Protonation Reactions of Dinuclear Pyrazolato Iridium(I) Complexes

The complex [{Ir((mu)-Pz)(CNBut)2}2] (1) undergoes double protonation reactions with HCl and with HO2CCF3 to give the neutral dihydride complexes [{Ir((mu)-Pz)(H)(X)(CNBut)2}2] (X = Cl, (eta)1-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((mu)-Pz)(H)(Cl)(CNBut)2}2] evolves in solution to the cationic complex [{Ir((mu)-Pz)(H)(CNBut)2}2((mu)-Cl)]Cl. Removal of the anionic chloride by reaction with methyltriflate allows the isolation of the triflate salt [{Ir((mu)-Pz)(H)(CNBut)2}2((mu)-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((mu)-Pz)(Cl)(CNBut)2}2((mu)-Cl)]OTf. Protonation of both metal centers in [{Ir((mu)-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((mu)-Pz)(CO)(P{OPh}3)}2] reacts with HCl and with HO2CCF3 to give the neutral Ir(III)/Ir(III) complexes [{Ir((mu)-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 ((mu)-Pz)2Ir(H)(CO)(P{OPh}3)] and the mixed-valence Ir(I)/Ir(III) complex [(P{OPh}3)(CO)Ir((mu)-Pz)2Ir(H)((eta)1-O2CCF3)(CO)(P{OPh} 3)].