Synthesis and Stabilization of a Monomeric Iron(II) Hydroxo Complex via <i>Intra</i>molecular Hydrogen Bonding in the Secondary Coordination Sphere

Utilizing the pyridinediimine ligand [(2,6-iPrC6H3)NCMe)(N(iPr)2C2H4)NCMe)C5H3N] (didpa), the iron(II) complexes Fe(didpa)Br2 (1), [Fe(Hdidpa)Br2][PF6] (2), and [Fe(Hdidpa)CH3CN(OH)][2PF6] (3) were synthesized and characterized by X-ray diffraction and spectroscopic methods. The X-ray data show that the didpa scaffold is capable of forming intramolecular hydrogen bonds in the solid state located within the secondary coordination sphere of complexes 2 and 3. These hydrogen bonds are responsible for stabilizing the iron(II) hydroxo ligand in 3, which originates from H2O.