A Stable Homoleptic Organometallic Iron(IV) Complex
Om Prakash, Pavel Chábera, Nils W. Rosemann, Ping Huang, Lennart Häggström, Tore Ericsson, Daniel Strand, Petter Persson, Jesper Bendix, Reiner Lomoth, Kenneth Wärnmark
Abstract
Abstract 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.