Abstract
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.
