Local Symmetry ◽  
Chemical Order ◽  
Metal Site

Radiation of electromagnetic waves on instantaneous change of the state of the radiating system

1978 ◽  
Vol 126 (10) ◽  
pp. 311-321 ◽  
Author(s):  
Boris M. Bolotovskii ◽  
Valerii A. Davydov ◽  
V.E. Rok
Keyword(s):  
Electromagnetic Waves ◽  
The State ◽  
Instantaneous Change

A Short Synthesis of (+)-Brefeldin C via Enantioselective Radical Hydroalkynylation

2019 ◽  
Author(s):  
Lars Gnägi ◽  
Severin Vital Martz ◽  
Daniel Meyer ◽  
Robin Marc Schärer ◽  
Philippe Renaud
Keyword(s):  
Total Synthesis ◽  
Natural Product ◽  
Oxidation State ◽  
Single Step ◽  
Radical Process ◽  
Target Molecule ◽  
Short Synthesis ◽  
The One

<div><div><div><div><p>A very concise total synthesis of (+)-brefeldin C starting from 2-furanylcyclopentene is described. This approach is based on an unprecedented enantioselective radical hydroalkynylation process to introduce the two cyclopentane stereocenters in a single step. The use of a furan substituent allows to achieve a high trans diastereoselectivity during the radical process and it contains the four carbon atoms C1–C4 of the natural product in an oxidation state closely related to the one of the target molecule. The eight-step synthesis require six product purifications and it provides (+)-brefeldin C in 18% overall yield.</p></div></div></div></div>

Piperazine as an Inexpensive and Efficient Ligand for Pd-Catalyzed Homocoupling Reactions to Synthesize Bipyridines and Their Analogues

2019 ◽  
Vol 16 (1) ◽  
pp. 173-180
Author(s):  
Mingwei Chen ◽  
Jinyu Hu ◽  
Xiaoli Tang ◽  
Qiming Zhu
Keyword(s):  
Transition Metal ◽  
Oxidation State ◽  
Coupling Reaction ◽  
Aryl Halides ◽  
Metal Species ◽  
Good Substrate ◽  
Active Metal ◽  
Homocoupling Reaction ◽  
Catalytic Cycles ◽  
Reductive Homocoupling

Aim and Objective: The synthesis of bipyridines, especially 2, 2’-bipyridines, remains challenging because the catalytic cycle can be inhibited due to coordination of bipyridine to transition metal. Thus, the development of efficient methods for the synthesis of bipyridines is highly desirable. In the present work, we presented a promising approach for preparation of bipyridines via a Pd-catalyzed reductive homocoupling reaction with simple piperazine as a ligand. Materials and Methods: Simple and inexpensive piperazine was used as a ligand for Pd-catalyzed homocoupling reaction. The combination of Pd(OAc)2 and piperazine in dimethylformamide (DMF) was observed to form an excellent catalyst and efficiently catalyzed the homocoupling of azaarenyl halides, in which DMF was used as the solvent without excess reductants although stoichiometric reductant was generally required to generate the low-oxidation-state active metal species in the catalytic cycles. </P><P> Results: In this case, good to excellent yields of bipyridines and their (hetero) aromatic analogues were obtained in the presence of 2.5 mol% of Pd(OAc)2 and 5 mol% of piperazine, using K3PO4 as a base in DMF at 140°C. Conclusion: According to the results, piperazine as an inexpensive and efficient ligand was used in the Pd(OAc)2-catalyzed homocoupling reaction of heteroaryl and aryl halides. The coupling reaction was operationally simple and displayed good substrate compatibility.

Voltammetric Studies of Some Novel Fe(III) Complexes with Quadridentate Ligands. The Axial Ligand-Exchange Reactions in DMF and DMSO

1995 ◽  
Vol 60 (7) ◽  
pp. 1140-1157 ◽  
Author(s):  
Ljiljana S. Jovanovic ◽  
Luka J. Bjelica
Keyword(s):  
Oxidation State ◽  
Chemical Reactions ◽  
Ligand Exchange ◽  
Kinetic Data ◽  
Central Atom ◽  
Axial Ligand ◽  
Exchange Reactions ◽  
Ligand Effect ◽  
Condensation Products ◽  
Voltammetric Studies

