Iron Complexes Supported by a Dual Dearomatized PNPN Ligand

Ligands containing a dearomatized ligand motif are often employed to stabilize transition metal complexes and may be employed in catalytic transformations. While complexes containing one dearomatized structural feature are common, dual dearomatized systems are seldom encountered. In this article, we describe the synthesis of various iron complexes based upon a macrocyclic PNPN ligand. Synthetic entry to the dual dearomatized ligand (PNPN*) can be achieved upon deprotonation of the Fe dibromide complex with base in the presence of π-acidic ligands. The electronic structure of these complexes was examined by NMR- and ⁵⁷Fe Mössbauer spectroscopy and computationally modeled. Reactivity studies regarding ligand substitution of the π-acidic ligands and protonation of the PNPN* scaffold are described.