Anionic Trinuclear Iridium(I) Oxo Complex: Synthesis and Reactivity as a Metal-Centered σ-Donor Ligand to Gold(I) and Silver(I)

The diiridium(I) μ-hydroxo complex [Ir(μ-OH)(cod)]2 (1; cod = 1,5-cyclooctadiene) readily reacted with aqueous NaOH in DMSO-d6 or NaN(SiMe3)2 in THF to give the anionic trinuclear iridium oxo complex Na[{Ir(cod)}3(μ3-O)2] (2) in high yield. Complex 2 crystallized in the form of the contact ion pair [{Na(thf)2(H2O)}(μ4-O){Ir(cod)}3(μ3-O)] (2·(THF)2(H2O)) upon recrystallization from THF–hexane. Reactions of 2 with group 11 metal electrophiles (AuCl(PPh3), AgCl(PPh3), and AgCl) afforded iridium–gold and −silver mixed-metal cluster complexes [{Ir(cod)}3(μ3-O)2M(PPh3)] (3a: M = Au; 3b: M = Ag) and [Na(dmso)3(μ-dmso)]2[{Ir(cod)}3(μ3-O)2Ag(μ-Cl)]2 (4) containing Ir(I) → Au(I)/Ag(I) dative interactions as revealed by DFT and NBO analysis. These results demonstrate the ability of 2 to act as an iridium(I)-centered σ-donor ligands to the group 11 metal centers. Single-crystal X-ray structures of 2·(THF)2(H2O), 3a, 3b, and 4 are presented.