Solvent displacement in transition metal complexes

Ligand exchange reactions of transition metal ions solvated by two acetone or two acetonitrile molecules with multidentate polyethers or pyridyl ligan ds are undertaken in a quadrupole ion trap mass spectrometer. The ability o f the polyether or pyridyl ligand to displace one or both solvent molecules is correlated with the number of binding atoms in the multidentate ligand, the flexibility of the ligand along with its ability to fully coordinate o r encapsulate the metal ion, and the strength of the solvent/metal bonds. T he smaller polyethers displace one solvent molecule, thus generating stable (M+ + polyether + solvent) complexes. The larger polyethers rapidly displa ce both solvent molecules, leading to formation of stable (M+ + polyether) complexes, because of the ability of the large polyethers to encapsulate or fully coordinate the metal ion. The pyridyl ligands tend to favor formatio n of (M+ + pyridyl ligand + solvent) mixed-ligand complexes, regardless of the number of nitrogen atoms or flexibility of the pyridyl ligand. The pyri dyl ligands are unable to fully encapsulate the metal ion, so one solvent m olecule may remain bound to the metal ion, (Int J Mass Spectrom 185/186/187 (1999) 49-59) (C) 1999 Elsevier Science B.V.