Organotin compounds are those with tin linked to hydrocarbons.
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.[1]
Contents
- 1 Structure of organotin compounds
- 1.1 Organic derivatives of tin(IV)
- 1.1.1 Organotin halides and hydrides
- 1.1.2 Organotin oxides and hydroxides
- 1.1.3 Hypercoordinated stannanes
- 1.1.4 Triorganotin cations
- 1.2 Tin radicals (organic derivatives of tin(III))
- 1.3 Organic derivatives of tin(II)
- 1.4 Organic derivatives of tin(I)
- 2 Preparation of organotin compounds
- 3 Reactions of organotin compounds
- 4 Applications
- 4.1 Biological applications
- 5 Toxicity
- 6 See also
- 7 References
- 8 External links
Structure of organotin compounds
Organotin compounds are generally classified according to their oxidation states. Tin(IV) compounds are much more common and more useful.
Organic derivatives of tin(IV)
The entire series R4−nSnCln are known for many R groups and values of n up to 4. The tetraorgano derivatives are invariably tetrahedral. Compounds of the type SnRR'RR' have been resolved into individual enantiomers.[2]
Organotin halides and hydrides
The mixed organic-chloro compounds are also tetrahedral, although they form adducts with good Lewis bases such as pyridine. The fluoride tend to associate such that dimethyltin difluoride forms sheet-like polymers. The mixed organic tin hydrides, e.g. dialkyltin dihydride, are also generally monomeric. The parent member of this series, stannane (SnH4), is an unstable colourless gas.
Organotin oxides and hydroxides
Main article: Stannoxane
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:
- 2 R3SnOH R3SnOSnR3 + H2O
With only two organic substituents on each Sn centre, the diorganotin oxides and hydroxides are structurally more complex than the triorgano derivatives.[3] The simple geminal diols (R2Sn(OH)2) and monomeric stannanones (R2Sn=O) are unknown. Diorganotin oxides (R2SnO) are polymers except when the organic substituents are very bulky, in which case cyclic trimers or, in the case of R = CH(SiMe3)2 dimers, with Sn3O3 and Sn2O2 rings. The distannoxanes exist as dimers of dimers with the formula [R2SnX]2O2 wherein the X groups (e.g., chloride, hydroxide, carboxylate) can be terminal or bridging (see Table). The hydrolysis of the monoorganotin trihalides has the potential to generate stannanoic acids, RSnO2H. As for the diorganotin oxides/hydroxides, the monoorganotin species form structurally complex because of the occurrence of dehydration/hydration, aggregation. Illustrative is the hydrolysis of butyltin trichloride to give [(BuSn)12O14(OH)6]2+.
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Idealized structure of trimeric diorganotin oxide.
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Ball-and-stick model for (t-Bu2SnO)3.
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Structure of diorganotin oxide, highlighting the extensive intermolecular bonding.
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Hypercoordinated stannanes
Unlike carbon(IV) analogues but somewhat like silicon compounds, tin(IV) can also be coordinated to five and even six atoms instead of the regular four. These hypercoordinated compounds usually have electronegative substituents. Numerous examples of hypervalency are provided by the organotin oxides and associated carboxylates and related pseudohalide derivatives.[3] The organotin halides for adducts, e.g. Me2SnCl2(bipyridine.
The all-organic penta- and hexaorganostannates have even been characterized,[4] while in the subsequent year a six-coordinated tetraorganotin compound was reported.[5] A crystal structure of room-temperature stable (in argon) all-carbon pentaorganostannane was reported as the lithium salt with this structure:[6]
In this distorted trigonal bipyramidal structure the carbon to tin bond lengths (2.26 Å apical, 2.17 Å equatorial) are larger than regular C-Sn bonds (2.14 Å) reflecting its hypervalent nature.
Triorganotin cations
Some reactions of triorganotin halides implicate a role for R3Sn+ intermediates. Such cations are analogous to carbocations. They have been characterized crystallographically when the organic substituents are large, such as 2,4,6-triisopropylphenyl.[7]
Tin radicals (organic derivatives of tin(III))
Tin radicals, with the formula R3Sn, are called stannyl radicals.[1] They are invoked as intermediates in certain atom-transfer reactions. For example, tributyltin hydride (tri-n-butylstannane) serves as a useful source of "hydrogen atoms" because of the stability of the tributytin radical.[8]
Organic derivatives of tin(II)
Organotin(II) compounds are somewhat rare. Compounds with the empirical formula SnR2 are somewhat fragile and exist as rings or polymers when R is not bulky. The polymers, called polystannanes, have the formula (SnR2)n.
