A Stable Homoleptic Organometallic Iron(IV) Complex

A homoleptic organometallic Fe(IV) complex that is stable in both solution and in the solid state at ambient conditions has been synthesized and isolated as [Fe(phtmeimb)(2)](PF(6))(2) (phtmeimb=[phenyl(tris(3‐methylimidazolin‐2‐ylidene))borate](−)). This Fe(IV) N‐heterocyclic carbene (NHC) complex was characterized by (1)H NMR, HR‐MS, elemental analysis, scXRD analysis, electrochemistry, Mößbauer spectroscopy, and magnetic susceptibility. The two latter techniques unequivocally demonstrate that [Fe(phtmeimb)(2)](PF(6))(2) is a triplet Fe(IV) low‐spin S=1 complex in the ground state, in agreement with quantum chemical calculations. The electronic absorption spectrum of [Fe(phtmeimb)(2)](PF(6))(2) in acetonitrile shows an intense absorption band in the red and near IR, due to LMCT (ligand‐to‐metal charge transfer) excitation. For the first time the excited state dynamics of a Fe(IV) complex was studied and revealed a ≈0.8 ps lifetime of the (3)LMCT excited state of [Fe(phtmeimb)(2)](PF(6))(2) in acetonitrile.