Protonation reactions of dinuclear pyrazolato iridium(I) complexes

The complex [{Ir(μ-Pz)(CNBut)2}2] (1) undergoes double protonation reactions with HCl and with HO2CCF3 to give the neutral dihydride complexes [{Ir(μ-Pz)(H)(X)(CNBut)2}2] (X = Cl, η1-O2CCF3), 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(μ-Pz)(H)(Cl)(CNBut)2}2] evolves in solution to the cationic complex [{Ir(μ-Pz)(H)(CNBut)2}2(μ-Cl)]Cl. Removal of the anionic chloride by reaction with methyltriflate allows the isolation of the triflate salt [{Ir(μ-Pz)(H)(CNBut)2}2(μ-Cl)]OTf. This complex undergoes a metathesis reaction of hydride by chloride in CDCl3 under exposure to the direct sunlight to give the complex [{Ir(μ-Pz)(Cl)(CNBut)2}2(μ-Cl)]OTf. Protonation of both metal centers in [{Ir(μ-Pz)(CO)2}2] with HCl occurs at low temperature, but eventually the mononuclear compound [IrCl(HPz)(CO)2] is isolated. The related complex [{Ir(μ-Pz)(CO)(P{OPh}3)}2] reacts with HCl and with HO2CCF3 to give the neutral Ir(III)/Ir(III) complexes [{Ir(μ-Pz)(H)(X)(CO)(P{OPh}3)}2], 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 [(P{OPh}3)(CO)(Cl)Ir(μ-Pz)2Ir(H)(CO)(P{OPh}3)] and the mixed-valence Ir(I)/Ir(III) complex [(P{OPh}3)(CO)Ir(μ-Pz)2Ir(H)(η1-O2CCF3)(CO)(P{OPh}3)].The generous financial support from MCyT(DGI)/FEDER (Project BQU2002-00074) is gratefully acknowledged.Peer reviewe