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This category includes hydrides that exist as discrete molecules, polymers or oligomers, and hydrogen that has been chem-adsorbed to a surface. A particularly important segment of covalent hydrides are complex metal hydrides, powerful soluble hydrides commonly used in synthetic procedures.
Binary hydrogen compounds in group 1 are the ionic hydrides (also called saline hydrides) wherein hydrogen is bound electrostatically. Because hydrogen is located somewhat centrally in an electronegative sense, it is necessary for the counterion to be exceptionally electropositive for the hydride to possibly be accurately described as truly behaving ionic.
Hydrides can also span the triangular face of a cluster as in [Ag 3 {(PPh 2) 2 CH 2} 3 (μ 3-H)(μ 3-Cl)]BF 4. [5] In the cluster [Co 6 H(CO) 15] −, the hydride is "interstitial", occupying a position at the center of the Co 6 octahedron. The assignment for cluster hydrides can be challenging as illustrated by studies on Stryker's reagent [Cu ...
For hydrides other than group 1 and 2 metals, the term is quite misleading, considering the low electronegativity of hydrogen. An exception in group 2 hydrides is BeH 2, which is polymeric. In lithium aluminium hydride, the [AlH 4] − anion carries hydridic centers firmly attached to the Al(III).
In general, complex metal hydrides have the formula M x M' y H n, where M is an alkali metal cation or cation complex and M' is a metal or metalloid.Well known examples feature group 13 elements, especially boron and aluminium including sodium aluminium hydride, NaAlH 4), lithium aluminium hydride, LiAlH 4, and lithium borohydride, (LiBH 4).
Potassium hydride is produced by direct combination of the metal and hydrogen at temperatures between 200 and 350 °C: 2 K + H 2 → 2 KH. This reaction was discovered by Humphry Davy soon after his 1807 discovery of potassium, when he noted that the metal would vaporize in a current of hydrogen when heated just below its boiling point.
Sodium hydride is the chemical compound with the empirical formula Na H.This alkali metal hydride is primarily used as a strong yet combustible base in organic synthesis.NaH is a saline (salt-like) hydride, composed of Na + and H − ions, in contrast to molecular hydrides such as borane, silane, germane, ammonia, and methane.
Electrode active areas of metal hydride fuel cells have been scaled up from 60 cm 2 to 250 cm 2, enabling systems to be scaled up to 500 Watts. [11] The scaling up of electrode active areas also provided capabilities to develop higher power fuel cell stacks, each with 1500 Watts of power. [6]