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( i PrNP­Ph2)3FeNR (R = tert-butyl ( t Bu), 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( i PrNP­Ph2)3FeNR ( i Pr = isopropyl) (R = t Bu, 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 t BuNC to generate the FeIIIFeI complexes F–Fe( i PrNP­Ph2)3Fe(CO)2 (5) and F–Fe( i PrNPPh2)3­Fe( t BuNC)2 (6), respectively. Computational methods are utilized to better understand the electronic structure and reactivity of oxidized complexes 3 and 4.