One-Electron Oxidation Chemistry and Subsequent Reactivity of Diiron Imido Complexes

The chemical oxidation and subsequent
group transfer activity of
the unusual diiron imido complexes Fe­(iPrNP­Ph2)3FeNR (R = tert-butyl (tBu), 1; adamantyl, 2) was examined. Bulk chemical oxidation of 1 and 2 with Fc­[PF6] (Fc = ferrocene) is accompanied
by fluoride ion
abstraction from PF6– by the iron center trans to the FeNR functionality, forming F–Fe­(iPrNP­Ph2)3FeNR
(iPr = isopropyl) (R = tBu, 3; adamantyl, 4). Axial halide
ligation in 3 and 4 significantly disrupts
the Fe–Fe interaction in these complexes, as is evident by
the >0.3 Å increase in the intermetallic distance in 3 and 4 compared to 1 and 2. Mössbauer spectroscopy suggests that each of the
two pseudotetrahedral
iron centers in 3 and 4 is best described
as FeIII and that one-electron oxidation has occurred at
the tris­(amido)-ligated iron center. The absence of electron delocalization
across the Fe–FeNR chain in 3 and 4 allows these complexes to readily react with CO and tBuNC to generate the FeIIIFeI complexes F–Fe­(iPrNP­Ph2)3Fe­(CO)2 (5) and F–Fe­(iPrNPPh2)3­Fe­(tBuNC)2 (6), respectively.
Computational methods are utilized to better understand the electronic
structure and reactivity of oxidized complexes 3 and 4.