Transition-metal Complexes of Pyrrole Pigments. XVII. Preparation and Spectroscopic Properties of Corrole Complexes

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Abstract
Nickel(II), copper(II), and cobalt(III) complexes were prepared with corroles; 2,3,7,8,12,13,17,18-octaethylcorrole (OEC), 2,3,17,18-tetramethyl-7,8,12,13-tetraethylcorrole (MEC), and 8,12-bis[2-(ethoxycarbonyl)ethyl]2,3,7,13,17,18-hexamethylcorrole (PMC). For the coordination with nickel and copper ions, the corroles acted as dianionic ligands to yield electrically neutral complexes. These complexes exhibited metalloporphyrin-like electronic spectra, while they showed spectra which bear a much closer resemblance to those for metalloporphyrins as the anionic complexes were formed upon addition of alkali. The corroles coordinate to tervalent cobalt as trianionic ligands to form neutral complexes, which were reduced to the corresponding cobalt(II) complexes with sodium hydroborate. These reduced species gave a unique set of g-values (g1>>g2>g3) for the complexes of macrocyclic ligands with conjugated double bond system. The plausible coordination geometry as well as the structural properties of the corrole ligands has been discussed.