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-thiolat o tetradentate ligand, mimics the metal core of the cobalt containing nitri le hydratases. It forms hexacoordinated complexes only upon addition of lig ands like cyanide or isocyanides. An EXAFS analysis confirmed that two axia l ligands get bound, and lead to a significant increase of the bond lengths between the cobalt(III) and the equatorial ligands. Whereas the planar com plex is stable in the presence of air or hydrogen peroxide, its hexacoordin ated derivatives with strong sigma -donor axial ligands undergo an oxygenat ion of the equatorial thiolate ligands. (C) 2001 Elsevier Science B.V. All rights reserved.