The electrochemistry of four novel Fe(III) complexes of the type [Fe(L)Cl], involving quadridentate ligands based on the condensation products of benzoylacetone-S-methylisothiosemicarbazone with salicylaldehyde, 5-chlorosalicylaldehyde, 3,5-dichlorosalicylaldehyde or 5-nitrosalicylaldehyde, was studied in DMF and DMSO at a GC electrode. All complexes undergo a two-step one-electron reductions, usually complicated by chemical reactions. In solutions containing Cl-, the ligand-exchange reactions Cl--DMF and Cl--DMSO take place. Stability of the chloride-containing complexes was discussed in terms of the coordinated ligand effect, oxidation state of the central atom and, in particular, of the donor effect of the solvent. Some relevant kinetic data were calculated.

Studies of the Synthesis of Large VAPO-5 Crystals and Incorporation of Vanadium Ions

1992 ◽  
Vol 57 (4) ◽  
pp. 767-773 ◽  
Author(s):  
Jan Kornatowski ◽  
Mikhail Sychev ◽  
Werner H. Baur ◽  
Gerd Finger
Keyword(s):  
Oxidation State ◽  
Molecular Sieve ◽  
Model Substance ◽  
Vanadium Ions

The molecular sieve VAPO-5 has been synthesized hydrothermally in form of large crystals up to 660 μm in length. They have been used as a model substance for the study of vanadium incorporation into the framework. Our results show that vanadium was incorporated into the framework though in relatively small amounts. The results are in agreement with earlier findings for powder preparations of VAPO-5, except for the oxidation state of the vanadium ions and its stability. These conclusions agree with those arrived at previously for vanadium silicate KVS-5.

Redox Potential - (Electronic) Structure Relationships in 18- and 17-Electron Mononitrile (or Monocarbonyl) Diphosphine Complexes of Re and Fe

2001 ◽  
Vol 66 (1) ◽  
pp. 139-154 ◽  
Author(s):  
M. Fátima C. Guedes Da Silva ◽  
Luísa M. D. R. S. Martins ◽  
João J. R. Fraústo Da Silva ◽  
Armando J. L. Pombeiro
Keyword(s):  
Cyclic Voltammetry ◽  
Electronic Structure ◽  
Binding Sites ◽  
Closed Shell ◽  
Carbonyl Complexes ◽  
Metal Centre ◽  
Pt Electrode ◽  
Metal Site ◽  
Oxidation Potentials ◽  
First Time

The organonitrile or carbonyl complexes cis-[ReCl(RCN)(dppe)2] (1) (R = 4-Et2NC6H4 (1a), 4-MeOC6H4 (1b), 4-MeC6H4 (1c), C6H5 (1d), 4-FC6H4 (1e), 4-ClC6H4 (1f), 4-O2NC6H4 (1g), 4-ClC6H4CH2 (1h), t-Bu (1i); dppe = Ph2PCH2CH2PPh2), or cis-[ReCl(CO)(dppe)2] (2), as well as trans-[FeBr(RCN)(depe)2]BF4 (3) (R = 4-MeOC6H4 (3a), 4-MeC6H4 (3b), C6H5 (3c), 4-FC6H4 (3d), 4-O2NC6H4 (3e), Me (3f), Et (3g), 4-MeOC6H4CH2 (3h); depe = Et2PCH2CH2PEt2), novel trans-[FeBr(CO)(depe)2]BF4 (4) and trans-[FeBr2(depe)2] (5) undergo, as revealed by cyclic voltammetry at a Pt-electrode and in aprotic non-aqueous medium, two consecutive reversible or partly reversible one-electron oxidations assigned as ReI → ReII → ReIII or FeII → FeIII → FeIV. The corresponding values of the oxidation potentials IE1/2ox and IIE1/2ox (waves I and II, respectively) correlate with the Pickett's and Lever's electrochemical ligand and metal site parameters. This allows to estimate these parameters for the various nitrile ligands, depe and binding sites (for the first time for a FeIII/IV couple). The electrochemical ligand parameter show dependence on the "electron-richness" of the metal centre. The values of IE1/2ox for the ReI complexes provide some supporting for a curved overall relationship with the sum of Lever's electrochemical ligand parameter. The Pickett parametrization for closed-shell complexes is extended now also to 17-electron complexes, i.e. with the 15-electron ReII and FeIII centres in cis-{[ReCl(dppe)2]}+ and trans-{FeBr(depe)2}2+, respectively.

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