Dissociation behavior of Cu(urea)+ complexes generated by electrospray ionization

Electrospray ionization of aqueous solutions of Cu(II) salts in the presence of urea is used to generate the monoligated copper(I) cation Cu(urea)(+). To this end, the cone voltage is appropriately adjusted, thereby affording extensive collision-induced fragmentations of the multiply ligated ions evolving from solution. Among the wide range of transition-metal complexes studied during the two last decades, the dissociation behavior of Cu(urea)(+) is exceptional, because the product distributions significantly deviate from expectation based on thermochemical criteria only. While fully confirming previous experimental and theoretical studies of Luna et al. [J. Phys. Chem. A 104 (2000) 3132], the present results add a note of caution to the uncritical application of kinetic methods to the competitive dissociation of transition-metal complexes.