Cerium(III) Methanesulfonate1


[77998-20-0]  · C3H9CeO9S3  · Cerium(III) Methanesulfonate  · (MW 425.42) (.2H2O)

[73640-09-2]  · C3H13CeO11S3  · Cerium(III) Methanesulfonate  · (MW 461.46)

(stable, soluble cerium(III) salt used as a mediator for organic oxidation)

Alternate Name: cerous methanesulfonate.

Physical Data: white crystalline solid.

Solubility: very sol water, aqueous methanesulfonic acid, and aqueous acetonitrile; sol methanol; insol acetone.

Preparative Methods: prepared by the reaction of methanesulfonic acid with an aqueous suspension of cerium(III) carbonate. Solids can be precipitated with acetone or a large excess of methanesulfonic acid.

Handling, Storage, and Precautions: best used in aqueous solution as prepared. Cerium(III) salts are generally believed to be of low toxicity.

Electrochemical Oxidation.

The methanesulfonate salt of cerium is a convenient mediator for these oxidations because of its high solubility, the stability of the mesylate anion to electrochemical and cerium(IV) oxidation, and the very limited reactivity of the anion with oxidized products or intermediates.2 Cerium(IV) Trifluoromethanesulfonate also works well but is more expensive. A solution of cerium(III) methanesulfonate in aqueous methanesulfonic acid is oxidized to cerium(IV) at a platinum, RuO2/Ti, IrO2/Ti, or PbO2/Ti anode.3 Generally, protons are reduced to hydrogen at the cathode, which is isolated by a perfluorinated ion exchange membrane. Useful reductions can also be performed at the cathode, such as the reductive coupling of formaldehyde to ethylene glycol.4

Oxidations which have been performed with cerium(IV) methanesulfonate in aqueous methanesulfonic acid include the oxidation of alkylaromatics to ketones or aldehydes,2 polycyclic aromatics to quinones,2,5 and alkenes to carboxylic acids.6 The organic substrate is generally employed as a second phase, either as a pure liquid or dissolved in an inert solvent such as 1,2-dichloroethane.2 This improves selectivity and aids in product separation. The aqueous CeIV solution can then be regenerated electrochemically. The oxidation of 4-fluorotoluene to 4-fluorobenzaldehyde was performed directly at the anode with cerium trifluoromethanesulfonate as the mediator.7

It is sometimes beneficial to modify the oxidizing solution so as to contain an organic cosolvent and/or comediators (catalysts). Thus the oxidation of highly reactive substrates such as 4-methoxytoluene to 4-methoxybenzaldehyde was best accomplished with acetonitrile as a cosolvent.2 Also, the cerium(IV) oxidation of cyclododecene to dodecanedioic acid was performed with Ruthenium(VIII) Oxide6 and the oxidation of 2-methylnaphthalene to 2-methyl-1,4-naphthoquinone was performed with CrVI as comediator.2

A solid cerium(IV) material, Ce(MeSO3)2(OH)2, can be conveniently prepared by electrochemical oxidation of CeIII in dilute aq. MeSO3H. This solid can be used directly or redissolved in water for organic oxidations.2

1. Zinner, L. B. An. Assoc. Bras. Quim. 1979, 30, 27.
2. Kreh, R. P.; Spotnitz, R. M.; Lundquist J. T. JOC 1989, 54, 1526.
3. Spotnitz, R. M.; Kreh R. P.; Lundquist, J. T.; Press, P. J. J. Appl. Electrochem., 1990, 20, 209.
4. Weinberg, N. L.; Genders, J. D.; Mazur, D. J. U.S. Patent 4 950 368, 1990.
5. Moran, E. F. U.S. Patent 4 945 183, 1990.
6. Davis, D. D.; Sullivan, D. L. U.S. Patent 5 026 461, 1991.
7. Sasabe, M.; Yoshida, N.; Kumai, S.; Morimoto, T. Jpn. Patent 03 240 983, 1991.

Robert P. Kreh

W. R. Grace & Co., Columbia, MD, USA

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