Английская Википедия:Inorganic imide

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The inorganic imides are compounds containing an ion composed of nitrogen bonded to hydrogen with formula HN²⁻. Organic imides have the NH group, and two single or one double covalent bond to other atoms. The imides are related to the inorganic amides (H₂N⁻), the nitrides (N³⁻) and the nitridohydrides (N³⁻•H⁻).

In addition to solid state imides, molecular imides are also known in dilute gases, where their spectrum can be studied.

When covalently bound to a metal, an imide ligand produces a transition metal imido complex.

When the hydrogen of the imide group is substituted by an organic group, an organoimide results. Complexes of actinide and rare earth elements with organoimides are known.

Properties

Lithium imide undergoes a phase transition at 87 °C where it goes from an ordered to a more symmetric disordered state.

Structure

Many imides have a cubic rock salt structure, with the metal and nitrogen occupying the main positions. The position of the hydrogen atom is hard to determine, but is disordered.

Many of the heavy metal simple imide molecules are linear. This is due to the filled 2p orbital of nitrogen donating electrons to an empty d orbital on the metal.

Formation

Heating lithium amide with lithium hydride yields lithium imide and hydrogen gas. This reaction takes place as released ammonia reacts with lithium hydride.

Heating magnesium amide to about 400 °C yields magnesium imide with the loss of ammonia. Magnesium imide itself decomposes if heated between 455 and 490 °C.

Beryllium imide forms from beryllium amide when heated to 230 °C in a vacuum.

When strontium metal is heated with ammonia at 750 °C, the dark yellow strontium imide forms.

When barium vapour is heated with ammonia in an electrical discharge, the gaseous, molecular BaNH is formed. Molecules ScNH, YNH, and LaNH are also known.

Hydrogen storage

Inorganic imides are of interest because they can reversibly store hydrogen, which may be important for the hydrogen economy. For example, calcium imide can store 2.1% mass of hydrogen. Li₂Ca(NH)₂ reversibly stores hydrogen and release it at temperatures between 140 and 206 °C. It can reversibly hold 2.3% hydrogen. When hydrogen is added to the imide, amides and hydrides are produced. When imides are heated, they can yield hydridonitrides or nitrides, but these may not easily reabsorb hydrogen.

List

Ionic

name	formula	structure	space group	unit cell	references
Lithium imide	Li2NH	cubic	FmШаблон:Overbarm	a=5.0742
Beryllium imide	BeNH
Magnesium imide	MgNH	hexagonal	P6/m	a = 11.567 Å c = 3.683Å Z=12
Lithium magnesium imide	Li2Mg(NH)2
	Si2N2(NH)
	K2Si(NH)3	amourphous
	K2Si2(NH)5	amourphous
	K2Si3(NH)7	amourphous
potassium imido nitrido silicate	K3Si6N5(NH)6	cubic	P4332	a = 10.789
Calcium imide	CaNH	hexagonal	Fm3m
Lithium calcium imide	Li2Ca(NH)2	hexagonal
Magnesium calcium diimide	MgCa(NH)2	cubic
Lithium calcium magnesium imide	Li4CaMg(NH)4
Strontium imide	SrNH	orthorhombic	Pmna	a =7.5770 b =3.92260 c =5.69652 Z=4
Tin amide imide	Sn(NH2)2NH
Barium imide	BaNH	tetragonal	I4/mmm	a=4.062 c=6.072 Z=2
Lanthanum imide	La2(NH)3	rock salt		a=5.32
Cerium imide	CeNH
Ytterbium imide	YbNH	cubic		a=4.85
	NH4[Hg3(NH)2](NO3)3	cubic	P4132	a = 10.304, Z = 4
Thorium nitride imide	Th2N2(NH)	hexagonal	P3mШаблон:Overbar	a = 3.886 c = 6.185 Å

Molecular

name	formula	structure	symmetry	CAS	references
	B2(NH)3	polymer
Nitroxyl	HNO	bent		14332-28-6
	Al(NH2)(NH)	polymer
silicon dimide	Si(NH)2
thionitrosyl hydride	HNS	bent		14616-59-2
sulfur diimide	S(NH)2
Heptasulfur imide	S7NH			293-42-5
1,2,3,4,5,7,6,8-Hexathiadiazocane 1,3-Hexasulfurdiimide	H2N2S6			1003-75-4
1,2,3,4,6,7,5,8-Hexathiadiazocane 1,4-Hexasulfurdiimide	H2N2S6			1003-76-5
1,2,3,5,6,7,4,8-Hexathiadiazocane 1,5-Hexasulfurdiimide	H2N2S6
1,2,3,5,7,4,6,8-Pentathiatriazocane	H3N3S5			638-50-6
	ScNH
	Ga2(NH)3	polymer
	YNH
	BaNH	linear
	LaNH	linear	C∞v
	CeNH	linear	C∞v
Uranimine nitride	N≡U═N−H
Uranimine dihydride	HN═UH2

Molecular imines of other actinides called neptunimine and plutonimine have been postulated to exist in the gas phase or noble gas matrix.