Pnictogen hydride

Short description: Chemical compound with hydrogen and pnictogen atoms

Ammonia, phosphine, and arsine, three simple pnictogen hydrides

Pnictogen hydrides or hydrogen pnictides are binary compounds of hydrogen with pnictogen atoms (elements of group 15: nitrogen, phosphorus, arsenic, antimony, bismuth, and moscovium).

## Contents

* 1 Pnictogen trihydrides
* 2 Dipnictogen tetrahydrides
* 3 Higher derivatives
* 4 Properties
* 5 See also
* 6 References
* 7 Bibliography

## Pnictogen trihydrides

The simplest series has the chemical formula XH3 (less commonly H3X), with X representing any pnictogen. They take on the pyramidal structure (as opposed to the trigonal planar arrangement of the group 13 hydrides), and therefore are polar. These pnictogen trihydrides are generally increasingly unstable and poisonous with heavier elements.

Compound names  | Chemical formula | Geometry  | Space-filling model

|
|
|

nitrogen hydride
hydrogen nitride
ammonia
(azane) | NH
3 | 90px | 100px
phosphorus hydride
hydrogen phosphide
phosphine
(phosphane) | PH
3 | 90px | 90px
arsenic hydride
hydrogen arsenide
arsine
(arsane) | AsH
3 | 90px | 85px
antimony hydride
hydrogen antimonide
stibine
(stibane) | SbH
3 | 90px | 84px
bismuth hydride
hydrogen bismuthide
bismuthine
(bismuthane) | BiH
3 | 90px |
moscovium hydride[1]
hydrogen moscovide
moscovine
(moscovane) | McH
3 |  |

Some properties of the pnictogen trihydrides follow:[2]

Property  | NH
3 | PH
3 | AsH
3 | SbH
3 | BiH

|
|
|
|
|

Melting point (°C)  | −77.8  | −133.5  | −116.3  | −88  | ?
Boiling point (°C)  | −34.5  | −87.5  | −62.4  | −18.4  | 16.8 (extrapolated)
Liquid density (g/cm3)  | 0.683 (−34 °C)  | 0.746 (−90 °C)  | 1.640 (−64 °C)  | 2.204 (−18 °C)  | ?
ΔH°f/kJ mol−1 | −46.1  | +5[3] | +66.4  | +145.1  | +277.8
Distance (X–H)/pm  | 101.7  | 141.9  | 151.9  | 170.7  | 177.59
Angle H–X–H  | 107.8°  | 93.6°  | 91.8°  | 91.3°  | 90.48°

These gases have no smell in pure form, instead gaining it when in contact with air. Ammonia has an infamous, intense odour resembling urine or fish, commonly the result of the decomposition of urea. Phosphine, arsine, and stbine smell like fish or garlic.

## Dipnictogen tetrahydrides

Dipnictogen tetrahydrides have the chemical formula X

4. These are generally less stable than the trihydrides, commonly decomposing to the trihydride and the pnictogen involved.

Compound names  | Chemical formula | Geometry  | Space-filling model

|
|
|

dinitrogen hydride
hydrazine
(diazane) | N2H4 | 90px | 100px
diphosphorus hydride
diphosphine
(diphosphane) | P2H4 | 90px | 100px
diarsenic hydride[2]
diarsine
(diarsane) | As2H4 |  |

## Higher derivatives

Polyphosphanes exist with the formula PnHn+2 (n = 1–9). Linear and branch isomers of P

6 have been detected. Other cyclic and condensed polyphosphane series are known, from PnHn to PnHn−18, amounting to 85 known phosphanes in 1997.[4]

## Properties

Noncyclic hydrogen pnictides follow the formula XnHn+2.

