STUDY OF FORMATION AND FRAGMENTATION OF IONIC COMPLEXES OF POLYDENTATE LIGANDS WITH AL(III) AND GLYCEROL BY FAST-ATOM-BOMBARDMENT MASS-SPECTROMETRY .1. POLYDENTATE LIGANDS

The complexation reactions of aluminum ions with polydentate ligands s uch as 12-crown-4, 15-crown-5, 18-crown-6, 1,10-dithia-18-crown-6, dic yclohexyl-18-crown-6, dibenzo-18-crown-6, and dibenzo-24-crown-8 and a cyclic analogs mono-, di-, tri-, tetra-, penta-, and hexaethylene glyc ols were studied using FAB mass spectrometry. These cyclic ligands for m (M + 117)(+), (M + 157)(+), (M + 231)(+), and (M + 253)(+) ions with different aluminum-containing species. Collisionally activated dissoc iations of these adduct ions gave fragment ions, initially due to the loss of ligands directly attached to aluminum, followed by insertion o f aluminum into the remaining ligand skeleton. Further fragmentation o f the metal-containing species gave ions corresponding to consecutive losses of C2H4O units. Fragmentations of deuterium-labelled ions were used to help in establishing fragmentation pathways. Selectivity towar ds metal chelation is observed in this order: 12-crown-4 < 15-crown-5 < 18-crown-6. The elemental compositions of adduct ions were confirmed by high-resolution measurements. The formation of (M + Al - 2H)(+) io n, obtained by the displacement of two hydroxy protons, is more favore d for tetra- and pentaethylene glycols.