Structural Diversity in Metal Complexes with a Dinucleating Ligand Containing Carboxyamidopyridyl Groups

The synthesis of a (carboxyamido)pyridinepyrazolate (H5bppap) dinucleating ligand is described. Bimetallic iron and cobalt complexes of H5bppap ([MII2H2bppap]+) showed structural differences in both their primary and secondary coordination spheres. The binding of small molecules into the preorganized ligand cavity is verified by the hydration of [FeII2H2bppap]+ and [CoII2H2bppap]+, leading to the formation of complexes [{CoII(OH)}CoIIH3bppap]+ and [{FeII(OH)}FeIIH3bppap]+, in which one of the metal centers has a terminal hydroxo ligand.