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)](PF6)(2)(phtmeimb=[phenyl(tris(3-methylimidazolin-2-ylidene))borate](-)). This (FeN)-N-IV-heterocyclic carbene (NHC) complex was characterized by(1)H NMR, HR-MS, elemental analysis, scXRD analysis, electrochemistry, Mossbauer spectroscopy, and magnetic susceptibility. The two latter techniques unequivocally demonstrate that [Fe(phtmeimb)(2)](PF6)(2)is a triplet Fe(IV)low-spinS=1 complex in the ground state, in agreement with quantum chemical calculations. The electronic absorption spectrum of [Fe(phtmeimb)(2)](PF6)(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 approximate to 0.8 ps lifetime of the(3)LMCT excited state of [Fe(phtmeimb)(2)](PF6)(2)in acetonitrile.