Organotin compound
Organotin compounds or stannanes are chemical compounds based on tin with hydrocarbon substituents. Organotin chemistry is part of the wider field of organometallic chemistry. The first organotin compound was diethyltin diiodide ((C2H5)2SnI2), discovered by Edward Frankland in 1849. The area grew rapidly in the 1900s, especially after the discovery of the Grignard reagents, which are useful for producing Sn-C bonds. The area remains rich with many applications in industry and continuing activity in the research laboratory.
Organotin compounds are generally classified according to their oxidation states. Tin(IV) compounds are much more common and more useful.
The tetraorgano derivatives are invariably tetrahedral. Compounds of the type SnRR'RR' have been resolved into individual enantiomers.
Organotin chlorides have the formula R4−nSnCln for values of n up to 4. Bromides, iodides, and fluorides are also known but less important. These compound are known for many R groups. They are always tetrahedral. The tri- and dihalides form adducts with good Lewis bases such as pyridine. The fluorides tend to associate such that dimethyltin difluoride forms sheet-like polymers. Di- and especially triorganotin halides, e.g. tributyltin chloride, exhibit toxicities approaching that of hydrogen cyanide.
Organotin hydrides have the formula R4−nSnHn for values of n up to 4. The parent member of this series, stannane (SnH4), is an unstable colourless gas. Stability is correlates with the number of organic substituents. Tributyltin hydride is used as a source of hydride radical in some organic reactions.
Organotin oxides and hydroxides are common products from the hydrolysis of organotin halides. Unlike the corresponding derivatives of silicon and germanium, tin oxides and hydroxides often adopt structures with penta- and even hexacoordinated tin centres, especially for the diorgano- and monoorgano derivatives. The group Sn-O-Sn is called a stannoxane. Structurally simplest of the oxides and hydroxides are the triorganotin derivatives. A commercially important triorganotin hydroxides is the acaricide Cyhexatin (also called Plictran), (C6H11)3SnOH. Such triorganotin hydroxides exist in equilibrium with the distannoxanes:
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