In principle divalent tin compounds might be expected to form analogues of alkenes with a formal double bond. Indeed compounds with the formula Sn2R4, called distannenes, are known for certain organic substituents. The Sn centres tend to be highly pyramidal. Monomeric compounds with the formula SnR2, analogues of carbenes are also known in a few cases. One example is Sn(SiR3)2, where R is the very bulky CH(SiMe3)2 (Me = methyl). Such species reversibly dimerize to the distannylene upon crystallization:[9]
- 2 R2Sn (R2Sn)2
Stannenes, compounds with tin–carbon double bonds, are exemplified by derivatives of stannabenzene. Stannoles, structural analogs of cyclopentadiene, exhibit little C-Sn double bond character.
Organic derivatives of tin(I)
Compounds of Sn(I) are rare and only observed with very bulky ligands. One prominent family of cages is accessed by pyrolysis of the 2,6-diethylphenyl-substituted tristannylene [Sn(C6H3-2,6-Et2)2]3, which affords the cubane and a prismane. These cages contain Sn(I) and have the formula [Sn(C6H3-2,6-Et2)]n where n = 8, 10.[10] A stannyne contains a carbon to tin triple bond and a distannyne a triple bond between two tin atoms (RSnSnR). Distannynes only exist for extremely bulky substituents. Unlike alkynes, the C-Sn-Sn-C core of these distannynes are nonlinear, although they are planar. The Sn-Sn distance is 3.066(1) Å, and the Sn-Sn-C angles are 99.25(14)°. Such compounds are prepared by reduction of bulky aryltin(II) halides.[11]
Structure of an Ar
10Sn
10 "prismane", a compound containing Sn(I) (Ar = 2,6-diethylphenyl).
Preparation of organotin compounds
Organotin compounds can be synthesised by numerous methods.[12] Classic is the reaction of a Grignard reagent with tin halides for example tin tetrachloride. An example is provided by the synthesis of tetraethyltin:[13]
- 4 EtMgBr + SnCl4 → Et4Sn + 4 MgClBr
The symmetrical tetraorganotin compounds can then be converted to various mixed chlorides by redistribution reactions (also known as the "Kocheshkov comproportionation"):
- 3 R4Sn + SnCl4 → 4 R3SnCl
- R4Sn + SnCl4 → 2 R2SnCl2
- R4Sn + 3 SnCl4 → 4 RSnCl3
A related method involves redistribution of tin halides with organoaluminium compounds.
The mixed organo-halo tin compounds can be converted to the mixed organic derivatives, as illustrated by the synthesis of dibutyldivinyltin:[14]
- Bu2SnCl2 + 2 C2H3MgBr → Bu2Sn(C2H3)2 + 2 MgBrCl
The organotin hydrides are generated by reduction of the mixed alkyl chlorides. For example, treatment of dibutyltin dichloride with lithium aluminium hydride gives the dibutyltin dihydride, a colourless distillable oil:[15]
- Bu2SnCl2 + 1/2 LiAlH4 → Bu2SnH2 + 1/2 LiAlCl4"
The Wurtz-like coupling of alkyl sodium compounds with tin halides yields tetraorganotin compounds.
Reactions of organotin compounds
Important reactions, discussed above, usually focus on organotin halides and pseudohalides with nucleophiles and nucleophiles. In the area of organic synthesis, the Stille reaction is considered important. It entails coupling reaction with sp2-hybridized organic halides catalyzed by palladium:
and organostannane additions (nucleophilic addition of an allyl-, allenyl-, or propargylstannanes to an aldehydes and imines). Organotin compounds are also used extensively in radical chemistry (e.g. radical cyclizations, Barton–McCombie deoxygenation, Barton decarboxylation, etc.).
Applications
An organotin compound is commercially applied as stabilizers in polyvinyl chloride. In this capacity, they suppress degradation by removing allylic chloride groups and by absorbing hydrogen chloride. This application consumes about 20,000 tons of tin each year. The main class of organotin compounds are diorganotin dithiolates with the formula R2Sn(SR')2. The Sn-S bond is the reactive component. Diorganotin carboxylates, e.g., dibutyltin dilaurate, are used as catalysts for the formation of polyurethanes, for vulcanization of silicones, and transesterification.[1]
n-Butyltin trichloride is used in the production of tin dioxide layers on glass bottles by chemical vapor deposition.
