Methylene-bridged, intramolecular donor–acceptor systems based on rare-earth metals and phosphinomethanides

2017 ◽  
Vol 46 (16) ◽  
pp. 5326-5336 ◽  
Author(s):  
Martin Pieper ◽  
Jan-Hendrik Lamm ◽  
Beate Neumann ◽  
Hans-Georg Stammler ◽  
Norbert W. Mitzel
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Earth Metal ◽  
Donor Acceptor ◽  
Lewis Pairs

Geminally bonded intramolecular Lewis-pairs based on rare-earth metal phosphinomethanides were prepared, characterized and tested for their reactivity towards H2, CO2and alkynes.

scholarly journals Highly efficient stabilisation of meta-ethynylpyridine polymers with amide side chains in water by coordination of rare-earth metals

2015 ◽  
Vol 13 (6) ◽  
pp. 1700-1707 ◽  
Author(s):  
Hiroki Makida ◽  
Hajime Abe ◽  
Masahiko Inouye
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Earth Metal ◽  
Helical Structure ◽  
Metal Salts ◽  
Side Chains ◽  
Highly Efficient

An amphiphilic meta-ethynylpyridine polymer with chiral amide side chains coordinated with rare-earth metal salts, especially strongly with Sc(iii), to stabilise its helical structure with CD enhancement.

scholarly journals Stability Constant of Rare Earth Metals with Substituted Thiazoles at 298.15K

2016 ◽  
Vol 64 ◽  
pp. 106-109
Author(s):  
A.B. Naik ◽  
M.S. Poharkar
Keyword(s):  
Rare Earth ◽  
Ionic Strength ◽  
Stability Constant ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Sodium Perchlorate ◽  
Earth Metal ◽  
Water Mixture ◽  
Dissociation Process ◽  
The Stability

The stability constant on complexation of rare earth metal ions Eu (III), Gd (III), Nd (III) and Tb (III) with substituted thiazole in 70% Dioxane (Dx)-water mixture have been determined by a pH and spectrophotometric method at 298.15K and ionic strength 0.1mol.dm-3(sodium perchlorate). At constant temperature, the stability constant of the formed complexes decreases in the order Tb (III), Gd (III), Eu (III), Nd (III). The dissociation process is non-spontaneous, endothermic and entrophically unfavorable while formation of metal complexes has been found to be spontaneous, endothermic and entrophically favorable.

Azopyridine-based chiral oxazolines with rare-earth metals for photoswitchable catalysis

2021 ◽  
Author(s):  
Kento Nakamura ◽  
Masaru Kondo ◽  
Chandu G Krishnan ◽  
Shinobu Takizawa ◽  
Hiroaki Sasai
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Earth Metal ◽  
Group Coordination ◽  
Azo Group ◽  
Re Catalyst

An azopyridine-based oxazoline was developed for utilizing azo group coordination and isomerization as a photoswitchable ligand. The ligand coordinated to rare-earth metal (RE) catalyst underwent efficient E/Z photoisomerization, suggesting tri-...

scholarly journals Biotechnical toxicity assessment system of rare earth metals compounds

2020 ◽  
pp. 56-67
Author(s):  
M. I. Semenova ◽  
◽  
A. V. Smirnov ◽  
A. Sokolov ◽  
A. S. Kovalevskaya ◽  
...  
Keyword(s):  
Rare Earth ◽  
Human Health ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Safety Data ◽  
Earth Metal ◽  
Toxicity Assessment ◽  
Hazardous Substances ◽  
Metal Compounds ◽  
Modern Methods

Introduction. Expanding the scope of application of rare-earth metal compounds that are unique in their properties increases the interest of many researchers in studying the impact of rare-earth metals and their compounds on human health and the environment. One of the most relevant and modern methods for assessing the safety of the studied media for a biological test object is bioassay. Problem Statement. The objective necessity of determining the combined effect of rare earth metals and their compounds on human health and the environment involves the use of biological systems. Modern methods of bioassay are extremely sensitive, which is sufficient to determine sub-threshold concentrations of hazardous substances in accordance with international standards. Thus, the use of these methods can make it possible to determine the index and the degree of toxicity of rare earth metal compounds with high accuracy in order to prepare a package of necessary documentation on industrial safety of products. Theoretical Part. Based on the studied toxicological effects of rare earth metals, the authors proposed to conduct a toxicity assessment based on the concept of biotechnical systems. The object of research was oxides and carbonates of rare earth metals. The results of the study to determine the index and the degree of toxicity of rare earth metal compounds, as well as to assess the lethal concentration of LC50 (24 h) by biotesting using test organisms Paramecium Caudatum were used to write a safety data sheet for cerium oxide and carbonate. Conclusion. The studies have shown that a certain modification of the technical solutions embedded in the devices of the Biotester series makes it possible to correctly solve the problem of assessing the toxicity of rare earth metals and their compounds. Based on the research results, the safety data sheets were developed.

