GAS-PHASE REACTIONS OF DOUBLY-CHARGED ALKALINE-EARTH AND TRANSITION-METAL COMPLEXES OF ACETONITRILE, PYRIDINE, AND METHANOL GENERATED BY ELECTROSPRAY-IONIZATION

Formation and low energy collision-induced dissociation (CID) of doubl y charged metal(II) complexes ([metal(II) + L-n](2+), metal(II) = Co(I I), Mn(II), Ca(II), Sr(II) and L = acetonitrile, pyridine, and methano l) were investigated. Complexes of [metal(II) + L-n](2+) where n less than or equal to 7 were obtained using electrospray ionization. Experi mental parameters controlling the dissociation pathways for [Co(II) (CH3CN)(2)](2+) were studied and a strong dependence of these processe s on the collision energy was found. However, the dissociation pathway s appear to be independent of the cone potential, indicating low inter nal energy of the precursor ions. In order to probe how these processe s are related to intrinsic parameters of the ligand such as ionization potential and metal ion coordination, low energy CID spectra of [meta l(II) + L-n](2+) for ligands such as acetonitrile, pyridine, and metha nol were compared. For L = pyridine, all metals including the alkaline earth metals Ca and Sr were reduced to the bare [metal(I)](+) species . Hydride transfer was detected upon low energy CID of [metal(II) + L- n](2+) for metal(II) Co(II) and Mn(II) and L = methanol, and corrobora ted by signals for [metal(II) + H-](+) and [metal(II) + H- + CH3OH](+) , as well as by the complementary ion [CH3O](+). (C) 1997 American Soc iety for Mass Spectrometry.