Iron Pincer Complexes with a Pyrrole-Based PNP Ligand: Synthesis and Reactivity

The development of homogeneous transition metal catalysts containing iron is desired due to iron’s relatively high natural abundance and low toxicity compared to noble metals, such as platinum, ruthenium, and iridium. Many iron catalysts contain pincer ligands which help to stabilize the metal center and tune its reactivity. To further explore this area, iron complexes containing a pyrrole-based PNP ligand, PNpyrP (PNpyrP = 2,5-bis((di-iso-propylphosphino)methyl)pyrrolide), were synthesized. Deprotonation of the pro-ligand, (PNpyrP)H, with a base followed by transmetallation with an iron (II) precursor gave the desired PNpyrP-iron complexes. Both coordinatively unsaturated, paramagnetic and coordinatively saturated, diamagnetic complexes were isolated. These compounds were then characterized by multinuclear NMR spectroscopy and X-ray crystallography. Finally, the reactivity of the complexes towards hydrogen gas, ligand substitution, and hydride reagents was investigated.