Biological applications
"Tributyltins" are used as industrial biocides, e.g. as antifungal agents in textiles and paper, wood pulp and paper mill systems, breweries, and industrial cooling systems. Triphenyltin derivativess are used as active components of antifungal paints and agricultural fungicides. Other triorganotins are used as miticides and acaricides. Tributyltin oxide has been extensively used as a wood preservative.[1][1]
Tributyltin compounds were once widely used as marine anti-biofouling agents to improve the efficiency of ocean-going ships. Concerns over toxicity[16] of these compounds (some reports describe biological effects to marine life at a concentration of 1 nanogram per liter) led to a worldwide ban by the International Maritime Organization.
Organotin complexes have been studied in anticancer therapy.[17]
- Organotin compounds
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Tetrabutyltin starting material for the di- and tributyl compounds
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Tributyltin oxide, a colorless to pale yellow liquid used in wood preservation
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Triphenyltin acetate, an off-white crystalline solid, used as an insecticide and a fungicide
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Triphenyltin chloride, a white crystalline solid, used as a biocide and an intermediate in chemical synthesis
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Trimethyltin chloride also a biocide
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Triphenyltin hydroxide, an off-white powder, used as a fungicide and to sterilize insects
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Azocyclotin, a colorless crystalline solid, used as a long-acting acaricide for control of spider mites on plants
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Cyhexatin, a white crystalline solid, used as an acaricide and miticide
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Hexamethylditin used as an intermediate in chemical synthesis
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Tetraethyltin, boiling point 63–65° /12 mm is a catalyst[18]
Toxicity
Triorganotin compounds can be highly toxic. Tri-n-alkyltins are phytotoxic and therefore cannot be used in agriculture. Depending on the organic groups, they can be powerful bactericides and fungicides. Reflecting their high bioactivity, "tributyltins" were once used in marine anti-fouling paint.[1]
Tetraorgano-, diorgano-, and monoorganotin compounds generally exhibit low toxicity and low biological activity. DBT may however be immunotoxic.[19]
See also
- Organostannane addition
- Tributyltin azide
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References
- ^ a b c d e f Davies, Alwyn George. (2004) Organotin Chemistry, 2nd Edition Weinheim: Wiley-VCH. ISBN 978-3-527-31023-4
- ^ Gielen, Marcel (1973). "From kinetics to the synthesis of chiral tetraorganotin compounds". Acc. Chem. Res. 6: 198–202. doi:10.1021/ar50066a0.
- ^ a b Vadapalli Chandrasekhar, Selvarajan Nagendran, Viswanathan Baskar "Organotin assemblies containing Sn/O bonds" Coordination Chemistry Reviews 2002, vol. 235, 1-52. doi:10.1016/S0010-8545(02)00178-9
- ^ Reich, Hans J.; Phillips, Nancy H. (1986). "Lithium-Metalloid Exchange Reactions. Observation of Lithium Pentaalkyl/aryl Tin Ate Complexes". J. Am. Chem. Soc. 108: 2102. doi:10.1021/ja00268a067.
- ^ V. G. Kumar Das, Lo Kong Mun, Chen Wei, Thomas C. W. Mak (1987). "Synthesis, Spectroscopic Study, and X-ray Crystal Structure of Bis[3-(2-pyridyl)-2-thienyl-C,N]diphenyltin(IV): The First Example of a Six-Coordinate Tetraorganotin Compound". Organometallics 6: 10. doi:10.1021/om00144a003.
- ^ Masaichi Saito, Sanae Imaizumi, Tomoyuki Tajima, Kazuya Ishimura, and Shigeru Nagase (2007). "Synthesis and Structure of Pentaorganostannate Having Five Carbon Substituents". J. Am. Chem. Soc. 129: 10974–10975. doi:10.1021/ja072478.
- ^ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. ISBN 0080379419.
