Scaffold Dependent Coordination Modes of Chelating PEP‐Type Ligands in Iron(0) Carbonyl Complexes (E = O, S)

The reaction of iron pentacarbonyl with various chelating diphosphine ligands containing oxygen or sulfur atoms in their backbone, that can offer a potential third binding site, yields complexes that exhibit noteworthy coordination behavior. The resulting complexes are characterized by IR‐ and NMR spectroscopy, as well as highresolution mass spectrometry and elemental analysis. Depending on the natural P–P‐bite‐angle and flexibility of the ligands as well as the binding strength of the central heteroatom, different coordination geometries are observed. Eventually, we show that ligands with large bite angles favor the formation of binuclear complexes, whereas small bite angles lead to mononuclear complexes. Rather flexible ligands facilitate the formation of dimers. IR spectroscopy is employed to illuminate the coordination mode in solution and to provide insights into the donor properties of the utilized ligands.