Strontium and Barium Hydrides

OtherAlkaline-Parth Hydrides. Strontium and barium hydrides resemble calcium hydride in properties and reactivity. They have no significant commercial apphcations. 

Another salt-like group of compounds that have acid-base properties is the hydrides of the alkali metals and calcium, strontium, and barium. These hydrides will react with water to form the hydroxide ion and hydrogen gas ... 

Magnesium, strontium, and barium form similar compounds. Beryllium hydride cannot be formed by direct combination of the elements but can be prepared by the following reaction ... 

In contrast, magnesium requires dilute acids in order to react (to the salt plus hydrogen), and beryllium is resistant to acid attack. A similar trend is seen in the direct reaction of hydrogen under mild conditions calcium, strontium, and barium give ionic hydrides, high pressures are required to form magnesium hydride, and beryllium hydride can not be prepared by direct combination. 

Perchlorates are powerful oxidizing substances. These compounds explode when mixed with combustible, organic, or other easily oxidizable compounds and subjected to heat or friction. Perchlorates explode violently at ambient temperatures when mixed with mineral acids, finely divided metals, phosphorus, trimethylphosphite, ammonia, or ethylenediamine. Explosions may occur when perchlorates are mixed with sulfur, or hydride of calcium, strontium, or barium and are subjected to impact or ground in a mortar. Perchlorates react with fluorine to form fluorine perchlorate, an unstable gas that explodes spontaneously. Heating perchlorates to about 200°C (392°F) with charcoal or hydrocarbons can produce violent explosions. Metal perchlorates from complexes with many organic solvents, which include benzene, toluene, xylenes, aniline, diozane, pyridine, and acetonitrile. These complexes are unstable and explode when dry. Many metal perchlorates explode spontaneously when recrystaUized from ethanol. Saturated solution of lead perchlorate in mathanol is shock sensitive. 

Mhere materials are labelled with an asterisk, a large number of powders were successfully deposited using the suspension medium described. Mizuguchi et al included alumina barium, strontium and calcium carbonates magnesia, zinc oxide, titanium dioxide, silica, indium oxide, lanthanum boride, tungsten carbide, cadmium sulfide and several metals and phosphors. The list of materials described by Gutierrez et al included several metals carbides of molybdenum, zirconium, tungsten, thorium, uranium, neptunium and plutonium zirconium hydride, tantalum oxide and uranium dioxide. In addition, many metallic and oxide powder suspensions in alcohols, acetone and dinitromethane were studied by Brown and Salt ... 

Mixtures with calcium hydride or strontium hydride may explode readily, and interaction of the molten chlorate is, of course, violent. A mixture of syrupy sodium phosphinate ( hypophosphite ) and the powdered chlorate on heating eventually explodes as powerfully as glyceryl nitrate. Calcium phosphinate mixed with the chlorate and quartz detonates (the latter producing friction to initiate the mixture). Dried mixtures of barium phosphinate and the chlorate are very sensitive and highly explosive under the lightest confinement (screwed up in paper). 

Lithium, calcium, barium and strontium react readily, sometimes igniting, in hydrogen above 300°C, while sodium and potassium react more slowly to form the hydrides. 

Syntheses that exploit the solubility of the alkaline-earth metals in liquid ammonia have proven practical for alkoxide work, as they generate high yields, reaction rates, and purity (Table 8, Equation (3)). In a refinement of this approach, Caulton and co-workers have used dissolved ammonia in an ethereal solvent, usually THF, to effect the production of a number of alkoxides of barium, and this method has also been examined with calcium and strontium (Table 8, Equations (4a) to (4c)). Displacement reactions using alkali metal alkoxides and alkaline-earth dihalides (Table 8, Equation (5)), and between alkaline-earth hydrides or amides and alcohols (Table 8, Equations (6) and (7)), have been examined, but alkali-metal halide impurities, incomplete reactions, and unexpected equilibria and byproducts can affect the usefulness of these approaches. 

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