Hydrides acid-base properties

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 ... 

The mechanistic subtypes presented throughout this book include those related to the acid-base properties of organic molecules. These are protonations, deprotonations, and proton transfers. Mechanistic types based on solvation effects include solvolysis reactions, SN1, and El processes. Additional mechanisms utilizing ionic interactions include SN2, SN2, E2, 1,2-additions, 1,4-additions, and addition-elimination processes. Finally, those mechanistic types dependent upon the presence of cationic species include alkyl shifts and hydride shifts. 

The majority of homoleptic carbonyls and many other derivatives can be formed with PF3 hgands instead of CO. In many instances, CO is exchanged by PF3 under pressure. In contrast to the elusive nature of (3), its PF3 analog HCo(PF3)4 is of very high thermal stability and does not decompose below 250 °C. Its acid base properties seem to resemble those of the carbonyl hydride, however. 

All such acids may also be given structure-based systematic names using principles already described in preceding chapters on substitutive and additive nomenclature, so in that respect the acid -containing names are superfluous. Furthermore, many species which would be classified as acids based on their chemical properties are never named as such, e.g. aqua ions such as hexaaquaaluminium(3+), and hydrides and derivatives such as ammonium, hydrogen sulfide (sulfane), etc. The term acid is thus not used consistently. 

Transition metal hydrides, which are weakly basic as isolated molecules, are expected to display acidic properties in solution. With an appropriate choice of solvent we are thus able to induce Umpolung of the acid-base behavior of certain transition metal hydrides. The break-even point of a TMH in water would be reached with 3.7. This relatively low value indicates that most transition metal hydrides will dissociate protons in water. 

It is known that transition metal hydrides exhibit acidic properties and it has been reported that in some cases complexes containing a group IV metal ligand react with weak bases ... 

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