Effect of the carboxylate shift on the reactivity of zinc complexes in the gas phase.

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(CH(3)COO)](+) 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 [L(n)ZnX](+) (n = 2 or 3,; L = imidazole or pyridine; X = OH, Cl, CH(3)COO, and CH(3)CONHO).