Phosphine is the common name for phosphorus hydride (PH3), also known by the IUPAC name phosphane and, occasionally, phosphamine. It is a colorless, flammable gas with a boiling point of −88 °C at standard pressure. Pure phosphine is odorless, but "technical grade" phosphine has a highly unpleasant odor like garlic or rotting fish, due to the presence of substituted phosphine and diphosphine (P2H4). Phosphines are also a group of substituted phosphines, with the structure R3P, where other functional groups replace hydrogens. They are important in catalysts where they complex to various metal ions; a chiral metal phosphine complex can catalyze a reaction to give chiral products.
Phosphine is highly toxic; it can easily kill in relatively low concentrations. Because of this, the gas is used for pest control by fumigation. For farm use, it is often sold in the form of aluminium phosphide, calcium phosphide, or zinc phosphide pellets, which yield phosphine on contact with atmospheric water or rodents' stomach acid. These pellets also contain other chemicals which evolve ammonia which helps to reduce the potential for spontaneous ignition or explosion of the phosphine gas. They may also contain other agents, such as methanethiol, to give the gas a detectable garlic smell to help warn against its presence in the atmosphere.
Phosphine is also used as a dopant in the semiconductor industry, and a precursor for the deposition of compound semiconductors. Recently high purity tertiary butyl phosphine (TBP) has been developed as a less hazardous liquid alternative to highly toxic phosphine gas, for application in Metalorganic Vapor Phase Epitaxy (MOVPE) of III-V compound semiconductors.