Abstract
The chemical oxidation and subsequent
group transfer activity of
the unusual diiron imido complexes Fe(iPrNPPh2)3FeNR (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 FeNR functionality, forming F–Fe(iPrNPPh2)3FeNR
(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–FeNR 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.