Arsinide

An arsinide, arsanide, dihydridoarsenate(1−) or arsanyl compound is a chemical derivative of arsine, where one hydrogen atom is replaced with a metal or cation. The arsinide ion has formula AsH2−. It can be considered as a ligand with name arsenido or arsanido. Few chemists study arsanyl compounds, as they are both toxic and unstable. The IUPAC names are arsanide and dihydridoarsenate(1−). For the ligand the name is arsanido. The neutral \sAsH2 group is termed arsanyl.

Formation
Alkali metal arsinides can form by bubbling arsine through a liquid ammonia solution of alkali metal such as sodium, potassium or alkaline earth metal such as calcium.

Arsinides are also formed when arsine reacts with thin layers of alkali metals.

The arsine may reduce some compounds to metals, so for example an attempt to make an indium arsinide results in metallic indium.

Reactions
When heated, metal hydrogen arsinide and metal dihydrogen arsinide compounds lose hydrogen to become a metal arsenide:
 * NaAsH2 → NaAs + H2

With lithium dihydrogen arsinide LiAsH2, it can also lose arsine AsH3 to become dilithium hydrogen arsinide Li2AsH:
 * 2 LiAsH2 → Li2AsH + AsH3

These reactions take place even at room temperature, and result in a discolouration of the original chemical.

Sodium dihydrogen arsinide NaAsH2 reacts with alkyl halides RX (where X = F, Cl, Br, I, and R is alkyl) to make dialkylarsine AsHR2. Potassium dihydrogen arsinide KAsH2 reacts with alkyl halides to make trialkylarsine AsR3.

Sodium dihydrogen arsinide NaAsH2 reacts with diethyl carbonate (CH3CH2O)2CO to yield the 2-arsaethynolate [OCAs]− ion, (analogous with cyanate [OCN]− ion) which can be crystallised with the sodium ion Na+ and 18-crown-6.

Arsinides react with water to yield arsine AsH3:
 * KAsH2 + H2O → KOH + AsH3

Potassium dihydrogen arsinide KAsH2 reacts with halobenzenes C6H5X, where X = Cl, Br, I (chlorobenzene C6H5Cl, bromobenzene C6H5Br, iodobenzene C6H5I) to produce benzene C6H6, tetraphenyldiarsine (C6H5)2As\sAs(C6H5)2 and triphenylarsine As(C6H5)3.

Potassium dihydrogen arsinide KAsH2 reacts with a silyl halide, e.g. chlorosilane SiH3Cl, producing trisilylarsine.

Potassium dihydrogen arsinide KAsH2 reacts with H2As\sBH2*N(CH3)3 and a crown ether resulting in [K(C12H24O6)]+[H2As\sBH2\sAsH2]−.

Related
The hydrogen atoms in the arsinide anion may be substituted by organic or other groups which can then also produce ions, for example by methyl \sCH3, like in potassium methyl arsinide (K+CH3AsH−), or by trimethylsilyl \sSi(CH3)3. The doubly bonded ligand =AsH (or AsH(2−)) is called arsinidene.