Protonation reactions of dinuclear pyrazolato iridium(I) complexes.

The complex [Ir(mu-Pz)(CNBu(t))(2)] (1) undergoes double protonation reactions with HCl and with HO(2)CCF(3) to give the neutral dihydride complexes [Ir(mu-Pz)(H)(X)(CNBu(t))(2)] (X = Cl, eta(1)-O(2)CCF(3)), in which the hydride ligands were located trans to the X groups and in the boat of the complexes, both in the solid state and in solution. The complex [Ir(mu-Pz)(H)(Cl)(CNBu(t))(2)] evolves in solution to the cationic complex [Ir(mu-Pz)(H)(CNBu(t))(2)(mu-Cl)]Cl. Removal of the anionic chloride by reaction with methyltriflate allows the isolation of the triflate salt [Ir(mu-Pz)(H)(CNBu(t))(2)(mu-Cl)]OTf. This complex undergoes a metathesis reaction of hydride by chloride in CDCl(3) under exposure to the direct sunlight to give the complex [Ir(mu-Pz)(Cl)(CNBu(t))(2)(mu-Cl)]OTf. Protonation of both metal centers in [Ir(mu-Pz)(CO)(2)] with HCl occurs at low temperature, but eventually the mononuclear compound [IrCl(HPz)(CO)(2)] is isolated. The related complex [Ir(mu-Pz)(CO)(POPh)] reacts with HCl and with HO(2)CCF(3) to give the neutral Ir(III)/Ir(III) complexes [Ir(mu-Pz)(H)(X)(CO)(POPh)], respectively. Both reactions were found to take place stepwise, allowing the isolation of the intermediate monohydrides. They are of different natures, i.e., the metal-metal-bonded Ir(II)/Ir(II) compound [(POPh)(CO)(Cl)Ir(mu-Pz)(2)Ir(H)(CO)(POPh)] and the mixed-valence Ir(I)/Ir(III) complex [(POPh)(CO)Ir(mu-Pz)(2)Ir(H)(eta(1)-O(2)CCF(3))(CO)(POPh)].