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Several procedures for the demetalation of silver(III) corrolates have been tested. Acidic conditions induce removal of the silver ion but they can also promote concomitant oxidation of the corroie nucleus to an isocorrole species, the degree of which will depend upon the specific acidic media. This oxidation cannot be completely avoided by addition of hydrazine, particularly In the case of 3-NO 2 substituted complexes which are quantitatively converted into the corresponding 3-NO 2,5-hydroxy isocorroles upon sliver ion removal. Several β-nitro isocorrole products were Isolated, and one was structurally characterized. Electrochemical and chemical reductive methods for silver(III) corrolates demetalation were then tested with the aim to avoid the formation of isocorroles. While reaction with sodium borohydride was shown to be quite effective to demetalate unsubstituted sliver corrolates this was not the case for the β-nitro derivatives where the peripheral nitro group Is reduced by borohydride giving the corresponding 3-amino free base corroie species. For the β-nitro corroie silver complexes, a successful approach was obtained using DBU/THF solutions which afforded the 3-NO 2 corroie free-base compound as a single reaction product In good yield. These conditions were also effective for unsubstituted corroles although longer reaction times were necessary in this case. To study in greater detail the corroie demetalation behavior, selected Ag(III) derivatives were characterized by cyclic voltammetry in pyridine, and the demetalation products spectrally characterized after controlled potential reduction in a thin-layer spectroelectrochemical cell. © 2009 American Chemical Society.

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Inorganic Chemistry

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