A mass spectrometric study of halogenated beryllium μ4-oxohexa-μ-acetates

The electron impact mass spectra of Be₄O(CHal₃CO₂)₆ (Hal = F, Cl) are reported. The compounds give two series of fragment ions, Be₄OL_x]⁺ and Be₄OL₊]⁺, where L is an intact ligand or its fragmentation product. The major ligand dissociation path is the elimination of CHal₂CO₂ with halogen transfer to the metal. Other processes of importance are the loss of acid anhydride fragments, CF₂ with fluorine shift to the carboxyl group carbon atom, and halogens. Trinuclear ions also undergo decarboxylation, e.g. to give Be₂O(CHal₃CO₂)₂(CHal₃)]⁺. Both spectra contain comparatively intense peaks of double-charged ions. The fragmentation patterns are rationalized by stereochemical considerations.