- ^ T. V. RajanBabu, P. C. B. Page B. R. Buckley "Tri-n-butylstannane" in e-EROS Encyclopedia of Reagents for Organic Synthesis, 2004. doi:10.1002/047084289X.rt181.pub2
- ^ Holleman, A. F.; Wiberg, E. (2001), Inorganic Chemistry, San Diego: Academic Press, ISBN 0-12-352651-5
- ^ Lawrence R. Sita "Heavy-Metal Organic Chemistry: Building with Tin" Acc. Chem. Res., 1994, volume 27, pp 191–197. doi: 10.1021/ar00043a002
- ^ Philip P. Power "Bonding and Reactivity of Heavier Group 14 Element Alkyne Analogues" Organometallics 2007, volume 26, pp 4362–4372. doi:10.1021/om700365p
- ^ Sander H.L. Thoonen, Berth-Jan Deelman, Gerard van Koten (2004). "Synthetic aspects of tetraorganotins and organotin(IV) halides" (PDF). Journal of Organometallic Chemistry (689): 2145–2157.
- ^ G. J. M. Van Der Kerk, J. G. A. Luijten "Tetraethyltin" Org. Synth. 1956, volume 36, page 86ff. doi:10.15227/orgsyn.036.0086
- ^ Dietmar Seyferth "Di-n-butyldivinyltin" Org. Synth. 1959, volume 39, page 10. doi:10.15227/orgsyn.039.0010
- ^ "Organometallic Syntheses: Nontransition-Metal Compounds" John Eisch, Ed. Academic Press: New York, 1981. ISBN 0122349504.
- ^ Gajda, M.; Jancso, A. (2010). "Organotins, formation, use, speciation and toxicology". Metal ions in life sciences (Cambridge: RSC publishing). 7, Organometallics in environment and toxicology. ISBN 9781847551771.
- ^ S. Gómez-Ruiz et al. (2008). "Study of the cytotoxic activity of di and triphenyltin(IV) carboxylate complexes". Journal of Inorganic Biochemistry 102 (12): 2087–96. doi:10.1016/j.jinorgbio.2008.07.009. PMID 18760840.
- ^ Organic Syntheses, Coll. Vol. 4, p.881 (1963); Vol. 36, p.86 (1956). Link
- ^ C Gumy et al. (2008). "Dibutyltin Disrupts Glucocorticoid Receptor Function and Impairs Glucocorticoid-Induced Suppression of Cytokine Production". PLoS ONE 3: e3545. Bibcode:2008PLoSO...3.3545G. doi:10.1371/journal.pone.0003545.
External links
- National Pollutant Inventory Fact Sheet for organotins
- Industry information site
- Organotin chemistry in synthesis
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Health issues of plastics and Polyhalogenated compounds (PHCs)
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| Plasticizers: Phthalates |
- DIBP
- DBP
- BBP (BBzP)
- DIHP
- DEHP (DOP)
- DIDP
- DINP
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| Miscellaneous plasticizers |
- Organophosphates
- Adipates (DEHA
- DOA)
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| Monomers |
- Bisphenol A (BPA, in Polycarbonates)
- Vinyl chloride (in PVC)
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| Miscellaneous additives incl. PHCs |
- PBDEs
- PCBs
- Organotins
- PFCs
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| Health issues |
- Teratogen
- Carcinogen
- Endocrine disruptor
- Diabetes
- Obesity
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| Miscellanea |
- PVC
- Plastic recycling
- Plastic bottle
- Vinyl chloride
- Dioxins
- Polystyrene
- Foam food container
- PTFE (Teflon)
- California Proposition 65
- List of environmental health hazards
- Persistent organic pollutant
- European REACH regulation
- Japan Toxic Substances Law
- Toxic Substances Control Act
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有機スズ化合物の合成法として以下のものが知られる<ref>Thoonen, S. H. L.; Deelman, B.-J.; van Koten, G. (2004). "Synthetic aspects of tetraorganotins and organotin(IV) halides". J. Organomet. Chem. 689: 2145?2157. テンプレート:doi. オンライン版</ref>。
4有機置換スズは非常に安定であり、毒性や生理活性も低い。殺生物剤としては作用しないが、代謝されると有毒な3有機置換スズになる。触媒を合成する際の前駆体として利用される。
1有機置換スズは殺生物剤としての活性を持たない。哺乳類に対する毒性は非常に低い。メチルスズ、ブチルスズ、オクチルスズ、モノエステルスズはポリ塩化ビニルの熱安定化剤として用いられる。
