binary silicon-hydrogen compounds

image:Pentasilolane.svg 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, {{Chem2|SiH4}}, 1 silicon atom and 4 hydrogen atoms, analogous to methane
• disilane, {{Chem2|Si2H6}} or {{chem2|H3Si\sSiH3}}, 2 silicon atoms and 6 hydrogen atoms, analogous to ethane
• trisilane, {{Chem2|Si3H8}} or {{chem2|H2Si(\sSiH3)2}}, 3 silicon atoms and 8 hydrogen atoms, analogous to propane
• tetrasilane, {{Chem2|Si4H10}} or {{chem2|H3Si\sSiH2\sSiH2\sSiH3}}, 4 silicon atoms and 10 hydrogen atoms, analogous to butane (one isomer: isotetrasilane, analogous to isobutane)
• pentasilane, {{Chem2|Si5H12}} or {{chem2|H3Si\sSiH2\sSiH2\sSiH2\sSiH3}}, 5 silicon atoms and 12 hydrogen atoms, analogous to pentane (two isomers: isopentasilane {{chem2|H3Si\sSiH2\sSiH(\sSiH3)2}} and neopentasilane {{chem2|Si(SiH3)4}}, analogous to isopentane and neopentane, respectively)
• hexasilane {{chem2|Si6H14}} or {{chem2|H3Si\sSiH2\sSiH2\sSiH2\sSiH2\sSiH3}}, 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, {{Chem2|Si2H6}}; trisilane {{Chem2|Si3H8}}; tetrasilane {{Chem2|Si4H10}}; pentasilane {{Chem2|Si5H12}}; 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, {{chem2|H3Si\sSiH2\sSiH(\sSiH3)\sSiH2\sSiH2\sSiH3}}, is the simplest chiral binary noncyclic silicon hydride.

Cyclosilanes also exist. They are structurally analogous to the cycloalkanes, with the formula {{chem2|Si_{n}H_{2n}|}}, n > 2.

Early work was conducted by Alfred Stock and Carl Somiesky.E. Wiberg, [http://www.iupac.org/publications/pac/pdf/1977/pdf/4906x0691.pdf Alfred Stock and the Renaissance of Inorganic Chemistry]," Pure Appl. Chem., Vol. 49 (1977) pp. 691-700. Although monosilane and disilane were already known, Stock and Somiesky discovered, beginning in 1916, the next four members of the {{chem2|Si_{n}H_{2n+2}|}} series, up to n = 6. They also documented the formation of solid phase polymeric silicon hydrides.J. W. Mellor, "A Comprehensive Treatise on Inorganic and Theoretical Chemistry," Vol. VI, Longman, Green and Co. (1947) pp. 223 - 227. 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.Hydrides of Boron and Silicon. Ithaca (USA) 1933.{{cite journal|author1=Stock, A. |author2=Stiebeler, P. |author3=Zeidler, F. |title=Siliciumwasserstoffe, XVI. Die höheren Siliciumhydride|journal=Ber. Dtsch. Chem. Ges. B|year=1923|volume=56B|pages=1695–1705|doi=10.1002/cber.19230560735}}{{cite book|chapter=Silanes SiH₄ (Si₂H₆, Si₃H₈)|author=P. W. Schenk|title=Handbook of Preparative Inorganic Chemistry, 2nd Ed.|editor=G. Brauer|publisher=Academic Press|year=1963|place=NY, NY|volume=1|pages=679–680}}

The silanes ({{chem2|Si_{n}H_{2n+2}|}}) are less thermally stable than alkanes ({{chem2|C_{n}H_{2n+2}|}}). They tend to undergo dehydrogenation, yielding hydrogen and polysilanes. For this reason, the isolation of silanes higher than heptasilane has proved difficult.W. W. Porterfield "Inorganic Chemistry: A Unified Approach," Academic Press (1993) p. 219.

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

{{main|Silane#Applications}}

The single but significant application for {{chem2|SiH4}} is in the microelectronics industry. By metal organic chemical vapor deposition, silane is converted to silicon by thermal decomposition:

:{{chem2|SiH4 → Si + 2 H2}}

Silane is explosive when mixed with air (1 – 98% {{chem2|SiH4}}{{clarify|reason=What "%" stands for??? Is it mass, volume or mole fraction??? The writer assumes that the readers can read the writer's mind. Using ambiguous units in science (like "%" "per mille", "parts" or "ppm") without any clear explanation what they stand for is unacceptable!|date=May 2023}}). 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.

{{Main|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.

• Organosilicon compounds, compounds containing carbon–silicon bonds
• Hydrosilanes, a larger class of compounds with the formula {{chem2|H_{m}SiR_{n}|}} (m ≠ 0)

{{Reflist}}

{{Hydrides by group}}

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