Abstract
The bis-(borane) o-{(C(6)F(5))(2)B}(2)C(6)F(4) (1) reacts with dioxygen in the presence of decamethylferrocene (FeCp*(2), Cp* = pentamethylcyclopentadienyl) to deliver the salt [(μ-OH)-o-{B-(C(6)F(5))(2)}(2)C(6)F(4)]-[FeCp*(2)] (2) featuring a hydroxide sequestered by the two adjacent boron atoms. Mechanistic investigations of this formal 4-electron reduction of O(2) suggest that it goes through the formation of a superoxide adduct [1-O(2)](-), which evolves through disproportionation into O(2) and a peroxo-adduct [1-O(2)](2-). Upon coordination of another equivalent of 1, the thus-generated 4-fold boron-sequestered peroxide {[1](2)-O(2)}(2-) undergoes homolytic O-O bond cleavage to yield a pair of oxyl radicals [1-O(•)](-). These highly reactive intermediates subsequently perform hydrogen atom abstraction to lead to the hydroxide salt 2. Our observations point to FeCp*(2) being the H atom purveyor in this final step.