Gas-Phase Chemistry of Arylimido-Functionalized Hexamolybdates [Mo6O19]2-

The gas-phase fragmentations of a series of arylimido derivatives of hexamolybdate [Mo6O18(NC6H5-n R (n) )](2-) (2-10, where R = CH3, i-C3H7, OCH3, NO2; n = 1 or 2) versus the parent species [Mo6O19](2-) (1) were systematically studied using electrospray tandem mass spectrometry (ESI). Fragmentation of 1 generates two molybdate fragments only, [Mo3O10](2-) and [Mo4O13](2-), whereas decomposition of 2-10 went through two dissociation pathways in which path A generates a variety of molybdate fragments via breaking the Mo-N bond followed by the cleavages of the multiple Mo-O bonds, whereas path B produces a range of molybdate fragments with arylimido group via breaking the multiple Mo-O bonds on POM framework. Moreover, the presences of mixed-oxidation-state molybdate fragments are characteristic for the fragmentation. The gas-phase stability order obtained by energy-variable collision-induced dissociation (CID) experiment reveals that 2-10 are generally less stable than 1 and substitution on the benzene ring exerts a considerable effect on the stabilization of the hybrid clusters.