Ligand Noninnocence in Coinage Metal Corroles: A Silver Knife-Edge

A silver β‐octabromo‐meso‐triarylcorrole has been found to exhibit a strongly saddled geometry, providing the first instance of a strongly saddled corrole complex involving a metal other than copper. The Soret maxima of the Ag octabromocorroles also redshift markedly in response to increasingly electron‐donating para substituents on the meso‐aryl groups. In both these respects, the Ag octabromocorroles differ from simple Ag triarylcorrole derivatives, which exhibit only mild saddling and substituent‐insensitive Soret maxima. These results have been rationalized in terms of an innocent MIII‐corrole3− description for the simple Ag corroles and a noninnocent MII‐corrole.2− description for the Ag octabromocorroles. In contrast, all copper corroles are thought to be noninnocent, while all gold corroles are innocent. Uniquely among metallocorroles, silver corroles thus seem poised on a knife‐edge, so to speak, between innocent and noninnocent electronic structures and may tip either way, depending on the exact nature of the corrole ligand. A study of ligand noninnocence in coinage metal corroles, including both simple meso‐triarylcorroles and β‐octabromo‐meso‐triarylcorroles is presented. Earlier findings that copper corroles are noninnocent and gold corroles are innocent stand unchanged, whereas silver corroles are seemingly poised on a knife‐edge between innocent and noninnocent behavior (see graphic).