A Tetrapodal Penta-Carbene Ligand and Iron(III) Complex

Abstract

We report the first tetrapodal pentadentate ligand composed of five N-heterocyclic carbene donors. The proto-ligand [CC4H5Me](OTf)3 (3) is formed in good yields from commercially available reagents. Upon removal of 5 proton equivalents from 3 with bulky non-nucleophilic bases a dianionic penta-carbene framework is provided in good yields as a dilithium complex CC4MeLi2 (4). Addition of FeCl3 to a solution of 4 formed in situ provides CC4MeFeCl (5) in moderate yield. Solution-state magnetism measurements of 5 are consistent with a S=1/2 Fe(III) center. The related diamagnetic Fe(II) compound CC4MeFe (6) can be formed through reduction of 5 using KC8 though poor solubility characteristics have hampered its formation on a preparative scale and full characterization.