Arsinide

Not to be confused with Arsenide.

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 AsH−2. It can be considered as a ligand with name arsenido or arsanido. Few chemists study arsanyl compounds, as they are both toxic and unstable.^[1] The IUPAC names are arsanide and dihydridoarsenate(1−). For the ligand the name is arsanido. The neutral −AsH₂ group is termed arsanyl.

Arsinide

Names
IUPAC name Arsanide
Other names Arsinide Dihydridoarsenate(1−) Dihydridoarsenate(III) Dihydrogen arsenate(III)
Identifiers
CAS Number	13937-35-4 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:29755
ChemSpider	19232526
Gmelin Reference	217243
InChI InChI=1S/AsH2/h1H2/q-1 Key: DRQOYSLXOZXEBV-UHFFFAOYSA-N
SMILES [AsH2-]
Properties
Chemical formula	AsH2−
Molar mass	76.938 g·mol−1
Related compounds
Related compounds	Arsanylium AsH+2 Arsine AsH3 Azanide NH−2 Phosphanide PH−2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

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.^[2]

Arsinides are also formed when arsine reacts with thin layers of alkali metals.^[3]

The arsine may reduce some compounds to metals, so for example an attempt to make an indium arsinide results in metallic indium.^[1]

Reactions

When heated, metal hydrogen arsinide and metal dihydrogen arsinide compounds lose hydrogen to become a metal arsenide:

NaAsH₂ → NaAs + H₂^[3]

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

2 LiAsH₂ → Li₂AsH + AsH₃^[3]

These reactions take place even at room temperature, and result in a discolouration of the original chemical.^[3]

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.^[4]

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.^[5]

Arsinides react with water to yield arsine AsH₃:

KAsH₂ + H₂O → KOH + AsH₃^[6]

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−As(C₆H₅)₂ and triphenylarsine As(C₆H₅)₃.^[7]

Potassium dihydrogen arsinide KAsH₂ reacts with a silyl halide, e.g. chlorosilane SiH₃Cl, producing trisilylarsine.^[8]

Potassium dihydrogen arsinide KAsH₂ reacts with H₂As−BH₂·N(CH₃)₃ and a crown ether resulting in [K(C₁₂H₂₄O₆)]⁺[H₂As−BH₂−AsH₂]⁻.^[9]

List

Formula	Name	Crystal system	Space group	Unit cell (Å)	Volume	Density	Comment	ref
LiAsH2	Lithium arsanide							[3]
Li2AsH	Dilithium arsanide						decomposition at 0°C	[3]
LiAsH2·2NH3								[3]
LiAsH2·4NH3								[3]
NaAsH2	Sodium arsanide						white; decomposition at room temperature	[2]
Na2AsH	Disodium arsanide							[3]
NaAsH2·2NH3								[3]
NaAsH2·4NH3								[3]
Li+[Al(AsH2)4]−	Lithium tetraarsanidoaluminate							[1]
(Dipp2Nacnac)Al(AsH2)2 Dipp2Nacnac=HC[C(Me)N(2,6-iPr2C6H3)]2								[1]
IDipp⋅AlH2AsH2 IDipp=1,3-bis(2,6-diisopropylphenyl)imidazolin-2-ylidene)		monoclinic	I2/a				colourless	[10]
IDipp⋅AlH(AsH2)2		monoclinic	I2/a	a 18.3591 b 9.0485 c 34.4864 β 91.580°				[10]
KAsH2	Potassium arsanide						stable to 80°C; decomposition at 90°C	[2]
Ca(AsH2)2	Calcium arsanide							[2]
(Dipp2Nacnac)Ga(AsH2)2								[1]
IDipp⋅GaH2AsH2		monoclinic	I2/a				colourless	[10]
IDipp⋅GaH(AsH2)2		monoclinic	I2/a	a 18.465 b 9.1493 c 34.661 β 91.509°				[10]
Th(TrenTRIPS)AsH2							Th-As 3.065 Å	[11]
U(TrenTRIPS)AsH2							U-As 3.004 Å	[11]

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 −CH₃, like in potassium methyl arsinide (K⁺CH₃AsH⁻),^[12] or by trimethylsilyl −Si(CH₃)₃.^[1] The doubly bonded ligand =AsH (or AsH²⁻) is called arsinidene.^[11]