Nonheme Mononuclear and Dinuclear Iron(II) and Iron(III)\nFluoride Complexes and Their Fluorine Radical Transfer Reactivity

The\nnonheme iron(II) complexes containing a fluoride anion, Fe<sup>II</sup>(BNPA<sup>Ph2</sup>O)(F) (<b>1</b>) and [Fe<sup>II</sup>(BNPA<sup>Ph2</sup>OH)(F)(THF)](BF<sub>4</sub>) (<b>2</b>),\nwere synthesized and structurally characterized. Addition of dioxygen\nto either <b>1</b> or <b>2</b> led to the formation of\na fluoride-bridged, dinuclear iron(III) complex [Fe<sub>2</sub><sup>III</sup>(BNPA<sup>Ph2</sup>O)<sub>2</sub>(F)<sub>2</sub>(μ-F)]<sup>+</sup> (<b>4</b>), which was characterized by single-crystal\nX-ray diffraction, <sup>1</sup>H NMR, and elemental analysis. An iron(II)(iodide)\ncomplex, Fe<sup>II</sup>(BNPA<sup>Ph2</sup>O)(I) (<b>3</b>),\nwas prepared and reacted with O<sub>2</sub> to give the mononuclear\ncomplex <i>cis</i>-Fe<sup>III</sup>(BNPA<sup>Ph2</sup>O)(OH)(I)\n(<b>5</b>). Addition of excess fluoride to <b>5</b> led\nto the formation of the oxo-bridged, dinuclear iron(III) complex [Fe<sub>2</sub><sup>III</sup>(BNPA<sup>Ph2</sup>O)<sub>2</sub>(F)<sub>2</sub>(μ-O)] (<b>6</b>), while the mononuclear iron(III)(fluoride)\ncomplex <i>cis</i>-Fe<sup>III</sup>(BNPA<sup>Ph2</sup>O)(F)(Cl)\n(<b>7</b>) was prepared from the addition of excess F<sup>–</sup> to Fe<sup>III</sup>(BNPA<sup>Ph2</sup>O)Cl<sub>2</sub>. The dinuclear\ncomplexes <b>4</b> and <b>6</b> were unreactive to fluorine\nradical transfer, but mononuclear <b>7</b> reacts with the radical\nsubstrate (<i>p</i>-MeO-C<sub>6</sub>H<sub>4</sub>)<sub>3</sub>C<sup>•</sup> to give the fluorine radical transfer\nproducts Fe<sup>II</sup>(BNPA<sup>Ph2</sup>O)(Cl) and (<i>p</i>-OMe-C<sub>6</sub>H<sub>4</sub>)<sub>3</sub>CF. These results show\nthat a mononuclear Fe<sup>III</sup>(F) complex is capable of mediating\nfluorine radical transfer, even in the presence of second coordination\nsphere hydrogen bonds to the F<sup>–</sup> ligand. These findings\nare placed in context with what is known about the nonheme iron halogenases\nand related synthetic catalysts regarding their ability, or lack thereof,\nto mediate fluorine radical transfer reactions.