Binary silicon-hydrogen compounds

Chemical structure of disilane, which is structurally similar to ethane.

Silanes are saturated chemical compounds with the empirical formula Si

y. They are hydrosilanes, a class of compounds that includes compounds with Si–H and other Si–X bonds. All contain tetrahedral silicon and terminal hydrides. They only have Si–H and Si–Si single bonds. The bond lengths are 146.0 pm for a Si–H bond and 233 pm for a Si–Si bond. The structures of the silanes are analogues of the alkanes, starting with silane, SiH
4, the analogue of methane, continuing with disilane Si

6, the analogue of ethane, etc. They are mainly of theoretical or academic interest.[1]

Unsaturated comopunds are also known, where silenes have a silicon–silicon double bond and silynes a triple bond, analogous to alkenes and alkynes. Examples include disilene and disilyne. Several constitutional isomers of Si

6 have been analyzed theoretically and been the object of synthetic efforts to compare the nature of the all-silicon silabenzene to benzene and its isomers.

## Contents

* 1 Inventory
* 2 Production
* 3 Applications
* 4 Hazards
* 5 Nomenclature
* 6 See also
* 7 References

## Inventory

Cyclopentasilane is structurally similar to cyclopentane, just larger.

The simplest isomer of a silane is the one in which the silicon atoms are arranged in a single chain with no branches. This isomer is sometimes called the n-isomer (n for "normal", although it is not necessarily the most common). However the chain of silicon atoms may also be branched at one or more silicon atoms. The number of possible isomers increases rapidly with the number of silicon atoms. The members of the series (in terms of number of silicon atoms) follow:

* silane, SiH
4, 1 silicon atom and 4 hydrogen atoms, analogous to methane
* disilane, Si

6 or H
3Si–SiH
3, 2 silicon atoms and 6 hydrogen atoms, analogous to ethane
* trisilane, Si

8 or H
2Si(–SiH

2, 3 silicon atoms and 8 hydrogen atoms, analogous to propane
* tetrasilane, Si

10 or H
3Si–SiH
2–SiH
2–SiH
3, 4 silicon atoms and 10 hydrogen atoms, analogous to butane (one isomer: isotetrasilane, analogous to isobutane)
* pentasilane, Si

12 or H
3Si–SiH
2–SiH
2–SiH
2–SiH
3, 5 silicon atoms and 12 hydrogen atoms, analogous to pentane (two isomers: isopentasilane H
3Si–SiH
2–SiH(–SiH

2 and neopentasilane Si(SiH

4, analogous to isopentane and neopentane, respectively)
* hexasilane Si

14 or H
3Si–SiH
2–SiH
2–SiH
2–SiH
2–SiH
3, 6 silicon atoms and 14 hydrogen atoms, analogous to hexane

Silanes are named by adding the suffix -silane to the appropriate numerical multiplier prefix. Hence, disilane, Si

6; trisilane Si

8; tetrasilane Si

10; pentasilane Si

12; etc. The prefix is generally Greek, with the exceptions of nonasilane which has a Latin prefix, and undecasilane and tridecasilane which have mixed-language prefixes. Solid phase polymeric silicon hydrides called polysilicon hydrides are also known. When hydrogen in a linear polysilene polysilicon hydride is replaced with alkyl or aryl side-groups, the term polysilane is used.

3-Silylhexasilane, H
3Si–SiH
2–SiH(–SiH
3)–SiH
2–SiH
2–SiH
3, is the simplest chiral binary noncyclic silicon hydride.

Cyclosilanes also exist. They are structurally analogous to the cycloalkanes, with the formula Si

2n, n > 2\.

