A Low-Spin d^5 Iron Imide: Nitrene Capture by Low-Coordinate Iron(I) Provides the 4-Coordinate Fe(III) Complex [PhB(CH_2PPh_2)_3]FetN-p-tolyl

Abstract

Entry into “[PhBP_3]Fe” chemistry affords a rare, pseudotetrahedral iron(I) complex, [PhBP_3]Fe(PPh_3), with an S = 3/2 ground state. This precursor undergoes rapid oxidation by aryl azide to produce the d^5 imide [PhBP_3]Fe_≡NAr (Ar = p-tolyl). The Fe(III) imide is significant in that it is low-spin and represents the first mononuclear imide of iron. Doublet [PhBP_3]Fe_≡NAr reacts rapidly and quantitatively with CO at room temperature to release isocyanate and [PhBP_3]Fe(CO)_2. The [PhBP_3]Fe(CO)_2 byproduct is also a precursor to [PhBP_3]Fe_≡NAr upon addition of aryl azide.