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.