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Organotin chemistry

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Organotin chemistry

Organotin compounds are those with tin linked to hydrocarbons.

Organotin compounds or stannanes are 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

  • Structure of organotin compounds 1
    • Organic derivatives of tin(IV) 1.1
      • Organotin halides and hydrides 1.1.1
      • Organotin oxides and hydroxides 1.1.2
      • Hypercoordinated stannanes 1.1.3
      • Triorganotin cations 1.1.4
    • Tin radicals (organic derivatives of tin(III)) 1.2
    • Organic derivatives of tin(II) 1.3
    • Organic derivatives of tin(I) 1.4
  • Preparation of organotin compounds 2
  • Reactions of organotin compounds 3
  • Applications 4
    • Biological applications 4.1
  • Toxicity 5
  • See also 6
  • References 7
  • External links 8

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 stannane (SnH4), is an unstable colourless gas.

Organotin oxides and hydroxides

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 acaricide Cyhexatin (also called Plictran), (C6H11)3SnOH. Such triorganotin hydroxides exist in equilibrium with the distannoxanes:

2 R3SnOH \overrightarrow{\leftarrow} 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+.

Idealized structure of trimeric diorganotin oxide.
Ball-and-stick model for (t-Bu2SnO)3.
Structure of diorganotin oxide, highlighting the extensive intermolecular bonding.

Hypercoordinated stannanes

Unlike carbon(IV) analogues but somewhat like silicon compounds, tin(IV) can also be 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 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

  • National Pollutant Inventory Fact Sheet for organotins
  • Industry information site
  • Organotin chemistry in synthesis

External links

  1. ^ a b c d e f Davies, Alwyn George. (2004) Organotin Chemistry, 2nd Edition Weinheim: Wiley-VCH. ISBN 978-3-527-31023-4
  2. ^ Gielen, Marcel (1973). "From kinetics to the synthesis of chiral tetraorganotin compounds". Acc. Chem. Res. 6: 198–202.  
  3. ^ 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
  4. ^ Reich, Hans J.; Phillips, Nancy H. (1986). "Lithium-Metalloid Exchange Reactions. Observation of Lithium Pentaalkyl/aryl Tin Ate Complexes".  
  5. ^ 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".  
  6. ^ Masaichi Saito, Sanae Imaizumi, Tomoyuki Tajima, Kazuya Ishimura, and Shigeru Nagase (2007). "Synthesis and Structure of Pentaorganostannate Having Five Carbon Substituents".  
  7. ^  
  8. ^ 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
  9. ^ Holleman, A. F.; Wiberg, E. (2001), Inorganic Chemistry, San Diego: Academic Press,  
  10. ^ Lawrence R. Sita "Heavy-Metal Organic Chemistry: Building with Tin" Acc. Chem. Res., 1994, volume 27, pp 191–197. doi:10.1021/ar00043a002
  11. ^ Philip P. Power "Bonding and Reactivity of Heavier Group 14 Element Alkyne Analogues" Organometallics 2007, volume 26, pp 4362–4372. doi:10.1021/om700365p
  12. ^ Sander H.L. Thoonen, Berth-Jan Deelman, Gerard van Koten (2004). "Synthetic aspects of tetraorganotins and organotin(IV) halides" (PDF).  
  13. ^ G. J. M. Van Der Kerk, J. G. A. Luijten "Tetraethyltin" Org. Synth. 1956, volume 36, page 86ff. doi:10.15227/orgsyn.036.0086
  14. ^ Dietmar Seyferth "Di-n-butyldivinyltin" Org. Synth. 1959, volume 39, page 10. doi:10.15227/orgsyn.039.0010
  15. ^ "Organometallic Syntheses: Nontransition-Metal Compounds" John Eisch, Ed. Academic Press: New York, 1981. ISBN 0122349504.
  16. ^ 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.  
  17. ^ 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.  
  18. ^ Organic Syntheses, Coll. Vol. 4, p.881 (1963); Vol. 36, p.86 (1956). Link
  19. ^ C Gumy; et al. (2008). "Dibutyltin Disrupts Glucocorticoid Receptor Function and Impairs Glucocorticoid-Induced Suppression of Cytokine Production". PLoS ONE 3: e3545.  

