Alkaline-Earth Metal Hydrides

Alkaline-Earth Metal Hydrides. Table 2 gives thermochemical data of alkaline-earth metal hydrides. AH form orthorhombic crystals. 

Table 2. Physical Properties of Alkaline-Earth Metal Hydrides...

Reactions with alkali and alkaline earth metal hydrides also produce the same ionic metallic hydrazides ... 

A 1.84 g sample of an alkaline earth metal hydride was treated with an excess of dilute hydrochloric acid, and the resulting gas was collected in a 1.000 L container at 20°C. The measured pressure of the gas was 750.0 mm Hg. Identify the alkaline earth metal, and write the formula for the metal hydride. 

SAFETY PROFILE Poison by ingestion and intraperitoneal routes. A trace mineral added to animal feeds. Potentially explosive reaction with charcoal + ozone, metals (e.g., powdered aluminum, copper), arsenic carbon, phosphoms, sulfur, alkali metal hydrides, alkaline earth metal hydrides, antimony sulfide, arsenic sulfide, copper sulfide, tin sulfide, metal cyanides, metal thiocyanates, manganese dioxide, phosphorus. Violent reaction with organic matter. When heated to decomposition it emits very toxic fumes of I and K2O. See also lODATES. 

Alkali or alkaline-earth metal hydride reductions of P compounds are less effective than those using complex hydrides, e.g., LiAlH . Phosphorus tribromide reacts with LiH in Et,0 at O C to form a phosphorus subhydride quantitatively ... 

Formation of Bonds between Hydrogen and Group IA or IIA Metals 157 1.8.3. Alkaline-Earth Metal Hydrides... 

The state of the art of reductions with metal hydrides a decade ago was the subject of comprehensive reviews. A detailed survey of reductions of carbonyl compounds with alkali and alkaline earth metal hydrides, borane and derivatives, alane and derivatives, metal borohydrides, metal aluminohydrides, silanes, stannanes and transition metal hydrides was compiled. The properties, preparation and applications of each reagent were discussed together with methods for their determination, handling techniques... 

The importance of lithium hydride in the production of simple and complex hydrides is dependent upon certain unique properties. For example, according to Hurd (19 )y it is the very slight solubility of lithium hydride in polar organic compounds as well as the ability to sustain metathetical reactions that provides for the production of numerous hydrides. This is true for lithium hydride, whereas the other alkali and alkaline earth metal hydrides are insoluble in polar organic solvents, and their metathetical reactions do not proceed at all or at a slow rate at best (19,29). Greater use of lithium hydride is possible in such reactions because of its low dissociation pressure at its melting point of 680 °C. 

Chemical Hydrides. Primary hydride systems of various types are being developed for use in small fuel cell systems. These are irreversible (throw-away) chemical systems that generate hydrogen on demand. The active reactant is generally an alk i or alkaline earth metal hydride (sometimes in complex form). This typically is caused to react with water to form hydrogen and a metal oxide (or mixed metal oxide). Analogous chemical hydride systems are also being explored. 

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