Models of phosphanes of lengths 3 and 4

Ammonia is produced industrially on the largest scale among all compounds. Like water and hydrogen fluoride, hydrogen bonding results in a high melting and boiling point compared to the other pnictogen hydrides, although 26% is lost on melting, another 7% as the liquid is heated to boiling, and the remaining 67% upon boiling. Other effects of hydrogen bonding are a high dielectric constant as well as low values of density, viscosity, and electrical conductivity. Like water, it is an excellent and often-used ionising solvent.[5] Over twenty other hydrides of nitrogen are known, the most important being hydrazine (N2H4) and hydrogen azide (HN3). Hydrazine has physical properties that are similar to those of water: its melting and boiling points are 2.0 °C and 113.5 °C, the density of the solid at −5 °C is 1.146 g/cm3, while that of the liquid at 25 °C is 1.00 g/cm3.[6] The azanes are a series which include ammonia, hydrazine and triazane.

Phosphine, a toxic, colourless gas, is the most stable phosphorus hydride. It is insoluble in water but soluble in organic liquids (as well as carbon disulfide and trichloroacetic acid). Phosphine is a reducing agent.[4]

Arsine, stibine, and bismuthine are highly toxic, thermally unstable, and colourless gases. No appreciable hydrogen bonding is found in phosphine, arsine, stibine or bismuthine, and there is no appreciable tendency to dissociate like ammonia to MH+4 and MH−2 (M = P, As, Sb, Bi). The pnictogen hydrides become denser down the group and the M–H bond lengths increase, while the H–M–H bond angle decreases slightly. The standard enthalpies of formation reflect the increasing thermal instability going down the group. Arsine decomposes to arsenic and hydrogen at 250–300 °C, stibine to antimony and hydrogen at room temperature, and bismuthine to bismuth and hydrogen above −60 °C. Arsine and stibine are very easily oxidised to arsenic or antimony trioxide and water; a similar reaction happens with sulfur or selenium. Reaction with metals at elevated temperatures leads to arsenides and antimonides. A few lower hydrides are known, such as As2H4, but they are even more unstable and their properties are unknown.[2]

Imidogen, a radical composed of one hydrogen atom and one nitrogen atom (NH), can be classed as a pnictogen hydride.

## See also

Note: This topic belongs to "Chemistry " portal

* Ammonium
* Hydrazoic acid
* Hydrogen halide

## References

1. ↑ Santiago, Régis T.; Haiduke, Roberto L. A. (2018). "Relativistic effects on inversion barriers of pyramidal group 15 hydrides". International Journal of Quantum Chemistry 118 (14). doi:10.1002/qua.25585.
2. ↑ 2.0 2.1 2.2 Greenwood and Earnshaw, pp. 557–8
3. ↑ Zumdahl, Steven S. (2009). Chemical Principles (6th ed.). Houghton Mifflin. p. A22. ISBN 978-0-618-94690-7.
4. ↑ 4.0 4.1 Greenwood and Earnshaw, pp. 492–3
5. ↑ Greenwood and Earnshaw, pp. 420–4
6. ↑ Greenwood and Earnshaw, pp. 426–7

## Bibliography

* Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.

* v
* t
* e

Binary compounds of hydrogen

Alkali metal (Group 1) hydrides|

* LiH
* NaH
* KH
* RbH
* CsH

Lithium hydride, LiH
ionic metal hydride

Beryllium hydride
Left (gas phase): BeH2
covalent metal hydride
Right: (BeH2)n (solid phase)
polymeric metal hydride

Borane and diborane
Left: BH3 (special conditions), covalent metalloid hydride
Right: B2H6 (standard conditions), dimeric metalloid hydride

Methane, CH4
covalent nonmetal hydride

Ammonia, NH3
covalent nonmetal hydride

Water, H2O
covalent nonmetal hydride

Hydrogen fluoride, HF
covalent nonmetal hydride

Alkaline (Group 2) earth hydrides|

| Monohydrides|

* BeH
* MgH
* CaH
* SrH
* BaH

|

Dihydrides|

* BeH2
* MgH2
* CaH2
* SrH2
* BaH2

|

Group 13 hydrides|

| Boranes|

* BH3
* B2H6
* B2H2
* B2H4
* B4H10
* B5H9
* B5H11
* B6H10
* B6H12
* B10H14
* B18H22

|

Alanes|

* AlH3
* Al2H6

|

Gallanes|

* GaH3
* Ga2H6

|

Indiganes|

* InH3
* In2H6

|

Thallanes|

* TlH3
* Tl2H6

|

Group 14 hydrides|

| Linear alkanes|

* CH4
* C2H6
* C3H8
* C4H10
* C5H12
* C6H14
* C7H16
* C8H18
* C9H20
* C10H22
* more...

