Carbonyl dibromide: a novel reagent for the synthesis of metal bromides and bromide oxides

Abstract

Carbonyl dibromide reacted with a wide selection of d- and f-block transition-metal oxides to form either the metal bromide or bromide oxide; the reactions are driven by the elimination of carbon dioxide. In a typical reaction the metal oxide was treated with an eight-fold excess of COBr ₂ in a sealed Carius tube at 125 °C for 10 d (to ensure complete reaction of the metal oxide). As COBr ₂ and the reaction by-products (CO ₂ , CO and Br ₂ ) are all volatile, the desired products were obtained in essentially quantitative yield and a high degree of purity. Under these conditions V ₂ O ₅ , MoO ₂ , Re ₂ O ₇ , Sm ₂ O ₃ and UO ₃ were converted into VOBr ₂ , MoO ₂ Br ₂ , ReOBr ₄ , SmBr ₃ and UOBr ₃ , respectively. This route offers great potential for the preparation of many known bromide derivatives of the transition metals, lanthanides and actinides, in a very convenient manner, and also for the synthesis of new materials. A modified synthesis of carbonyl dibromide was elaborated, and its ¹⁷ O NMR and electron impact mass spectra are reported for the first time.