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, Mosbauer 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.