The oxidation states of copper and iron in mineral sulfides, and the oxides formed on initial exposure of chalcopyrite and bornite to air

<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>

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Catalytic Fluorination of Boron Compounds at a Bismuth Redox Platform

10.26434/chemrxiv.9729143 ◽

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>

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Lower oxidation states in gallium halides

10.31274/rtd-180813-15014 ◽

1956 ◽

Author(s):

Richard K. McMullan

Keyword(s):

Oxidation States ◽

Lower Oxidation

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Evaluation of strength of concrete on different initial exposure condition

Current Materials Science ◽

10.2174/2666145413999201224112446 ◽

2020 ◽

Vol 13 ◽

Author(s):

Sri Ram Krishna Mishra ◽

Pradeep Kumar Ghosh ◽

Manoj Kulshreshtha

Keyword(s):

Portland Cement ◽

High Strength ◽

Cementitious Materials ◽

General Purpose ◽

Supplementary Cementitious Materials ◽

Exposure Condition ◽

Portland Cement Concrete ◽

Initial Exposure ◽

Skilled Manpower ◽

Standard Practices

Background: The previous studies have focused curing effect of mainly on high strength concrete, where strict supervision is maintained. This study is based upon general purpose concreting work for commercial and residential construction in absence of skilled manpower and supervision. Objective: The objective of this study is to establish a thumb rule to provide 7 days initial curing for maintaining quality for unsupervised concreting irrelevant to type of cement and grading. Methods: In this study concrete samples made with locally available commercial cements were cured for various initial exposure. Results: The results shows that concrete cured after a gap of 4 days from the time of de-moulding have given lowest strength as compared to concrete cured in standard practices i.e. where proper curing protocol had been followed. Conclusion: Initial curing is most important aspect of gaining desired strength. The findings after this study shows that curing affects the strength of concrete in variable grading. Initial curing has great importance for concrete with all types of Portland cement. Concrete with supplementary cementitious materials gives lowest strength initially but results higher strength after 28 days as compared to Portland cement.

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

10.1130/abs/2019am-336973 ◽

2019 ◽

Author(s):

M. Brounce ◽

◽

Mark K. Reagan ◽

Daniel A. Coulthard ◽

Katherine A. Kelley ◽

...

Keyword(s):

Oxidation States

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99mTc Labelling Strategies for the Development of Potential Nitroimidazolic Hypoxia Imaging Agents

Inorganics ◽

10.3390/inorganics7110128 ◽

2019 ◽

Vol 7 (11) ◽

pp. 128 ◽

Cited By ~ 3

Author(s):

Giglio ◽

Rey

Keyword(s):

Rational Design ◽

Biological Properties ◽

Fine Tuning ◽

Oxidation States ◽

Hypoxia Imaging ◽

Biological Target ◽

99Mtc Radiopharmaceuticals ◽

99Mtc Labelling

Technetium-99m has a rich coordination chemistry that offers many possibilities in terms of oxidation states and donor atom sets. Modifications in the structure of the technetium complexes could be very useful for fine tuning the physicochemical and biological properties of potential 99mTc radiopharmaceuticals. However, systematic study of the influence of the labelling strategy on the “in vitro” and “in vivo” behaviour is necessary for a rational design of radiopharmaceuticals. Herein we present a review of the influence of the Tc complexes’ molecular structure on the biodistribution and the interaction with the biological target of potential nitroimidazolic hypoxia imaging radiopharmaceuticals presented in the literature from 2010 to the present. Comparison with the gold standard [18F]Fluoromisonidazole (FMISO) is also presented.

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