Organo-tin compounds: Overview
Description
Organotins with four organic groups, e.g. tetrabutyltin, tetraoctyltin and tetraphenyltin, can be used as starting materials or catalysts. Organotins with three organic groups can be powerful fungicides and bactericides, depending on the organic group R. Tributyltins (e.g. TBTO, Incidin) are industrial biocides used in antifouling paints and in wood treatment and preservation. They find use as disinfectants and agents for destroying molluscs such as snails (molluscicides). Other uses include antifungal action in textiles and industrial water systems such as cooling tower and refrigeration water systems, wood pulp and paper mill systems, and breweries. They can also be used for the control of schistosomiasis (a chronic tropical disease). Triphenyltins (e.g. Fentin, Tinmate, Brestanol) are used as agricultural fungicides and in antifouling paints. Other organotins in this class include Plictran, Bay Bue 1452, Vendex and Torque which are used as miticides/acaricides (substances used for killing mites or ticks). Organotins with two organic groups, e.g. dimethyltin, dibutyltin and diestertins, can be used as PVC heat stabilisers, as catalysts, in polyurethane formation and silicon curing, and as heat stabilisers for rigid food-packaging PVC. Organotins with one organic group, e.g. methyltin, butyltin, octyltin and monoestertins, are employed as PVC heat stabilisers. Common uses for selected organotin compounds follow. Tributyltin oxide is used as a fungicide and pesticide in timber treatments. It has been used in antifouling paints but this application is now banned by international protocol. Triphenyltin acetate is used as an insect control agent and a fungicide. Triphenyltin chloride is used as a biocide and an intermediate. Triphenyltin hydroxide is used as a chemical to sterilise insects and as a fungicide. Fenbutatin oxide is used for the control of a wide range of mites which feed on plants. Azocyclotin is a long-acting acaricide for the control of spider mites on fruits (including citrus), vines, hops, cotton, vegetables and ornamentals. Cyhexatin is used as an acaricide/miticide.
Substance details
Substance name: Organo-tin compounds
CASR number: Not applicable
Molecular formula: A large number of organotin compounds exist. Important organotin compounds can belong to any of four classes. These classes are related to the number of organic groups, namely tetraorganotins, triorganotins, diorganotins and monoorganotins.
Synonyms: Organotin compounds include tributyltin or tributylstannane (CASR# 688-73-3), tributyltin oxide or TBTO, tributylstannane, Metatin 50, Biomet (CASR# 56-35-9), triphenyltin (CASR# 668-34-8), triphenyltin acetate or fentin acetate, TPTA, triphenylstannium acetate, Batasan, Brestan, Libromatin, Lirostanol, Phenostat A, Phentinoacetate, Suzu (CASR# 900-95-8), triphenyltin hydroxide or fentin hydroxide, hydroxytriphenylstannane, hydroxytriphenyltin, triphenylstannium hydroxide, triphenyltin oxide, Haitin, Tubotin (CASR# 76-87-9), triphenyltin chloride or fentin chloride, TPTC, chlorotriphenylstannane, chlorotriphenyltin, triphenylchlorostannane, triphenylchlorotin, Aquatin, Brestanol, Phenostat-C, Tinmate (CASR# 639-58-7) fenbutatin oxide or Bendex, Neoxtanox, Osdaran, Torque, Vendex, Shell (CASR# 13356-08-6), azocyclotin or Bay Blue 1452, Peropal (CASR# 41083-11-8), and cyhexatin or TCTH, plictran, tricyclohexylhydroxystannane, tricyclohexylhydroxytin, tricyclohexylstannanol, tricyclohexylstannium hydroxide (CASR# 13121-70-5).
Physical properties
Organotin compounds vary in their physical properties. Properties of selected organotins follow.
- Tributyltin oxide is a thin colourless to yellow liquid with a weak odour. Its specific gravity is 1.17.
- Triphenyltin acetate is an off-white crystalline solid. It melts at 124-126°C.
- Triphenyltin chloride is a white crystalline solid which melts at 103-106°C.
- Triphenyltin hydroxide is an off-white powder which melts at 124-126°C.
- Fenbutatin oxide is a white crystalline solid which is extremely stable to heat, light and atmospheric oxygen. It melts at 138-139°C and its specific gravity is 1.29-1.33.
- Azocyclotin is a colourless crystalline solid which melts at 219°C.
- Cyhexatin is a white crystalline solid that melts at 195-198°C.
Chemical properties
Organotin compounds vary in their chemical and biological properties. Most commercial organotins have a very low water solubility. Some general properties for different classes of organotins follow.
- Tetraorganotins are very stable. They are ineffective as biocides (substances that are capable of killing living organisms) and are relatively non-toxic. However, they can be slowly decomposed or metabolised to more toxic triorganotin compounds.
- Triorganotin compounds are generally more toxic than organotins in other classes. Trialkyltins with linear organic groups cannot be used as agricultural biocides due to their high toxicity to plants (phytotoxicity). Diorganotins show no antifungal activity. Their antibacterial and toxic activity is low, except for the diphenyl derivatives.
- Monoorganotins show no biocidal activity and have very low toxicity to mammals.
Major environmental implications are related to triorganotins used as agricultural and industrial biocides and to a lesser extent to the application of some diorganotin and monoorganotin compounds in rigid PVC. Properties for selected organotin compounds follow.
- Solubility of tributyltin oxide in water is less than 20 ppm. It mixes with organic solvents.
- Triphenyltin acetate does not mix with water. It is soluble in ether.
- Triphenyltin chloride reacts with water.
- Triphenyltin hydroxide does not mix with water.
- Fenbutatin oxide is a triorganotin compound and is almost insoluble in water (0.005 milligram/L at 23°C). It is soluble in acetone, benzene and dichloromethane.
- Azocyclotin is a triorganotin compound. Its solubility in water is less than 1 ppm.
- Cyhexatin is a triorganotin compound. Its solubility in water is less than 1 ppm at 25°C. It is slightly soluble in acetone and soluble in methanol and chloroform.
Further information
The National Pollutant Inventory (NPI) holds data for all sources of organo-tin compounds emissions in Australia.
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