Non-cyclopentadienyl organometallic compounds of calcium, strontium and barium

The use of sterically demanding ligands has allowed the organometallic compounds of the heavy alkaline-earth metals calcium, strontium and barium to emerge from the shadow cast by the far better studied organomagnesium Grignard reagents. Metallocenes and other cyclopentadienyl-based complexes have been the most intensively investigated, but in the past decade a wealth of new non-cyclopentadienyl compounds have been characterized. A broad range of structure types are known, encompassing σ- and π-bound anionic ligands, and Lewis base adducts with neutral donors. In this review, crystallographically characterized complexes are discussed, and current interpretations of the bonding in heavier Group 2 element compounds are examined. Recent applications of non-cyclopentadienyl compounds in organic synthesis are surveyed.     

Rhodizonate as reagent for barium,strontium, and calcium

Summary The specificity and sensitivity of the spot tests for barium and strontium is improved by treating the brownish red rhodizonate fleck with a solution of dimethylamine hydrochloride. Calcium may be identified by the separation of characteristic crystals after adding a solution of rhodizonic and benzoic acids. A simple scheme of separation has been developed, which makes use of these confirmatory tests.

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Zusammenfassung Die Spezifität und Empfindlichkeit der Tüpfelproben für Barium und Strontium wird durch Behandlung des mit Natriumrhodizonat erhaltenen Tüpfelfleckes mit Dimethylaminhydrochlorid verbessert. Calcium kann durch die Abscheidung von charakteristischen Kristallen nachgewiesen werden, die nach Zugabe einer Lösung von Rhodizonsäure und Benzoesäure erhalten werden. Ein einfacher Trennungsgang wurde ausgearbeitet, der die nutzbringende Verwendung dieser Nachweisproben möglich macht.

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Résumé La spécificité et la sensibilité de la recherche du baryum et du strontium par essais à la touche sont améliorées en traitant la tache rouge brunâtre de rhodizonate par une solution de chlorhydrate de diméthylamine. Le calcium peut être identifié par la séparation de cristaux caractéristiques après addition d'une solution d'acides rhodizonique et benzoïque. On a mis au point un schéma simple de séparation dans lequel on fait usage de ces tests de confirmation.

     

Densities of liquid metals: calcium,strontium, barium

Abstract

We report a method of measuring the densities of liquids at intermediate temperatures which employs Archimedes' Principle in a two-sinker arrangement. This method is then used to measure the densities of pure liquid calcium, strontium, and barium. We find ρ(Ca) = 1.4931 ? 1.37 × 10^?4 T(°C) from 850 ? 950°C, ρ(Sr) = 2.5547 ? 2.83 × 10^?4 T(°C) from 780 ? 880°C, and ρ(Ba) = 3.5561 ? 2.99 × 10^?4 T(°C) from 730 ? 830°C, where the units are gm/cm³. We use relations critical constants for these liquids to estimated dρ/dT, and compare these values of dρ/dT with those for other liquid metals; we also compare our results with recent x-ray diffraction data for these liquid metals.     

Microdetermination of calcium, strontium and barium using the ring-oven method

Summary The ring-oven technique is recommended for the identification and determination of Ca, Sr and Ba in the micro scale. The elements are first converted into their nitrates and Ca is washed out by a mixture of absolute alcohol and ether. Sr is then separated from Ba as soluble diethyldithiocarbamidate in alcohol-ether. The rings obtained are developed by rhodizonate (Sr, Ba) and pyrogallol (Ca). Quantitative determinations are possible by comparison with standard rings. 0.60 g of Ca, 1.31 g of Sr and 8.24 g of Ba can be determined with an error lower than 6%.

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Zusammenfassung Zur Trennung und Bestimmung von Ca, Sr und Ba im Mikromaßstab wird die Ringofen-Technik empfohlen. Die drei Elemente werden dabei zunächst in die Nitrate übergeführt und Ca mit Äther-Alkohol ausgewaschen. Sr und Ba werden anschließend mit Diäthyldithiocarbamidat behandelt und Sr mit Äther-Alkohol abgetrennt. Die Identifizierung erfolgt mit Pyrogallol (Ca) bzw. Rhodizonat (Sr, Ba). Durch Vergleich mit Standardproben ist eine quantitative Bestimmung möglich. Hierbei können noch 0,60 g Ca, 1,31 g Sr und 8,24 g Ba mit einem Fehler < 6% erfaßt werden.

     

A structural study of calcium,strontium and barium crown ether complexes

Complexes involving the perchlorate, chloride, bromide or iodide salts of the heavy group 2 elements, calcium, strontium or barium, and either 15-crown-5 or 18-crown-6 have been synthesized and their X-ray crystal structures determined. A variety of coordination modes are presented between the crown ether and metal ions.     

