silanes

Silanes are a class of chemical compounds containing silicon bonded to hydrogen or to hydrocarbon substituents. The simplest saturated silanes have the formula Si_nH_{2n+2} (n ≥ 1), with silane (SiH4) as the prototypical member. Organosilanes replace some hydrogens with alkyl or aryl groups, for example trimethylsilane. Silanes are typically covalent, and silicon often adopts a tetrahedral geometry in many species.

Silanes span a range of physical properties; many are volatile gases or low-boiling liquids. The Si–H bond is relatively reactive toward oxidation and moisture, and Si–H can act as a mild reducing agent under catalytic conditions. Hydrolysis of silanes yields silanols and hydrogen, and can lead to subsequent condensation to siloxanes and silica. Higher silanes can undergo oligomerization or dehydrogenation at elevated temperatures.

Production and scope: Industrial preparation often involves the reduction of silicon halides, such as SiCl4, with metal hydrides (for example lithium aluminium hydride) to give silane (SiH4), which can be used to synthesize higher silanes or a variety of organosilicon compounds. Silanes are also central to silicone chemistry and to hydrosilylation, a set of reactions that adds Si–H across unsaturated substrates to form Si–C or Si–heteroatom bonds.

Applications and safety: Silanes serve as reagents in organic synthesis (including mild hydride donors) and as precursors for silicon-containing polymers, coatings, and films via processes such as chemical vapor deposition. Many silanes are flammable; some, including SiH4, are highly reactive with air and moisture and can be pyrophoric. Handling typically requires inert atmospheres, proper ventilation, and appropriate safety precautions.