Lead(IV) acetate

Organometallic compound (Pb(C2H3O2)4)

Chemical compound

Lead(IV) acetate or lead tetraacetate is an metalorganic compound with chemical formula Pb(C₂H₃O₂)₄. It is a colorless solid that is soluble in nonpolar, organic solvents, indicating that it is not a salt. It is degraded by moisture and is typically stored with additional acetic acid. The compound is used in organic synthesis.^[2]

Structure

In the solid state the lead(IV) centers are coordinated by four acetate ions, which are bidentate, each coordinating via two oxygen atoms. The lead atom is 8 coordinate and the O atoms form a flattened trigonal dodecahedron.^[3]

Preparation

It is typically prepared by treating of red lead with acetic acid and acetic anhydride (Ac₂O), which absorbs water. The net reaction is shown:^[4][5]

Pb₃O₄ + 4 Ac₂O → Pb(OAc)₄ + 2 Pb(OAc)₂

The remaining lead(II) acetate can be partially oxidized to the tetraacetate by Cl₂, with a PbCl₂ by-product:

2 Pb(OAc)₂ + Cl₂ → Pb(OAc)₄ + PbCl₂

Reagent in organic chemistry

Lead tetraacetate is a strong oxidizing agent,^[6] a source of acetyloxy groups, and a general reagent for the preparation of organolead compounds. Some of its many uses in organic chemistry:

• Acetoxylation of benzylic, allylic,^[7] and α-oxygen ether C−H bonds, for example the conversion of dioxane to 2-acetoxy-1,4-dioxane ^[8]
• An alternative reagent to bromine in Hofmann rearrangement^[9]
• Dehydrogenation of hydrazones and hydrazines, for example that of hexafluoroacetone hydrazone to bis(trifluoromethyl)diazomethane^[10][11]
• Cleavage of α-hydroxy acids^[12] or 1,2-diols to their corresponding aldehydes or ketones, often replacing ozonolysis; for instance, the oxidation of di-n-butyl D-tartrate to n-butyl glyoxylate.^[13]
• Reaction with alkenes to form γ-lactones
• Oxidation of alcohols carrying a δ-proton to cyclic ethers.^[14]
• Oxidative cleavage of certain allyl alcohols in conjunction with ozone:^[15][16]
• Transformation of 1,2-dicarboxylic acids or cyclic anhydrides to alkenes

oxidative cleavage of allyl alcohols

• Conversion of acetophenones to phenyl acetic acids^[17]
• Decarboxylation of carboxylic acids to alkyl halides in the Kochi reaction^[18]

Safety

Lead(IV) acetate is toxic. It is a neurotoxin. It affects the gum tissue, central nervous system, kidneys, blood, and reproductive system.

References

1. "Substance Information - ECHA". echa.europa.eu.
2. Mihailo Lj. Mihailović; Živorad Čeković; Brian M. Mathes (2005). "Lead(IV) Acetate". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rl006.pub2. ISBN 978-0-471-93623-7.
3. Schürmann, M.; Huber, F. (1994). "A redetermination of lead(IV) acetate". Acta Crystallographica Section C. 50 (11): 1710–1713. doi:10.1107/S0108270194006438. ISSN 0108-2701.
4. J. C. Bailar, Jr. (1939). "Lead Tetracetate". Inorganic Syntheses. Inorganic Syntheses. Vol. 1. pp. 47–49. doi:10.1002/9780470132326.ch17. ISBN 978-0-470-13232-6.
5. M. Baudler (1963). "Lead(IV) Acetate". In G. Brauer (ed.). Handbook of Preparative Inorganic Chemistry, 2nd Ed. Vol. 2. NY,NY: Academic Press. p. 767.
6. J. Zýka (1966). "Analytical study of the basic properties of lead tetraacetate as oxidizing agent" (PDF). Pure and Applied Chemistry. 13 (4): 569–581. doi:10.1351/pac196613040569. S2CID 96821219. Retrieved 19 December 2013.
7. "(1R,5R)-(+)-Verbenone of High Optical Purity". Organic Syntheses. 72: 57. 1995. doi:10.15227/orgsyn.072.0057.
8. Organic Syntheses, Vol. 82, p.99 (2005) Article.
9. Baumgarten, Henry; Smith, Howard; Staklis, Andris (1975). "Reactions of amines. XVIII. Oxidative rearrangement of amides with lead tetraacetate". The Journal of Organic Chemistry. 40 (24): 3554–3561. doi:10.1021/jo00912a019.
10. Middleton, W. J.; Gale, D. M. (1970). "Bis(Trifluoromethyl)Diazomethane". Organic Syntheses. 50: 6. doi:10.15227/orgsyn.050.0006.
11. Robert K. Muller, Renato Joos, Dorothee Felix, Jakob Schreiber, Claude Wintner, and A. Eschenmoser (1976). "Preparation of N-Aminoaziridines: trans-1-Amino-2,3-diphenylaziridine, 1-Amino-2-phenylaziridine, and 1-Amino-2-phenylaziridinium Acetate". Organic Syntheses. 55: 114. doi:10.15227/orgsyn.055.0114.{{cite journal}}: CS1 maint: multiple names: authors list (link)
12. Ōeda, Haruomi (1934). "Oxidation of some α-hydroxy-acids with lead tetraacetate". Bulletin of the Chemical Society of Japan. 9 (1): 8–14. doi:10.1246/bcsj.9.8.
13. Organic Syntheses, Coll. Vol. 4, p.124 (1963); Vol. 35, p.18 (1955) Article.
14. M B Smith, J March. March's Advanced Organic Chemistry (Wiley, 2001) (ISBN 0-471-58589-0)
15. Álvarez Manzaneda, E. J.; Chahboun, R.; Cano, M. J.; Cabrera Torres, E.; Álvarez, E.; Álvarez Manzaneda, R.; Haidour, A.; Ramos López, J. M. (2006). "O₃/Pb(OAc)₄: a new and efficient system for the oxidative cleavage of allyl alcohols". Tetrahedron Letters. 47 (37): 6619–6622. doi:10.1016/j.tetlet.2006.07.020.
16. Conversion of 1-allylcyclohexanol to cyclohexanone, in the proposed reaction mechanism the allyl group is first converted to a trioxalane according to conventional ozonolysis which then interacts with the alkoxy lead group.
17. Myrboh, B.; Ila, H.; Junjappa, H. (1981). "One-Step Synthesis of Methyl Arylacetates from Acetophenones Using Lead(IV) Acetate". Synthesis. 2 (2): 126–127. doi:10.1055/s-1981-29358.
18. Jay K. Kochi (1965). "A New Method for Halodecarboxylation of Acids Using Lead(IV) Acetate". J. Am. Chem. Soc. 87 (11): 2500–02. doi:10.1021/ja01089a041.