Hydride compounds chemical properties

Despite the fact that many boron hydride compounds possess unique chemical and physical properties, very few of these compounds have yet undergone significant commercial exploitation. This is largely owing to the extremely high cost of most boron hydride materials, which has discouraged development of all but the most exotic appHcations. Nevertheless, considerable commercial potential is foreseen for boron hydride materials if and when economical and rehable sources become available. Only the simplest of boron hydride compounds, most notably sodium tetrahydroborate, NajBHJ, diborane(6), B2H, and some of the borane adducts, eg, amine boranes, are now produced in significant commercial quantities. 

The compound sodium hydride, formed in reaction (29), is a crystalline compound with physical properties similar to those of sodium chloride. The chemical properties are very different, however. Whereas sodium burns readily in chlorine, it reacts with hydrogen only on heating to about 300°C. While sodium chloride is a stable substance that dissolves in water to form Na+(aqJ and CV(aq), the alkali hydrides bum in air and some of them ignite spontaneously. In contact with water, a vigorous reaction occurs, releasing hydrogen ... 

In order to fully understand the electrochemical behaviour of AB, hydrides, a knowledge of their chemical properties is required. Van Vucht et al. [25] were the first to prepare LaNi5 hydride and it is arguably the most thoroughly investigated H—storage compound. It reacts rapidly with hydrogen at room temperature at a pressure of several atmospheres above the equilibrium plateau pressure. PC isotherms for this system are shown in Fig. 3. 

Pulotov, M.S. (1991) Synthesis of aluminum hydride compounds, their reactions and physical and chemical properties, Abstract of Dissertation of Doctor of Chemistry, Tashkent. 

Potassium hydride, KH.—Moissan5 prepared the hydride by a method analogous to that employed by him for the corresponding sodium derivative, the excess of potassium being dissolved by liquid ammonia. Ephraim and Michel6 passed hydrogen into potassium at 350° C., and found the reaction to be promoted by the presence of calcium. The hydride forms white crystals of density 0-80. The vapour-tension for each temperature-interval of 10° between 350° and 410° C. corresponds with the values 56, 83, 120, 168, 228, 308, and 430 mm. respectively.7 In chemical properties potassium hydride resembles the sodium compound, but is less stable. Its stability is greater than that of rubidium hydride or caesium hydride. Carbon dioxide converts it into potassium formate. 

In this chapter, we shall first briefly survey the methods used for the synthesis or generation of paramagnetic hydride complexes, subsequently survey the known classes of stable open-shell hydride complexes, then review our current knowledge on the fundamental properties of the M-H bond in open-shell compounds, and finally examine the various established decomposition modes. No review articles specifically focusing on paramagnetic hydride compounds and their chemical reactivity appear to have been previously published. With few exceptions, this chapter will be limited to the analysis of monometallic species of the d elements. The f elements are treated in a separate chapter in this... 

There seems to be some confusion about the polarization of the metal-hydrogen bond in certain hydrido-transition metal-carbonyl compounds, in particular HCo(CO)4. This and some related hydrido-carbonyl compounds are slightly soluble in water, and such solutions are clearly acidic In the gas phase or in non-polar solvents, however, these complexes exhibit spectroscopic and chemical properties similar to those of other non-acidic hydride complexes. A MO calculation of the charge densities in HCo(CO)4 indicated that 1.6 electrons are associated with the hydrogen atom, and the question was discussed as to how a molecule with a negative-... 

---