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

Abstract

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 M(III)-corrole(3-) description for the simple Ag corroles and a noninnocent M(II)-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.

Ligand Noninnocence in Silver Corroles: A XANES Investigation

“…The intensity and total area (21 units) also decrease. These observations indicate a decrease in the valence Ag 4d‐hole character in 2‐Br 8 , which in turn is consistent with significant Ag II ‐corrole · 2– character …”

“…To sum up, Ag L 3 ‐edge XANES has provided direct experimental support for ligand noninnocence in the silver corrole 2‐Br 8 and thereby also for the unique electronic–structural switch described above . The present study is the first to apply XANES to probe the issue of ligand noninnocence in metallocorroles.…”

“…Simple silver triarylcorroles are also mildly saddled, but less so than analogous copper corroles. [5c], , In contrast, the first crystal structure of a silver β‐octabromo‐ meso ‐triarylcorrole revealed a strongly saddled macrocycle, with the degree of saddling essentially matching that observed for copper β‐octabromo‐ meso ‐triarylcorroles . Our tentative conclusion thus was that the silver octabromocorrole presumably had the same type of noninnocent electronic structure as its copper analogue.…”

Electronic Structure of Copper Corroles

“…Our electronic structure formulations are consistent with those proposed by Ghosh on the basis of computational studies. [29] As ar esult, the reversible one electron reduction and oxidation are both ligand-based. It has been previously demonstrated that both of these processes are dependent on the identity of the meso substituents.The half-wave potential of the reduction shifts 160 mV,w hile that of the oxidation shifts 240 mV upon varying the substituent at the 4-position of the meso aryl ring from methoxy to trifluoromethyl.…”

Synthesis and Molecular Structure of 99Tc Corroles

“…[20] Over severalr ecent studies, we have shown that the last two characteristics are typical of an innocent corrole 3À ligand,s uch as that found in Au, OsN, and ReO corroles, as opposed to an on-innocent corroleC 2À ligand, for which copper [20] and iron [21,22] corroles provide some of the best studied examples. [20] Over severalr ecent studies, we have shown that the last two characteristics are typical of an innocent corrole 3À ligand,s uch as that found in Au, OsN, and ReO corroles, as opposed to an on-innocent corroleC 2À ligand, for which copper [20] and iron [21,22] corroles provide some of the best studied examples.…”