THE REACTIONS OF CU2-4) AND CU2+(CH3CN)(3)(H2O) AT LOW COLLISION ENERGY WITH NEUTRAL MOLECULES IN A TRIPLE SECTOR QUADRUPOLE INSTRUMENT((CH3CN)(N) (N = 2)

Cu2+(CH3CN)(n) (n = 2-4) and Cu2+(CH3CN)(3)(H2O) have been formed by e lectrospray ionization of solutions of CuSO4 in aqueous acetonitrile, The ions have been identified by CAD and their reactivates have been i nvestigated by ion-molecule reactions with acetonitrile-d(3), acetone and acetone-d(6), ammonia and benzene and benzene-d(6) at low collisio n energy in the central collision cell of a quadrupole/hexapole/quadru pole instrument. Ammonia is the least reactive molecule with all the i ons. The degree to which Cu(TI) is reduced to Cu(I) depends on its deg ree of ligation and also on the collision gas. CD3CN exchanges for CH3 CN with the tetra and tri-ligated ions with no charge reduction, while little charge conservation occurs in reaction with Cu2+(CH3CN)(2). Si milarly, acetone exchanges for CH3CN in the tetracoordinated ions but reacts almost exclusively by charge reduction with the less ligated io ns. Both CD3CN and acetone can react with the tetracoordinated ions to form Cu(II) ions with up to six ligands, but although the tetracoordi nated products have partially to fully exchanged ligand shells, the pe nta-and hexacoordinated products have ligands exclusively from the col lision gas. This is attributed to the way in which the ions traverse t he hexapole collision cell. Ammonia reacts by charge reduction, CH3CN replacement and addition, Benzene reacts with all ions solely by charg e reduction, the benzene cation being a prominent product. The presenc e of H2O rather than CH3CN as a ligand leads to enhanced reactivity. I n general, susceptibility to charge reduction decreases with the numbe r of CH3CN ligands on the precursor ion. (C) 1998 Elsevier Science B.V . All rights reserved.