Stable N-bridged diiron (IV) phthalocyanine cation radical complexes: synthesis and properties

Oxidation of N-bridged diiron tetra-tert-butylphthalocyanine (FePc^tBu)₂N with ^tBuOOH in halogenated solvents afforded μ-nitrido diiron (IV) phthalocyanine cation radical complexes, (X)PcFe^IV–N–Fe^IVPc⁺˙(X) (X = Cl, Br), as evidenced by UV-vis, electron paramagnetic resonance (EPR), electrospray ionization mass spectrometry (ESI-MS), Mössbauer, X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) data. Continuous introduction ESI-MS showed the initial formation of the t-butylperoxo diiron complex ^tBuOO-(FePc^tBu)₂N followed by intermediate formation of a monohalogenated adduct which gave the dihalogenated complex as final stable product. Fe K-edge EXAFS analysis of (X)PcFe^IV–N–Fe^IVPc⁺˙(X) showed bridging N atom at a distance of 1.69(1) Å. The distance between two equivalent hexacoordinated in-plane iron (IV) centers is 3.39(1) Å. Fe–X bond lengths are 2.33 and 2.54 Å for X = Cl and Br, respectively. The use of (Cl)PcFe^IV–N–Fe^IVPc⁺˙(Cl) for the catalytic oxidation of organic substrates has been shown for the first time.