The relative basicities of complexes of the type [IrX(CO)L2](X = Cl, Br, or I; L = tertiary phosphine or tertiary arsine) towards carboxylic acids

Abstract

Complexes of the type trans-[IrX(CO)L₂](X = Cl, Br, or I; L = tertiary phosphine or tertiary arsine) are protonated by carboxylic acids, probably to give iridium(III) complexes of type [IrHX(OOC·R)(CO)L₂]. For non-sterically hindered acids the greater the pK_a value of the acid the more complete the addition. The tendency of the iridium(I) complexes to become protonated by benzoic acid increases in the order X = Cl < Br < I, and L = PPh₃ < AsPh₃ < PMePh₂ < PEt₂Ph < PMe₂Ph < AsMe₂Ph < PMe₃. The electronic and steric factors responsible for these effects are discussed.