References

Chemical bonds to carbon
Core organic chemistry Many uses in chemistry
Academic research, but no widespread use Bond unknown
CH He
CLi CBe CB CC CN CO CF Ne
CNa CMg CAl CSi CP CS CCl CAr
CK CCa CSc CTi CV CCr CMn CFe CCo CNi CCu CZn CGa CGe CAs CSe CBr CKr
CRb CSr CY CZr CNb CMo CTc CRu CRh CPd CAg CCd CIn CSn CSb CTe CI CXe
CCs CBa CHf CTa CW CRe COs CIr CPt CAu CHg CTl CPb CBi CPo CAt Rn
Fr CRa Rf Db CSg Bh Hs Mt Ds Rg Cn Uut Fl Uup Lv Uus Uuo
CLa CCe CPr CNd CPm CSm CEu CGd CTb CDy CHo CEr CTm CYb CLu
Ac CTh CPa CU CNp CPu CAm CCm CBk CCf CEs Fm Md No Lr

See also

Tetraorgano-, diorgano-, and monoorganotin compounds generally exhibit low toxicity and low biological activity. DBT may however be immunotoxic.[19]

Triorganotin compounds can be highly toxic. Tri-n-alkyltins are bactericides and fungicides. Reflecting their high bioactivity, "tributyltins" were once used in marine anti-fouling paint.[1]

Toxicity

Organotin complexes have been studied in anticancer therapy.[17]

Tributyltin compounds were once widely used as marine anti-International Maritime Organization.

"miticides and acaricides. Tributyltin oxide has been extensively used as a wood preservative.[1][1]

Biological applications

n-Butyltin trichloride is used in the production of tin dioxide layers on glass bottles by chemical vapor deposition.

An organotin compound is commercially applied as stabilizers in dibutyltin dilaurate, are used as catalysts for the formation of polyurethanes, for vulcanization of silicones, and transesterification.[1]

Applications

and radical chemistry (e.g. radical cyclizations, Barton–McCombie deoxygenation, Barton decarboxylation, etc.).

Stille reaction scheme

Important reactions, discussed above, usually focus on organotin halides and Stille reaction is considered important. It entails coupling reaction with sp2-hybridized organic halides catalyzed by palladium:

Reactions of organotin compounds

The alkyl sodium compounds with tin halides yields tetraorganotin compounds.

Bu2SnCl2 + 1/2 LiAlH4 → Bu2SnH2 + 1/2 LiAlCl4"

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 + 2 C2H3MgBr → Bu2Sn(C2H3)2 + 2 MgBrCl

The mixed organo-halo tin compounds can be converted to the mixed organic derivatives, as illustrated by the synthesis of dibutyldivinyltin:[14]

A related method involves redistribution of tin halides with organoaluminium compounds.

3 R4Sn + SnCl4 → 4 R3SnCl
R4Sn + SnCl4 → 2 R2SnCl2
R4Sn + 3 SnCl4 → 4 RSnCl3

The symmetrical tetraorganotin compounds can then be converted to various mixed chlorides by redistribution reactions (also known as the "Kocheshkov comproportionation"):

4 EtMgBr + SnCl4 → Et4Sn + 4 MgClBr

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]

Preparation of organotin compounds

Structure of an Ar10Sn10 "prismane", a compound containing Sn(I) (Ar = 2,6-diethylphenyl).

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]

Organic derivatives of tin(I)

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.

2 R2Sn \overrightarrow{\leftarrow} (R2Sn)2

In principle divalent tin compounds might be expected to form analogues of alkenes with a formal 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]

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.

Organic derivatives of tin(II)

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]

Tin radicals (organic derivatives of tin(III))

[7]

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