Cerium(IV) Ammonium Nitrate

Abstract

Cerium(IV) ammonium nitrate (CAN) is one of the most important reagent, which is used as one-electron oxidant and Lewis acid catalyst among the Lanthanide(IV) complexes in organic synthesis. 1 The reason for its general acceptance as a one-electron oxidant and Lewis acid is due to its large reduction potential valve of +1.61 V vs NHE (Normal Hydrogen Electrode) and low affinity for oxygen as compared to other Lewis acids. 2 CAN has been found chemically superior in many respects to widely employed manganese triacetate for the generation of radicals. 3 CAN has the additional advantages of having a low toxicity besides being inexpensive, reasonably soluble in many organic media, air stable, easily handled and allowing for a considerable degree of experimental simplicity. A large number of research papers and several reviews have been published for CAN mediated reactions. [4][5][6][7][8][9][10][11][12][13] Cerium has a property, unique among the lanthanides, which explain its ability to participate in one-electron transfer reactions, its ability to exist in two stable adjacent oxidation states +3 and +4. Cerium in its ground state has an electronic configuration of [Xe]4f 2 6s 2 , where Xe represents the xenon configuration. The electronic configuration of the Ce +3 ion is [Xe]4f 1 , while that of Ce +4 ion is [Xe]4f 0 .The enhanced stability of the vacant f shell in Ce +4 accounts for the ability of cerium to exist in the +4 oxidation state. The large reduction potential value of 1.61V (vs NHE) makes Ce(IV) a very efficient oxidizing reagents compared to other metal ions. Cerium(IV) ammonium nitrate is used as a catalyst for several types of transformations. They are classified into the following categories:1.Reactions involving the formation of carbon-carbon bond. 2.Reactions involving the formation of carbon-heteroatom bond.3. Miscellaneous transformations.