Rare earth–metal bonding in molecular compounds: recent advances, challenges, and perspectives

2015 ◽  
Vol 39 (10) ◽  
pp. 7544-7558 ◽  
Author(s):  
Mikhail V. Butovskii ◽  
Rhett Kempe
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Earth Metal ◽  
Main Group ◽  
Metal Bonding ◽  
Main Group Metals ◽  
Recent Advances ◽  
Molecular Compounds

In this review, all structurally authenticated molecular compounds with direct bonds between rare earth metals and transition or main group metals are summarized. Novel aspects of their syntheses, properties and reactivities are highlighted.

Osmium and magnesium: structural segregation in the rare earth-rich intermetallics RE4OsMg (RE=La–Nd, Sm) and RE9TMg4 (RE=Gd, Tb)

2019 ◽  
Vol 74 (6) ◽  
pp. 519-525 ◽  
Author(s):  
Theresa Block ◽  
Sebastian Stein ◽  
Lukas Heletta ◽  
Rainer Pöttgen
Keyword(s):  
Rare Earth ◽  
Powder Diffraction ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Three Dimensional ◽  
Earth Metal ◽  
Intermetallic Phases ◽  
Induction Melting ◽  
X Ray ◽  
Dimensional Network

AbstractTernary rare earth metal-rich intermetallic phases containing osmium and magnesium were obtained by induction melting of the elements in sealed niobium ampoules under argon followed by annealing in muffle furnaces. The large rare earth elements form the series of Gd4RhIn-type (F4̅3m) intermetallicsRE4OsMg withRE = La–Nd and Sm, while the smaller rare earth metals gadolinium and terbium form the Y9CoMg4-type (P63/mmc) phases Gd9OsMg4and Tb9OsMg4. All samples were characterized by X-ray powder diffraction (Guinier technique). The structures of Ce4Os0.973Mg1.027(a = 1406.54(7) pm,wR2 = 0.0478), Nd4Os0.978Mg1.022(a = 1402.00(7) pm,wR2 = 0.0463), Sm4Os0.920Mg1.080(a = 1387.33(5) pm,wR2 = 0.0378) and Gd9OsMg4(a = 971.01(5),c = 980.43(5) pm,wR2 = 0.0494) were refined from single-crystal X-ray diffractometer data. The threeRE4OsMg phases show small degrees of Os/Mg mixing, as is frequently observed for Rh/In in Gd4RhIn-type intermetallics. The basic building units in both structures are osmium-centeredRE6trigonal prisms that are condensed with emptyRE6octahedra. The magnesium atoms in both types build Mg4tetrahedra. The latter are isolated (312 pm Mg–Mg in Ce4OsMg) and incorporated within the three-dimensional network of prisms and octahedra in theRE4OsMg phases while one observes rows of corner- and face-sharing tetrahedra in Gd9OsMg4(305 and 314 pm Mg–Mg). In both structure types direct Os–Mg bonding is not observed.

scholarly journals Dissolution kinetics of rare earth metal phosphates in carbonate solutions of alkali metals

2021 ◽  
Vol 251 ◽  
pp. 712-722
Author(s):  
Tatyana Litvinova ◽  
Ivan Oleynik
Keyword(s):  
Rare Earth ◽  
Calcium Carbonate ◽  
Alkali Metal ◽  
Ammonium Sulfate ◽  
Rare Earth Metal ◽  
Ammonium Carbonate ◽  
Rare Earth Metals ◽  
Earth Metal ◽  
Phosphate Dissolution ◽  
Carbonate Complexes

