Nitrogen pentahydride

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Nitrogen pentahydride
Nitrogen pentahydride possible structure 3D-vdW.png
A possible structure of nitrogen pentahydride according to theory calculations [1]
Other names
Ammonium hydride
3D model (JSmol)
  • [NH5]
  • [H-].[NH4+]
Molar mass 19.047 g·mol−1
Trigonal bipyramidal molecular geometry (covalent [1] )
0 D (covalent [1] )
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Nitrogen pentahydride, also known as ammonium hydride is a hypothetical compound with the chemical formula NH5. There are two theoretical structures of nitrogen pentahydride. One structure is trigonal bipyramidal molecular geometry type NH5 molecule. Its nitrogen atom and hydrogen atoms are covalently bounded, and its symmetry group is D3h. [1] Another predicted structure of nitrogen pentahydride is an ionic compound, make up of an ammonium ion and a hydride ion (NH4+H). Until now, no one has synthesized this substance, or proved its existence, and related experiments have not directly observed nitrogen pentahydride. It is only speculated that it may be a reactive intermediate based on reaction products. Theoretical calculations show this molecule is thermodynamically unstable. [4] The reason might be similar to the instability of nitrogen pentafluoride, [5] so the possibility of its existence is low. However, nitrogen pentahydride might exist in special conditions or high pressure. Nitrogen pentahydride was considered for use as a solid rocket fuel for research in 1966. [6]


Research and attempts

Some studies believe that nitrogen pentahydride may exist in the formation of other metal atoms crystal lattice, such as mercury [7] [8] and lithium. There are also related studies to explore the possibility of a substitution reaction with ammonium halide. [9] There are also attempts to react ammonium and deuterium to produce the pentahydride, however some experiments show that it may only be a reactive intermediate, which will immediately decompose into ammonia and hydrogen, [10] [1] and the same is true for experiments using deuterium. [2] [1] However, all the studies above are only theoretical calculations, the existence of nitrogen pentahydride has not been observed, and this substance has not been shown to exist.

An experimental attempted to do a displacement reaction between ammonium trifluoroacetate and lithium hydride in the molten state, in order to study the possibility of the existence of nitrogen pentahydride: [10]


In the reaction between ammonium trifluoroacetate and lithium deuteride, the product ammonia contains 85% of ordinary ammonia and 15% of monodeuterated ammonia. The product hydrogen contains 66% of hydrogen deuteride, 21% of hydrogen gas and 13% of deuterium gas. In the product collected using tetradeuterated ammonium trifluoroacetate and lithium hydride, ammonia contains ND3, NHD2 and NH2D, while hydrogen contains 68% of hydrogen deuteride, 18% of hydrogen gas and 14% of deuterium gas. Therefore, it is speculated that the reaction may have two routes: one is to directly decompose into ammonia and hydrogen, the other is to first generate ammonium deuteride reactive intermediates, partly by forming deuterium anions and hydrogen cations to form deuterated hydrogen and ammonia and by the formation of hydride ions or deuterium cations to decompose into hydrogen or deuterium gas. [1]

But it immediately decomposed into hydrogen and ammonia, and it was impossible to prove its existence. Experiments with deuterium still get the same results: [2]

[NH4H] → NH3 + H2


Possible structures of covalently bounded nitrogen pentahydride Nitrogen pentahydride possible structures.svg
Possible structures of covalently bounded nitrogen pentahydride

Several papers have conducted theoretical calculations on nitrogen pentahydride, and believe that nitrogen pentahydride is unlikely to form ionic crystals of hydride and ammonium ions. However, it is possible that hydrogen is connected to one of the hydrogen atoms of ammonium. [1] It may also be similar to nitrogen pentafluoride, forming a three-center two-electron bond similar to carbonium ions, or those five hydrogen atoms are arranged in a triangular bipyramid structure around the nitrogen atom. [1]

A compound that is similar to nitrogen pentahydride is the theretical nitrogen pentafluoride. Its structure is assumed to be tetrafluoroammonium fluoride (NF4+F). [11] Similarly to nitrogen pentahydride, it is a compound of nitrogen and five of the same atom, but nitrogen pentafluoride is also a hypothetical compound, still never synthesized and only theoretical research exist. [12] Other pnictogen pentahydrides are theretically more stable, such as phosphorus pentahydride (PH4H) which is more stable than nitrogen pentahydride but still unstable to decomposition to phosphine and hydrogen gas. Its organic derivatives (phosphoranes) are more stable, such as stable pentaphenylphosphorus (Ph5P). [13] Other heavier pnictogen pentahydrides are more likely to exist, such as the theoretical arsenic pentahydride. [14] [ better source needed ]

Related Research Articles

<span class="mw-page-title-main">Ammonia</span> Chemical compound (NH₃)

Ammonia is an inorganic compound of nitrogen and hydrogen with the formula NH3. A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous waste, particularly among aquatic organisms, and it contributes significantly to the nutritional needs of terrestrial organisms by serving as a precursor to 45% of the world's food and fertilizers. Around 70% of ammonia is used to make fertilisers in various forms and composition, such as urea and Diammonium phosphate. Ammonia in pure form is also applied directly into the soil.

In chemistry, amines are compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are formally derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines, trimethylamine, and aniline. Inorganic derivatives of ammonia are also called amines, such as monochloramine.

<span class="mw-page-title-main">Nitrogen</span> Chemical element, symbol N and atomic number 7

Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at seventh in total abundance in the Milky Way and the Solar System. At standard temperature and pressure, two atoms of the element bond to form N2, a colorless and odorless diatomic gas. N2 forms about 78% of Earth's atmosphere, making it the most abundant uncombined element. Nitrogen occurs in all organisms, primarily in amino acids (and thus proteins), in the nucleic acids (DNA and RNA) and in the energy transfer molecule adenosine triphosphate. The human body contains about 3% nitrogen by mass, the fourth most abundant element in the body after oxygen, carbon, and hydrogen. The nitrogen cycle describes the movement of the element from the air, into the biosphere and organic compounds, then back into the atmosphere.

