Acidolyis and oxygen atom transfer reactivity of a diiridium hydroperoxo complex

Oxygenation of Ir(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)Cl(3)H (1, tfepma = CH(3)N[P(OCH(2)CF(3))(2)](2)) furnishes Ir(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)Cl(3)(OOH) (2), the first isolable iridium hydroperoxo complex. This complex transfers an oxygen atom to triphenylphosphine, producing triphenylphosphine oxide and Ir(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)Cl(3)(OH) (3) in high yield. Reaction of 2 with acid induces cleavage of the O-O bond, initially forming [Ir(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)Cl(3)(OH(2))]Cl (4), which was identified by NMR spectroscopy. With HCl as the acid source, the chloride anion displaces water to form the pseudo-C(2h) isomer of Ir(2)(II,II)(tfepma)(2)(CN(t)Bu)(2)Cl(4) (5). With 2,6-lutidinium chloride as the acid, complex 4 forms initially and is deprotonated by the conjugate base to afford 3 as the major product.