Bis-picket-fence corroles

Superstructured corrole ligands related to the picket-fence porphyrins were obtained from (2,6-dichlorophenyl)dipyrromethane in two steps. Condensation with an aryl aldehyde followed by oxidative ring closure yields A2B corroles with four peripheral bromine atoms. Palladium-catalyzed fourfold amidation at these positions results in the formation of the desired sterically encumbered species, accompanied mainly by disubstituted by-products. The insertion of iron ions into the blocked cavity of the new corrole ligands proves successful when directed towards the nitrosyl derivative. The X-ray crystallographic investigation of such an iron complex allows a detailed view of the steric restraints imposed by the bulky amido substituents.

Palladium-catalyzed amidation is the key to sterically hindered and chiral triarylcorrole ligands. The steric encumbrance found in these species does not interfere with metal insertion but seems sufficient to direct a potential substrate. Metal chelates of such ligands therefore show much promise as bioinorganic models and stereoselective catalysts.Figure optionsDownload as PowerPoint slide