<span class="mw-page-title-main">Ammonium</span> Polyatomic ion (NH₄, charge +1)

The ammonium cation is a positively charged polyatomic ion with the chemical formula NH+4 or [NH4]+. It is formed by the protonation of ammonia. Ammonium is also a general name for positively charged (protonated) substituted amines and quaternary ammonium cations, where one or more hydrogen atoms are replaced by organic or other groups.

In chemistry, a hydride is formally the anion of hydrogen (H). The term is applied loosely. At one extreme, all compounds containing covalently bound H atoms are called hydrides: water (H2O) is a hydride of oxygen, ammonia is a hydride of nitrogen, etc. For inorganic chemists, hydrides refer to compounds and ions in which hydrogen is covalently attached to a less electronegative element. In such cases, the H centre has nucleophilic character, which contrasts with the protic character of acids. The hydride anion is very rarely observed.

<span class="mw-page-title-main">Dinitrogen pentoxide</span> Chemical compound

Dinitrogen pentoxide is the chemical compound with the formula N2O5. It is one of the binary nitrogen oxides, a family of compounds that only contain nitrogen and oxygen. It exists as colourless crystals that sublime slightly above room temperature, yielding a colorless gas.

<span class="mw-page-title-main">Devarda's alloy</span> Chemical compound

Devarda's alloy, is an alloy of aluminium (44% – 46%), copper (49% – 51%) and zinc (4% – 6%).

<span class="mw-page-title-main">Lithium hydride</span> Chemical compound

Lithium hydride is an inorganic compound with the formula LiH. This alkali metal hydride is a colorless solid, although commercial samples are grey. Characteristic of a salt-like (ionic) hydride, it has a high melting point, and it is not soluble but reactive with all protic organic solvents. It is soluble and nonreactive with certain molten salts such as lithium fluoride, lithium borohydride, and sodium hydride. With a molar mass of 7.95 g/mol, it is the lightest ionic compound.

<span class="mw-page-title-main">Lithium nitride</span> Chemical compound

Lithium nitride is a compound with the formula Li3N. It is the only stable alkali metal nitride. The solid has a reddish-pink color and high melting point.

The chemical element nitrogen is one of the most abundant elements in the universe and can form many compounds. It can take several oxidation states; but the most oxidation states are -3 and +3. Nitrogen can form nitride and nitrate ions. It also forms a part of nitric acid and nitrate salts. Nitrogen compounds also have an important role in organic chemistry, as nitrogen is part of proteins, amino acids and adenosine triphosphate.

In chemistry, an onium ion is a cation formally obtained by the protonation of mononuclear parent hydride of a pnictogen, chalcogen, or halogen. The oldest-known onium ion, and the namesake for the class, is ammonium, NH+4, the protonated derivative of ammonia, NH3.

The Chichibabin reaction is a method for producing 2-aminopyridine derivatives by the reaction of pyridine with sodium amide. It was reported by Aleksei Chichibabin in 1914. The following is the overall form of the general reaction:

<span class="mw-page-title-main">Positronium hydride</span> Exotic molecule consisting of a hydrogen atom bound to a positronium atom

Positronium hydride, or hydrogen positride is an exotic molecule consisting of a hydrogen atom bound to an exotic atom of positronium. Its formula is PsH. It was predicted to exist in 1951 by A Ore, and subsequently studied theoretically, but was not observed until 1990. R. Pareja, R. Gonzalez from Madrid trapped positronium in hydrogen laden magnesia crystals. The trap was prepared by Yok Chen from the Oak Ridge National Laboratory. In this experiment the positrons were thermalized so that they were not traveling at high speed, and they then reacted with H ions in the crystal. In 1992 it was created in an experiment done by David M. Schrader and F.M. Jacobsen and others at the Aarhus University in Denmark. The researchers made the positronium hydride molecules by firing intense bursts of positrons into methane, which has the highest density of hydrogen atoms. Upon slowing down, the positrons were captured by ordinary electrons to form positronium atoms which then reacted with hydrogen atoms from the methane.

<span class="mw-page-title-main">Tetrafluoroammonium</span>

The tetrafluoroammonium cation is a positively charged polyatomic ion with chemical formula NF+
. It is equivalent to the ammonium ion where the hydrogen atoms surrounding the central nitrogen atom have been replaced by fluorine. Tetrafluoroammonium ion is isoelectronic with tetrafluoromethane CF
, trifluoramine oxide ONF
and the tetrafluoroborate BF

Uranium hydride, also called uranium trihydride (UH3), is an inorganic compound and a hydride of uranium.

Nitrogen pentafluoride (NF5) is a theoretical compound of nitrogen and fluorine that is hypothesized to exist based on the existence of the pentafluorides of the atoms below nitrogen in the periodic table, such as phosphorus pentafluoride. Theoretical models of the nitrogen pentafluoride molecule are either a trigonal bipyramidal covalently bound molecule with symmetry group D3h, or NF+
F, which would be an ionic solid.

Pnictogen hydrides or hydrogen pnictides are binary compounds of hydrogen with pnictogen atoms covalently bonded to hydrogen.

Carbohydrides are solid compounds in one phase composed of a metal with carbon and hydrogen in the form of carbide and hydride ions. The term carbohydride can also refer to a hydrocarbon.

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).

Protactinium compounds are compounds containing the element protactinium. These compounds usually have protactinium in the +5 oxidation state, although these compounds can also exist in the +2, +3 and +4 oxidation states.


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