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.