Formation of [Cu(CO2)(CH3OH)]+ and [Cu(N2)(CH3OH)]+ by gas-phase dissociation and exchange reactions

• Published in: International journal of mass spectrometry 2019-02, Vol.436, p.1-6
• Main Authors: Metzler, Luke J., Koehler, Stephen, Somogyi, Árpád, Van Stipdonk, Michael J.
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Copper ion; Electrospray ionization; Ion trap mass spectrometry; Ion-molecule reactions; Metal ion complexes
• ISSN: 1387-3806; 1873-2798
• DOI: 10.1016/j.ijms.2018.10.030

[Display omitted] •Cationic Cu(II)-acetate complexes undergo demethylation in the gas phase.•Upon demethylation, the Cu(II) is reduced to Cu(I) which binds the remaining neutral CO2.•The Cu(I)−CO2 complex undergoes spontaneous ligand exchange with neutral N2 and H2O. Electrospray ionization and multiple-stage tandem mass spectrometry were used to study the collision-induced dissociation of methanol-coordinated copper-acetate cations, and the ion-molecule reactions of specific product ions. Our experiments led to the discovery of unusual gas-phase ions with compositions such as [Cu(CO2)(CH3OH)]+ and [Cu(N2)(CH3OH)]+. The latter is generated by spontaneous exchange of CO2 for N2 in an ion-molecule reaction. Isotopic labeling studies and high mass-resolution measurements provide data to support the product ion composition assignments. Density functional theory calculations corroborate the experimental observations, both with respect to the preferential decarboxylation over methanol ligand elimination, and the spontaneous nature of the ion-molecule reactions.