| Description | 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. |
| Chemical Properties | Light grey powder |
| Chemical Properties | Magnesium hydride is a coarse, gray crystalline solid. |
| General Description | Magnesium hydride is a white crystalline solid. Magnesium hydride reacts violently with water and may ignite upon contact with air. Magnesium hydride is used to make other chemicals. |
| Air & Water Reactions | Highly flammable. Pyrophoric, ignites spontaneously in air and forms magnesium oxide and water [Merck 11th ed. 1989]. Reacts with water to form caustic solution of magnesium hydroxide and hydrogen gas (H2) and heat sufficient to ignite the evolved hydrogen [Merck 11th ed. 1989]. |
| Reactivity Profile | Hydrides, such as Magnesium hydride, are reducing agents and react rapidly and dangerously with oxygen and with other oxidizing agents, even weak ones. Thus, they are likely to ignite on contact with alcohols. Hydrides are incompatible with acids, alcohols, amines, and aldehydes. |
| Health Hazard | Inhalation or contact with vapors, substance or decomposition products may cause severe injury or death. May produce corrosive solutions on contact with water. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution. |
| Fire Hazard | Produce flammable gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Runoff may create fire or explosion hazard. |
| Potential Exposure | Used in hydrogen production and in
production of magnesium alcoholates. |
| Shipping | UN2010 Magnesium hydride, Hazard Class: 4.3;
Labels: 4.3-Dangerous when wet material. |
| Incompatibilities | A strong reducing agent. Pyrophoric:
the powder or dust may ignite spontaneously in air, or
in the presence of moisture. Contact with water or steam
forms magnesium hydroxide, flammable hydrogen gas,
and enough heat to ignite the hydrogen. Violent reaction
with oxidizers, alcohols, halogens, chlorinated solvents.
Incompatible with strong acids, acid chlorides, alcohols,
amines and aldehydes. Store under nitrogen. Decomposes
@ 280C in high vacuum |
