The effect of different modes of the carboxylato ligands on the reactivity of gaseous zinc acetate complexes is reported. Using infrared multiphoton dissociation spectroscopy, it is demonstrated that the coordination of acetate in [Imi)(n)Zn(CH3COO)](+) complexes (Imi = imidazole, n = 1-3) changes from bi- to monodentate upon coordination of the third imidazole ligand. This so-called carboxylate shift substantially influences the reactivity of the zinc acetate complexes in comparison to complexes with monodentate counterions. The differences in reactivities are demonstrated on the ligand exchange reactions of [LnZnX](+) (n = 2 or 3,; L = imidazole or pyridine; X = OH, Cl, CH3COO, and CH3CONHO).