Ligand displacement reactions of dimer and trimer pyridyl ligand transition metal complexes

Ligand exchange reactions of pyridyl ligand/transition metal complexes are examined in a quadrupole ion trap mass spectrometer to evaluate the ability of multidentate Ligands to displace other pyridyl ligands in complexes whe re the charge is highly delocalized and there is a great degree of ligand r epulsions. Partially or fully coordinated transition metal ions in dimer or trimer species involving small mono- or bidentate pyridyl ligands undergo ligand displacement reactions with larger bi- and tridentate pyridyl ligand s. Larger ligands with greater chelation abilities, such as 1,10-phenanthro line and 2,2':6,2 "-terpyridine, are often able to simultaneously displace two nonchelating ligands from a partially coordinated metal ion. However, t he analogous reactions involving displacement of bidentate chelating ligand s from more fully coordinated transition metal ion complexes are nearly que nched. In other cases, mixed-ligand dimer and trimer complexes are observed , indicating step-wise displacement of the initially complexed ligands. (C) 1999 Elsevier Science B.V.