|

Linear alkenes|

* C2H4
* C3H6
* C4H8
* C5H10
* C6H12
* C7H14
* C8H16
* C9H18
* C10H20
* more...

|

Linear alkynes|

* C2H2
* C3H4
* C4H6
* C5H8
* C6H10
* C7H12
* C8H14
* C9H16
* C10H18
* more...

|

Silanes|

* SiH4
* Si2H6
* Si3H8
* Si4H10
* Si5H12
* Si6H14
* Si7H16
* Si8H18
* Si9H20
* Si10H22
* more...

|

Silenes|

* Si2H4

|

Silynes|

* Si2H2
* SiH

|

Germanes|

* GeH4
* Ge2H6
* Ge3H8
* Ge4H10
* Ge5H12

|

Stannanes|

* SnH4
* Sn2H6

|

Plumbanes|

* PbH4

|

* CH
* CH2
* CH3
* C2H
* Cycloalkanes
* Cycloalkenes
* Annulenes
* Many more

Pnictogen (Group 15) hydrides|

| Azanes|

* NH3
* N2H4
* N3H5
* N4H6
* N5H7
* N6H8
* N7H9
* N8H10
* N9H11
* N10H12
* more...

|

Azenes|

* N2H2
* N3H3
* N4H4

|

Phosphanes|

* PH3
* P2H4
* P3H5
* P4H6
* P5H7
* P6H8
* P7H9
* P8H10
* P9H11
* P10H12
* more...

|

Phosphenes|

* P2H2
* P3H3
* P4H4

|

Arsanes|

* AsH3
* As2H4

|

Stibanes|

* SbH3

|

Bismuthanes|

* BiH3

|

* HN3
* NH
* radical

Hydrogen chalcogenides (Group 16 hydrides)|

| Polyoxidanes|

* H2O
* H2O2
* H2O3
* H2O4
* H2O5
* H2O6
* H2O7
* H2O8
* H2O9
* H2O10
* more...

|

Polysulfanes|

* H2S
* H2S2
* H2S3
* H2S4
* H2S5
* H2S6
* H2S7
* H2S8
* H2S9
* H2S10
* more...

|

Selanes|

* H2Se
* H2Se2

|

Tellanes|

* H2Te
* H2Te2

|

Polanes|

* PoH2

|

* HO
* HO2
* HO3
* H2O+–O–
* H2S=S
* (HS)2S+–S–
* HS
* HDO
* D2O
* T2O

Hydrogen halides (Group 17 hydrides)|

* HF
* HCl
* HBr
* HI
* HAt

Transition metal hydrides|

* ScH2
* YH2
* YH3
* TiH2
* ZrH2
* HfH2
* VH
* VH2
* NbH
* NbH2
* TaH
* CrH
* CrH2
* CrHx
* NiH
* PdHx (x < 1)
* FeH
* FeH2
* FeH5
* CuH
* ZnH2
* CdH2
* HgH2

Lanthanide hydrides|

* LaH2
* LaH3
* LaH10
* CeH2
* CeH3
* PrH2
* PrH3
* NdH2
* NdH3
* SmH2
* SmH3
* EuH2
* GdH2
* GdH3
* TbH2
* TbH3
* DyH2
* DyH3
* HoH2
* HoH3
* ErH2
* ErH3
* TmH2
* TmH3
* YbH2
* YbH2.5
* LuH2
* LuH3

Actinide hydrides|

* AcH2
* ThH2
* Th4H15
* PaH3
* UH3
* NpH2
* NpH3
* PuH2
* PuH3
* AmH2
* AmH3
* CmH2

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