Selective C-H Bond Cleavage with a High-Spin Fe IV -Oxido Complex.

Non-heme Fe monooxygenases activate C-H bonds using intermediates with high-spin Fe IV -oxido centers. To mimic these sites, a new tripodal ligand [pop] 3- was prepared that contains three phosphoryl amido groups that are capable of stabilizing metal centers in high oxidation states. The ligand was used to generate [Fe IV pop(O)] - , a new Fe IV -oxido complex with an S = 2 spin ground state. Spectroscopic measurements, which included low-temperature absorption and electron paramagnetic resonance spectroscopy, supported the assignment of a high-spin Fe IV center. The complex showed reactivity with benzyl alcohol as the external substrate but not with related compounds (e.g., ethyl benzene and benzyl methyl ether), suggesting the possibility that hydrogen bonding interaction(s) between the substrate and [Fe IV pop(O)] - was necessary for reactivity. These results exemplify the potential role of the secondary coordination sphere in metal-mediated processes.