Organoantimony chemistry

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Organoantimony chemistry is the chemistry of compounds containing a carbon to antimony (Sb) chemical bond. Relevant oxidation states are SbV and SbIII. The toxicity of antimony [1] limits practical application in organic chemistry. [2]

Contents

Antimony(III) derivatives

Synthesis

These synthesis typically entail alkylation of Antimony trichloride reacts with organolithium or Grignard reagents: [3]

SbCl3 + 3 RLi (or RMgCl) → R3Sb

Triphenylstibine (triphenylantimony) is one of the best studied organoantimony compounds and representative of the entire class of stibines.

The cyclic compound stibole, a structural analog of pyrrole, has not been isolated, but substituted derivatives have. Antimony metallocenes are known as well:

14SbI3 + 3 (Cp*Al)4 → [Cp∗
2Sb]+[AlI4]− + 8Sb + 6 AlI3

The Cp*-Sb-Cp* angle is 154°.

Reactions

As soft Lewis donors, stibines form some coordination compounds. [4] : 348 . Stibines can be oxidized with halogens:

R3Sb + Br2 → R3SbBr2

The resulting dihalides, when heated, release the organic bromide: [5]

R3SbX2 → R2SbX + RX

Up treatment with metallic sodium, one C-Sb bond breaks: [4] : 443 

Ph3Sb + Na → Ph2SbNa + PhNa

Antimony(V) derivatives

Pentacoordinate antimony compounds are called stiboranes. They are synthesised from stibines and halogens (Ph = C6H5):

Ph3Sb + Cl2 → Ph3SbCl2

As confirmed by X-ray crystallography, dichlorostiboranes feature pentacoordinate Sb(V) with trans-diaxial chloride ligands. [6] The dichlorostiborane reacts with phenyl lithium to give pentaphenylantimony:

Ph3SbCl2 + 2 PhLi → Ph5Sb

Pentaphenylantimony decomposes at 200 °C to triphenylstibine and biphenyl.

Like the organobismuth compounds, stiboranes form onium compounds and ate complexes. Unsymmetrical stiboranes can also be obtained through the stibonium ions:

R5Sb + X2 → [R4Sb]+[X]− + RX
[R4Sb]+[X]− + R'MgX → R4R'Sb

In the related Me5Sb, proton NMR spectra recorded at -100 °C cannot resolve the two types of methyl protons. This observation is consistent with rapid Berry pseudorotation.

Antimony resists forming multiple bonds, as anticipated by the double bond rule. Thus, it forms C6H5)3Sb(OH)2, not C6H5)3SbO. This observation contrasts with the behavior of phosphorus compounds where C6H5)3P(OH)2 is not observed and C6H5)3PO is robust. [7] C6H5)3SbO is claimed to exist as a dimer. [5]

Distibines and antimony(I) compounds

Structure of (PhSb)6 PhSbhexamer.svg
Structure of (PhSb)6

Distibines are formally SbII compounds, but feature tricoordinate Sb atoms with a single Sb-Sb bond. They may have interest as thermochromes. For example, tetramethyl­distibine is colorless when gas, yellow when liquid, red when solid just below the melting point of 18.5 °C, shiny-blue when cooler, and again yellow at cryogenic temperatures. [9] [4] : 442  A typical synthesis first displaces an SbIII halide with an alkali metal and then reduces the resulting anion with ethylene dichloride. [4] : 781–783 

Like its lighter congener, arsenic, organoantimony compounds can be reduced to cyclic oligomers that are formally antimony(I) compounds. [4] : 563–577 

Compounds with multiple bonds to Sb

Stibabenzene Stibabenzene.svg
Stibabenzene

Stibabenzene, a planar ring akin to benzene, can be prepared by dehydrohalogenation of an stibacyclohexadiene. [10] Compounds have been made with the core structure C-Sb=Sb-C, the main requirement being that the organic substituent must be bulky. [11]

References

  1. ↑ Filella, M. (2010). "Alkyl derivatives of antimony in the environment". Metal Ions in Life Sciences. 7. Cambridge: RSC publishing: 267–301. doi:10.1039/9781849730822-00267. ISBN   978-1-84755-177-1. PMID   20877810.
  2. ↑ C. Elschenbroich, A. Salzer Organometallics : A Concise Introduction (2nd Ed) (1992) from Wiley-VCH: Weinheim. ISBN   3-527-28165-7
  3. ↑ Hiers, G. S. (1927). "Triphenylstibine". Organic Syntheses. 7: 80. doi:10.15227/orgsyn.007.0080.
  4. 1 2 3 4 5 Patai, Saul, ed. (1994). The Chemistry of Organic Arsenic, Antimony, and Bismuth Compounds. Chemistry of Functional Groups. Chichester, UK: Wiley. doi:10.1002/0470023473. ISBN   047193044X.
  5. 1 2 Grund, Sabina C.; Hanusch, Kunibert; Breunig, Hans J.; Wolf, Hans Uwe (2006). "Antimony and Antimony Compounds". Ullmann's Encyclopedia of Industrial Chemistry. doi:10.1002/14356007.a03_055.pub2. ISBN   978-3-527-30385-4.
  6. ↑ Begley, M. J.; Sowerby, D. B. (1993). "Structures of triphenylantimony(V) dibromide and dichloride". Acta Crystallographica Section C Crystal Structure Communications. 49 (6): 1044–1046. Bibcode:1993AcCrC..49.1044B. doi:10.1107/S0108270192011958.
  7. ↑ Pankaj, S.; Rosas, N.; Espinosa-Pérez, G.; Cabrera, A. (1996). "Triphenylstibine Dihydroxide". Acta Crystallographica Section C Crystal Structure Communications. 52 (4): 889–891. doi:10.1107/S0108270195013898.
  8. ↑ Breunig, Hans Joachim; Häberle, Karl; Dräger, Martin; Severengiz, Tevfik (1985). "(C6H5Sb)6·(1,4-dioxane), the First Cyclohexastibane". Angewandte Chemie International Edition in English. 24: 72–73. doi:10.1002/anie.198500721.
  9. ↑ Organoantimony compounds with element-element bonds H.J. Breunig, R. Rosler Coordination Chemistry Reviews 163 (1997) 33-53
  10. ↑ Ashe, Arthur J. (February 2016). "The Route to Phosphabenzene and Beyond" (PDF). European Journal of Inorganic Chemistry. 2016 (5): 572–574. doi:10.1002/ejic.201600007. hdl: 2027.42/117476 . ISSN   1434-1948. S2CID   101713336.
  11. ↑ Roller, Clara A.; Doler, Berenike; Steller, Beate G.; Saf, Robert; Fischer, Roland C. (2024). "A Distibene with Extremely Long Sb=Sb Distance and Related Heavier Dipnictenes from Salt-Free Metathesis Reactions". European Journal of Inorganic Chemistry. 27 (10) e202300586. doi:10.1002/ejic.202300586.
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