Study of hydrogen isotope exchange on calcium, strontium and barium hydrides

The isotope exchange of hydrogen on rare-earth metal hydrydes has been studied. When passing from Ca to Sr and Ba, the activation energy decreases and, correspondingly, the rate of exchange increases. A similar dependence is observed for the isotope exchange of oxygen on the corresponding oxides and of nitrogen on nitrides.

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. Ca Sr Ba . .

     

Synthesis of calcium, strontium, and barium fluorides by thermal decomposition of trifluoroacetates

Alkaline-metal (barium, strontium, and calcium) fluorides with a highly developed specific surface are synthesized by the thermal decomposition of the corresponding metal trifluoroacetates in an inert atmosphere followed by annealing in an oxygen flow at 500°C. The specific surfaces of the synthesized samples are studied by comparative nitrogen adsorption. The resulting specific surface values are 43.67, 36.52, and 23.98 m²/g for CaF₂, SrF₂, and BaF₂, respectively.     

Microwave synthesis of barium titanate,strontium zirconate,and sodium indium tungstate

The results of microwave (at a frequency of 2.45 GHz) synthesis of BaTiO₃, SrZrO₃, and NaIn(WO₄)₂ are compared with those of the common solid-phase synthesis.     

Scheme for the systematic identification of barium,strontium and calcium in mixtures

Summary A scheme of separation has been devised and tested, which permits detecting 1 g of any one of the common alkaline earth metals in presence of 250 g of the others. On the milligram scale, the precipitation and analysis of the group requires from 40 to 75 minutes.

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Zusammenfassung Ein Trennungsgang, der den Nachweis von 1 g jedes der üblichen Erdalkalien in Gegenwart von 250 g der anderen gestattet, wurde ausgearbeitet und geprüft. Im Milligramm-Maßstab genügen 40 bis 75 Minuten für Fällung und Analyse der Gruppe. Auf Grund einer Vorprüfung wird der Trennungsgang der Zusammensetzung der Probe angepaßt. Große Mengen von Barium werden als Nitrat in Aceton abgeschieden; Calciumnitrat wird mit Methyläthylketon extrahiert.

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Résumé On a élaboré et mis à l'épreuve un plan de séparation qui permet de déceler 1 à 2g de chacun des métaux alcalino-terreux connus, en présence de 250g des autres. A l'échelle du milligramme, la précipitation et l'analyse du groupe demande 40 à 75 minutes.

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Presented before the Congreso Panamericana de Farmacía y Bioquímica, Santiago, Chile, 1960.     

High temperature synthesis of some strontium and barium 2,6-dibenzylphenolates

Direct treatment of HOdbp (= 2,6-dibenzylphenol) with strontium or barium metal in the absence of solvent at high temperature provides the corresponding phenolates Sr(Odbp)₂ and Ba(Odbp)₂. Recrystallisation of Ba(Odbp)₂ from THF gave a good yield of the crystalline dimer [Ba(Odbp)₂(THF)]₂ · 2THF. Attempted recrystallisation of Sr(Odbp)₂ from THF mostly yielded microcrystalline material characterized as [Sr(Odbp)₂]_n but on one occasion gave a small crop of crystalline [Sr₉(Odbp)₈(O₂SiMe₂)₄(OH)₂(THF)₆(OH₂)₂] · 6THF derived from the adventitious reaction of Sr(Odbp)₂ with dimethylsilicone grease ({OSiMe₂}_∞). In the solid-state [Ba(Odbp)₂(THF)]₂ · 2THF displays significant intramolecular Ba?π-arene interactions with the pendant benzyl substituents. [Sr₉(Odbp)₈(O₂SiMe₂)₄(OH)₂(THF)₆(OH₂)₂] · 6THF features a square prismatic [Sr(O₂SiMe₂)₄]⁶⁻ core capped by two inverse crown-like square [Sr₄(Odbp)₄(OH)(L)₄]³⁺ units, where L = OH₂ or THF, that are staggered with respect to the cuboidal core.     

Lanthanum chromites partially substituted by calcium,strontium and barium synthesized by urea combustion

Because of their electrical, magnetic and catalytic properties rare earth and transition metal mixed oxides are important compounds. Lanthanum chromites have been extensively used as solid oxide fuel cell (SOFC) interconnect materials. In this work, lanthanum chromites partially substituted by alkaline earth metals were synthesized by the urea combustion process. TG and DSC techniques were used to evaluate the presence of the organic material in the powder after reaction on the hot plate. The powders were calcinated at 900°C and characterized by XRD and SEM. The results show that the particles have nanometric dimensions and the perovskite structure was formed.     

