Magnesium hydride

MgH2 contains 7.66% by weight of hydrogen and has been studied as a potential hydrogen-storage medium. It was discovered in 1912, during the pyrolysis of ethyl magnesium iodide (a Grignard reagent), which produced small amount of MgH2. In 1951, preparation from the elements was first reported involving direct hydrogenation of Mg metal at high pressure and temperature (200 atmospheres, 500°C)with magnesium iodide as a catalyst:
Mg＋H2→MgH2
Lower temperature production from Mg and H2 using nano-crystalline Mg produced in ball mills has been investigated. Other preparations include:
1. The hydrogenation of magnesium anthracene under mild conditions:
Mg(anthracene)＋H2→MgH2＋C14H10 2. The reaction of diethyl magnesium with LiAlH4
3. An adduct of complexed MgH2, e.g. MgH2·THF by the reaction of phenylsilane (C6H8Si) and dibutyl magnesium in ether or hydrocarbon solvents in the presence of THF (C4H8O) using TMEDA (Tetramethylethylenediamine＝(CH3)2NCH2CH2N (CH3)2) as a ligand.