Acidolyis and oxygen atom transfer reactivity of a diiridium hydroperoxo complex

Abstract

Oxygenation of Ir₂^II,II(tfepma)₂(CN^tBu)₂Cl₃H (1, tfepma = CH₃N[P(OCH₂CF₃)₂]₂) furnishes Ir₂^II,II(tfepma)₂(CN^tBu)₂Cl₃(OOH) (2), the first isolable iridium hydroperoxo complex. This complex transfers an oxygen atom to triphenylphosphine, producing triphenylphosphine oxide and Ir₂^II,II(tfepma)₂(CN^tBu)₂Cl₃(OH) (3) in high yield. Reaction of 2 with acid induces cleavage of the O–O bond, initially forming [Ir₂^II,II(tfepma)₂(CN^tBu)₂Cl₃(OH₂)]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 Ir₂^II,II(tfepma)₂(CN^tBu)₂Cl₄ (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.