Analysis of oxovanadium(IV) complexes using electrospray mass spectrometry: Molecular ion formed by loss of an electron, and its product ions trapping oxygen.

Abstract

In addition to their biological properties, oxovanadium complexes have been widely applied as catalysts because of their excellent catalytic-oxidation capability. Recently, monometallic oxovanadium(IV) complexes have been used as catalysts in the electrophilic trifluoromethylation of silyl ketene imines. The study of catalysts can contribute to an understanding of the reaction mechanism. Six monometallic oxovanadium(IV) complexes were analyzed by electrospray ionization time-of flight mass spectrometry (ESI-TOFMS), and collision-induced dissociation mass spectrometry (CID-MS) experiments were conducted for selected cations [M]+ of oxovanadium(IV) complexes as well as a deuterium-labeled complex. Different collision gases were used to understand the source of the O2 and H2 O engaged in the gas-phase ion-molecule reaction. The oxovanadium(IV) complexes formed [M]+ ions by loss of an electron, with [M+14]+ ions being formed from [M]+ by loss of H2 O and addition of O2 . The fragmentation pathways of the [M]+ cations were further studied by ESI-MS/MS, and several ions produced by gas-phase ion-molecule reactions were detected and characterized, including vanadium-oxo, -peroxo and derivatives. Several unexpected ions were detected, including [M]+ , [M+14]+ and ions produced from gas-phase ion-molecule reactions. The study has contributed to the understanding of the structure and character of oxovanadium(IV) complexes, and it could facilitate the design of new oxovanadium catalysts and an understanding of their reaction mechanism.