A square-planar di-N-carboxamido, dithiolato–cobalt(III) complex related to nitrile hydratase metallic site. Addition of axial ligands and EXAFS study of the derived dicyano and diisocyanido complexes

A square-planar cobalt(III) complex with a N2S2 di-N-carboxamido di-thiolato tetradentate ligand, mimics the metal core of the cobalt containing nitrile hydratases. It forms hexacoordinated complexes only upon addition of ligands like cyanide or isocyanides. An EXAFS analysis confirmed that two axial ligands get bound, and lead to a significant increase of the bond lengths between the cobalt(III) and the equatorial ligands. Whereas the planar complex is stable in the presence of air or hydrogen peroxide, its hexacoordinated derivatives with strong σ-donor axial ligands undergo an oxygenation of the equatorial thiolate ligands.