Data for small silanes[1] Silane  | Formula  | Melting point [°C]  | Boiling point [°C]  | Density [g cm−3] (at 25 °C)  | Appearance

|
|
|
|
|

Silane | SiH
4 | −185  | −112  |  | Colorless gas
Disilane | Si

6 | −132  | −14  |  | Colorless gas
Trisilane | Si

8 | −117  | 53  | 0.743  | Colorless liquid
Cyclotrisilane (el)  | Si

6 |  |  |
Tetrasilane (de)  | Si

10 | −90  | 108  | 0.793  | Colorless liquid
Pentasilane (de)  | Si

12 | −72.8  | 153  | 0.827  | Colorless liquid
Cyclopentasilane | Si

10 | −10.5[clarification needed] | 194[clarification needed] | 0.963  | Colorless liquid
Hexasilane (de)  | Si

14 | −44.7  | 193.6  | 0.847  | Colorless liquid
Cyclohexasilane | Si

12 | 16.5  | 226  |  | Colorless liquid

## Production

Early work was conducted by Alfred Stock and Carl Somiesky.[2] Although monosilane and disilane were already known, Stock and Somiesky discovered, beginning in 1916, the next four members of the Si

2n+2 series, up to n = 6. They also documented the formation of solid phase polymeric silicon hydrides.[3] One of their synthesis methods involved the hydrolysis of metal silicides. This method produces a mixture of silanes, which required separation on a high vacuum line.[4][5][6]

The silanes (Si

2n+2) are less thermally stable than alkanes (C

2n+2). They tend to undergo dehydrogenation, yielding hydrogen and polysilanes. For this reason, the isolation of silanes higher than heptasilane has proved difficult.[7]

The Schlesinger process is used to prepare silanes by the reaction of perchlorosilanes with lithium aluminium hydride.

## Applications

The single but significant application for SiH
4 is in the microelectronics industry. By metal organic chemical vapor deposition, silane is converted to silicon by thermal decomposition:

SiH
4 → Si + 2 H

## Hazards

Silane is explosive when mixed with air (1 – 98% SiH
4[clarification needed]). Other lower silanes can also form explosive mixtures with air. The lighter liquid silanes are highly flammable; this risk increases with the length of the silicon chain.

Considerations for detection/risk control:

* Silane is slightly denser than air, while disilane and trisilane are denser than air, thus there is a possibility of pooling at ground levels/pits.
*   *

## Nomenclature

Main article: Chemistry:IUPAC nomenclature of inorganic chemistry 2005

The IUPAC nomenclature (systematic way of naming compounds) for silanes is based on identifying hydrosilicon chains. Unbranched, saturated hydrosilicon chains are named systematically with a Greek numerical prefix denoting the number of silicons and the suffix "-silane".

IUPAC naming conventions can be used to produce a systematic name.

The key steps in the naming of more complicated branched silanes are as follows:

* Identify the longest continuous chain of silicon atoms
* Name this longest root chain using standard naming rules
* Name each side chain by changing the suffix of the name of the silane from "-ane" to "-anyl", except for "silane" which becomes "silyl"
* Number the root chain so that the sum of the numbers assigned to each side group will be as low as possible
* Number and name the side chains before the name of the root chain

The nomenclature parallels that of alkyl radicals.

Silanes can also be named like any other inorganic compound; in this naming system, silane is named silicon tetrahydride. However, with longer silanes, this becomes cumbersome.

## See also

* Organosilicon compounds, compounds containing carbon–silicon bonds
* Hydrosilanes, a larger class of compounds with the formula H
mSiR
n (m ≠ 0)

## References

1. ↑ 1.0 1.1 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 978-0-08-037941-8.
2. ↑ E. Wiberg, Alfred Stock and the Renaissance of Inorganic Chemistry," Pure Appl. Chem., Vol. 49 (1977) pp. 691-700.
3. ↑ J. W. Mellor, "A Comprehensive Treatise on Inorganic and Theoretical Chemistry," Vol. VI, Longman, Green and Co. (1947) pp. 223 - 227.
4. ↑ Hydrides of Boron and Silicon. Ithaca (USA) 1933.
5. ↑ Stock, A.; Stiebeler, P.; Zeidler, F. (1923). "Siliciumwasserstoffe, XVI. Die höheren Siliciumhydride". Ber. Dtsch. Chem. Ges. B 56B (7): 1695–1705. doi:10.1002/cber.19230560735.
6. ↑ P. W. Schenk (1963). "Silanes SiH4 (Si2H6, Si3H8)". in G. Brauer. Handbook of Preparative Inorganic Chemistry, 2nd Ed.. 1. NY, NY: Academic Press. pp. 679–680.
7. ↑ W. W. Porterfield "Inorganic Chemistry: A Unified Approach," Academic Press (1993) p. 219.

* 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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