Raman spectroscopic studies of temperature dependent anomalies of strontium,barium, lead,and calcium nitrate

Raman studies of normal and ¹⁸O-substituted Sr(NO₃)₂ have been performed over a range of temperatures (77 to 580°K) to investigate the anomalous component previously observed in the symmetric stretching region. The results suggest that the peak may have a hot band origin. Impurity ions, N ¹⁸O ¹⁶O^?₂ and vibrationally excited 1NO^?₃ ions, give rise to local modes (deep-well impurity centers) in the ν₁ and ν₄ (N ¹⁸O ¹⁶O^?₂ only) regions but delocalized modes (shallow-well impurity centers) in the other internal and external mode regions. The host lattice was able to tolerate a large fraction of this type of impurity without interference with the dynamical coupling. Anomalous properties previously reported appear to be due to freezing out of the hot band. A less complete study of Ca(NO₃)₂, Ba(NO₃)₂ at room temperature and at temperature near 500°K suggests behavior similar to Sr(NO₃)₂.     

The chromatographic separation of a mixture of the chlorides of calcium,strontium, barium and magnesium

The chlorides of calcium, strontium, bitnum and magnesium have been separated on circular paper, using mixed alcohols, containing mcthanol as one of the constituents, as solvents. Approximate R_F values obtained by using ethanol containing 50%, methanol, have been reported     

Determination of calcium,strontium and barium in single crystals of alkali halides by neutron activation

The determination by neutron activation of trace quantities of calcium, strontium and barium in single crystals of alkali halides has been studied. The matrix is eliminated before the irradiation by an ion-exchange procedure. Gamma spectroscopy after radiochemical separation is used to determine strontium and barium. Calcium is determined by measuring the β-activity of ⁴⁹Sc formed by the decay of ⁴⁹Ca. Long-lived radioactive tracers are used to determine the chemical yields.     

Nuclear magnetic resonance and X-ray evidence of crystal structure for acetates of calcium,strontium, and barium

High-resolution ¹³C spectra of calcium acetate hemihydrate (CAH), strontium acetate hemihydrate (SAH), and barium acetate monohydrate (BAM) have been obtained using cross-polarization (CP), high-power decoupling, and magic-angle spinning (MAS). The results indicate the existence in each case of four nonequivalent crystallographic sites for the acetate groups. These findings have been confirmed for SAH and BAM by single-crystal X-ray diffraction studies. The carboxyl chemical shifts for CAH cover a range of 9.3 ppm and the lines are remarkably sharp, so that this material is suggested as a suitable standard for checking the performance of CP/MAS spectrometers     

Study of the thermal behaviour of copolymers of styrene with magnesium,calcium, strontium and barium acrylates

The processes of thermal destruction of copolymers of styrene with magnesium, calcium, strontium and barium acrylates have been investigated by TG and the temperature characteristics have been determined. Though the thermal stability of the metal acrylates exceeds markedly that of polystyrene, the introduction of low concentrations of the salts caused an observable deterioration of the thermal resistance of the copolymers. This was in agreement with the calculated values of the kinetic parameters of decomposition for the samples studied.

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Zusammenfassung Mittels TG wurde der thermische Abbauvorgang von Kopolymeren aus Styrol und Magnesium-, Calcium-, Strontium- und Bariumacrylaten untersucht und eine Temperaturcharakteristik erstellt. Obwohl die thermische Stabilität der Metallacrylate die von Polystyrol eindeutig übertrifft, führt die Einführung dieser Salze in geringer Konzentration zu einer merklichen Verschlechterung der Hitzebeständigkeit der Kopolymere. Diese Feststellung stimmt mit den für die Zersetzung der untersuchten Proben berechneten kinetischen Parametern überein.

     

Direct large-scale synthesis of perovskite barium strontium titanate nano-particles from solutions

This paper reports a wet chemical synthesis technique for large-scale fabrication of perovskite barium strontium titanate nano-particles near room temperature and under ambient pressure. The process employs titanium alkoxide and alkali earth hydroxides as starting materials and involves very simple operation steps. Particle size and crystallinity of the particles are controllable by changing the processing parameters. Observations by X-ray diffraction, scanning electron microscopy and transmission electron microscopy TEM indicate that the particles are well-crystallized, chemically stoichiometric and ∼50 nm in diameter. The nanoparticles can be sintered into ceramics at 1150 °C and show typical ferroelectric hysteresis loops.