Electrospray Ionization Mass Spectrometry Studies of Rhenium(I) Bipyridyl Complexes

Abstract

Electrospray ionization mass spectrometry has been employed to study the formation of fragment ions from a series of rhenium(I) bipyridyl complexes [(4,4′-di-(COOEt)₂-bpy) Re(CO)₃XPyPF₆], where bpy is 2,2′-bipyridine, Py is pyridine and X is H, 4-methyl, 3-methyl, 4-hydroxyl, 3-hydroxyl, 4-amino, or 3-amino of the pyridine ligand. The effects of substituents (X) on the stability of the complexes has been investigated with the increase of fragmentor voltages. For different X substitutents, the stability of the complexes increases as X becomes more electron-donating from H to CH₃, OH and NH₂. For the same substitutent, the p-substituted pyridines have a stronger stabilizing effect than the corresponding m-substituted ones. Ligand exchange reaction was found in acetonitrile, where the pyridine ligand has been replaced by the solvent, indicated by the formation of [M–PF₆–XPy+MeCN]⁺ in the fragmentation.