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Organothallium compounds are compounds that contain the carbon-thallium bond. It shows reminiscence to the chemistry of organogallium and organoindium compounds. There is a greater abundance of organothallium(III) compounds than that of organothallium(I) compounds.

Organothallium(I) Chemistry

The only stable organothallium(I) species are cyclopentadienyl complexes.[1]Attempts to make alkyl and aryl thallium(I) compounds from thallium(I) halides and Grignard reagents or organolithium reagents will result in immediate disproportionation, as in the preparation of trimethyl thallium from methyl lithium, methyl iodide, and thallium(I) iodide (the highly reactive thallium metal formed from disproportionation further reacts with methyl iodide to form monomethyl thallium which then disproportionates again). Thallium(I) cyclopentadienide adopts a zig-zag chain structure of cyclopentadienide and thallium.

The air-stable cyclopentadienyl thallium is made from TlOH and cyclopentadiene, and preparation of derivatives is also possible. Alkylcyclopentadienyl thallium compounds are air sensitive.[1]

Thallium cyclopentadienide can react as a cyclopentadienyl donor (as when reacting with metal halides)[1], or a cyclopentadienyl acceptor (as upon reaction with magnesocene).[2] The latter yields the bent dicyclopentadienyl thallium anion, analogous to that of stannocene.

Organothallium(III) Chemistry

Trialkyl Organothallium Compounds

Structure

In the gas and liquid phase, trialkyl organothallium compounds are monomeric and planar. In the solid phase, there is significant intermolecular interactions between the monomers.[2]

Preparation

Trialkyl thallium compounds, like those of indium and gallium, can be prepared from thallium trihalides and Grignard reagents or organolithium reagents, though the former may yield the ether complex of the product.[2] However, unlike that of gallium and indium, trialkyl thallium compounds cannot be prepared from dialkyl mercury and thallium trihalides, in which case R2TlX will be obtained.[2]Trimethyl thallium can be prepared from methyl iodide, methyl lithium, and thallium(I) iodide.[2]Triethyl thallium can be similarly prepared.

Reactions

Trialkyl thallium compounds can undergo alkyl exchange with itself and some acidic hydrocarbons like alkynes and cyclopentadiene. Some trialkyl thallium compounds are photosensitive.[1]

Dialkyl Organothallium Compounds

Structure

R2TlX has ionic properties, such that they are water soluble and that R2TlOH is strongly basic. The structure of the dialkyl thallium anion ressemble that of dialkyl mercury.[1][3][4]However, dimeric or polymeric structures may exist in inert solvents or crystalline structures.

Preparation

Dialkyl Organothallium Halides can be prepared from two equivalents of Grignard reagents and thallium trihalides, or the reaction of trialkylthallium compounds with protonic compounds.[1][4]Another preparation involves the oxidation of thallium metal with aryldiazonium tetrafluoroborate salts. They are formed from dialkyl mercury and thallium trihalides instead of trialkyl thallium compounds.

Reactions

Dialkyl Organothallium Compounds are mostly stable to air and moisture.[1] The halide atom can be substituted by nucleophiles, and the alkyl group can be abstracted by mercury acetate. (C5F6)2TlBr can act as alkyl donors for low-valent metal halides, performing oxidative alkyl insertions onto the metals with itself being reduced to thallium(I) bromide.

Monoalkyl Organothallium Compounds

Preparation

Arylthallium dichloride can be prepared from TlCl3 and aryl boronic acids.[5]Excess boronic acid will result in diarylthallium chloride formation. Thallium(III) trifluoroacetate can oxidize aromatic rings to form ArTl(OCOCF3)2.[6]Alkenes can also react with thallium(III) salts in a fashion analogous to oxymercuration to yield monoalkyl organothallium compounds.

Reactions

Phenylthallium dihalides are prone to eliminating halobenzene, with the tendency increasing from chlorine to iodine, to the point that the iodide derivative is unknown.[7]They are Lewis acidic in nature. Nucleophile treatment can displace the halide atom, and substituent self-exchange to form thallium(III) halides and diphenylthallium halides is also possible. The dichloride can undergo transmetallation with mercuric chloride.[7]

Applications

Cyclopentadienyl thallium can be used to make cyclopentadienyl complexes via cyclopentadienyl transfer to metal halides.

ArTl(OCOCF3)2 obtained from the oxidation of aromatic compounds by thallium(III) trifluoroacetate can be used to form a variety of aryl derivatives, as shown below, and has found applications in organic chemistry.[1]

History

The first organothallium compound, diethylthallium chloride, was prepared in 1870, shortly after the discovery of the element thallium.[8]

See also

References

  1. ^ a b c d e f g h 无机化学丛书 第二卷 [Books of Inorganic Chemistry]. pp. 524–528. ISBN 978-7-03-056380-4.
  2. ^ a b c d e Housecroft, Catherine (2018). Inorganic Chemistry (5th ed.). Pearson. pp. 887–892. ISBN 978-1-292-13414-7.
  3. ^ Housecroft, Catherine (2018). Inorganic Chemistry (5th ed.). Pearson. pp. 887–892. ISBN 978-1-292-13414-7.
  4. ^ a b Greenwood (2001). Chemistry of the Elements (2nd ed.). Elsevier. pp. 262–265. ISBN 0-7506-3365-4.
  5. ^ Challenger, Frederick; Richards, Oswald V. (1934). "94. Organo-derivatives of bismuth and thallium". Journal of the Chemical Society (Resumed): 405–411. doi:10.1039/jr9340000405. ISSN 0368-1769.
  6. ^ 无机化学丛书 第二卷 [Books of Inorganic Chemistry]. pp. 524–528. ISBN 978-7-03-056380-4.
  7. ^ a b Challenger, Frederick; Richards, Oswald V. (1934). "94. Organo-derivatives of bismuth and thallium". Journal of the Chemical Society (Resumed): 405–411. doi:10.1039/jr9340000405. ISSN 0368-1769.
  8. ^ Lee, A. G. (1970-01-01). "Organothallium chemistry". Quarterly Reviews, Chemical Society. 24 (2): 310–329. doi:10.1039/QR9702400310. ISSN 0009-2681.