Treatment of apatite raw materials is associated with the formation of large-tonnage waste – phosphogypsum. The content of rare earth metals in such waste reaches 1 %, which makes it possible to consider it a technogenic source for obtaining rare earth metals and their compounds. Up to the present moment, there are neither processing plants, nor an efficient process flow to handle phosphogypsum dumps. It is rational to use a way that involves extraction of valuable components and overall reduction of phosphogypsum dumps. Such process flow is available with carbonate conversion of phosphogypsum to alkali metal or ammonium sulfate and calcium carbonate upon the condition of associated extraction of rare earth metal (REM) compounds. Associated extraction of REM compounds becomes possible since they form strong and stable complexes with hard bases according to Pearson, which among other things include carbonate, phosphate and sulfate anions. Formation of lanthanide complexes with inorganic oxygen-containing anions is facilitated by the formation of high-energy Ln-O bonds. The study focuses on the dissolution of lanthanide phosphates in carbonate media. It was established that formation of REM carbonate complexes from their phosphates is a spontaneous endothermic process and that formation of lanthanide carbonates and hydroxides serves as thermodynamic limitation of dissolution. A shift in equilibrium towards the formation of carbonate complexes is achieved by increasing the temperature to 90-100 °C and providing an excess of carbonate. The limiting stage of REM phosphate dissolution in carbonate media is external diffusion. This is indicated by increasing rate of the process with an intensification of stirring, first order of the reaction and the value of activation energy for phosphate dissolution from 27 to 60 kJ/mol. A combination of physical and chemical parameters of the process allowed to develop an engineering solution for associated REM extraction during carbonate conversion of phosphogypsum, which included a 4-5 h conversion of phosphogypsum at temperature of 90-110 °C by an alkali metal or ammonium carbonate solution with a concentration of 2-3 mol/l. As a result, a solution with alkali metal (ammonium) sulfate is obtained, which contains REMs in the form of carbonate complexes and calcium carbonate. The rate of REM extraction into the solution reaches no less than 93 %. Rare earth metals are separated from the mother liquor by precipitation or sorption on anion exchange resins, while the excess of alkali metal or ammonium carbonate is returned to the start of the process.

Reactions of Rare‐Earth Metal Based Lewis Pairs with Azides †

2020 ◽  
Vol 38 (6) ◽  
pp. 559-564 ◽  
Author(s):  
Yifan Dong ◽  
Kejian Chang ◽  
Xin Xu
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Earth Metal ◽  
Lewis Pairs

scholarly journals Study of the Solubility of Sediments of Certain Lantanoids in Carbonate Solutions

2020 ◽  
Vol 12 (4) ◽  
pp. 63-71
Author(s):  
R. Kashurin ◽  
◽  
S. Gerasev ◽  
A. Suslov
Keyword(s):  
Rare Earth ◽  
Rare Earth Metal ◽  
Rare Earth Metals ◽  
Earth Metal ◽  
Ion Concentration ◽  
Dissolution Process ◽  
Factors Affecting ◽  
Advantages And Disadvantages ◽  
Extraction Degree ◽  
Red Sludge

The study examines the dissolution process for the precipitates of the rare-earth carbonates and phosphates with a change in the concentration parameters of the system. The objective of the study is to determine the nature of the dissolution process at variable composition of the studied solutions. As a result of the theoretical base analysis, the qualitative and quantitative content of rare-earth metals in red sludge and phosphogypsum is presented, which governs the interest in this problem under consideration. The available techniques for extraction of rare-earth metals from red sludge and phosphogypsum have also been considered, their advantages and disadvantages are presented. A promising carbonate-alkali method for the extraction of rare-earth metals has been considered. Thermodynamic parameters of the system have been calculated to determine the possibility of the process. During the experiment the factors affecting the dissolution process have been examined: the carbonate ion concentration, the nature of the solvent cation and rare-earth metal cation. Carbonates and phosphates of europium, holmium, and neodymium have been considered as the analyzed components. Carbonates and phosphates of neodymium, europium, and holmium have been dissolved in model solutions of K2CO3 with the concentrations of 0.2–4.5 mol/L until reaching equilibrium. The obtained results show the dependence of solubility of the precipitates of rare-earth metals on the solvent nature and concentration. The explored data are presented as solubility isotherms. On the basis of experimental data the values of the extraction degree of a rare-earth metal into the solution have been calculated. For neodymium, europium, and holmium carbonates, the maximum recovery degree αmax is 72.8 %, 81.2 %, 83.0 %, respectively. During the experiment with dissolution of lanthanide phosphates, the following results have been obtained: the maximal degree of neodymium extraction is 60.59%, while for europium it equals 51.66 % and 93.01 % for holmium

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