1-Halobenzotriazoles as new halogenating agents for metal β-diketonates

Summary

1-Chloro- and 1-bromobenzotriazole were tested as new electrophilic halogenating agents for γ-substitution of acetylacetonates. The inert and less labile acetylacetonates, such as those containing Cr^III, Co^III, Al^III, Fe^III and VO^IV, underwent γ-halogenation leaving all the chelate rings intact, whereas the labile chelates of Cu^II, Ni^II, Co^II and Zn^II, apart from undergoing γ-halogenation, experienced partial ligand substitution by the benzotriazole moiety to yield a solid dimer, [M(BTA)(Xacac)]₂ (X = Cl or Br). Such selective formation of a mixed-ligand complex or γ-halo β-diketonate can be ascribed to the lability of the substrate chelate and to the strong coordinating ability of benzotriazole.