Heterolysis of NH-Indoles by Bifunctional Amido Complexes and Applications to Carboxylation with Carbon Dioxide

Bifunctional amidoiridium complexes bearing C–N chelate ligands readily deprotonate unprotected NH-indole to give new κ1-N-indolyl­(amine) complexes, quantitatively. The resulting complexes were fully characterized by NMR, elemental analysis, and X-ray crystallography. The analogous Rh and Ru complexes were also synthesized by treatment of the precursory amine complexes with free indole in the presence of an equimolar amount of KOtBu. The indolyl moiety bound to the Ir center exhibits nucleophilic character to react with benzoyl chloride and to give 1- and 3-acylated indoles in yields of 68% and 18%, respectively. A related amido-Ru complex derived from an N-sulfonylated 1,2-diphenyl­ethylene­diamine ligand promoted carboxylation of indoles with CO2 under basic conditions to give indole-1-carboxylic acids.