Abstract
Herein, we investigate the effects of ligand design on the nuclearity and reactivity of metal-ligand multiply bonded (MLMB) complexes to access an exclusively bimetallic reaction pathway for C-H bond functionalization. To this end, the diiron alkoxide [Fe(2)((Ph)Dbf)(2)] (1) was treated with 3,5-bis(trifluoromethyl)phenyl azide to access the diiron imido complex [Fe(2)((Ph)Dbf)(2)(μ-NC(8)H(3)F(6))] (2a) that promotes hydrogen atom abstraction (HAA) from a variety of C-H and O-H bond containing substrates. A diiron bis(amide) complex [Fe(2)((Ph)Dbf)(2)(μ-NHC(8)H(3)F(6))(NHC(8)H(3)F(6))] (3) was generated, prompting the isolation of the analogous bridging amide terminal alkoxide [Fe(2)((Ph)Dbf)(2)(μ-NHC(8)H(3)F(6))(OC(19)H(15))] (4) and the asymmetric pyridine-bound diiron imido [Fe(2)((Ph)Dbf)(2)(μ-NC(8)H(3)F(6))(NC(5)H(5))] (6a). We found that 6a is competent for toluene amination, indicating the effect of Lewis base-enhanced C-H bond functionalization. Mechanistic investigations suggest that the bimetallic bridging imido complex is the reactive intermediate as no monometallic species is detected during the time course of the reaction.