Protactinium oxytribromide

As mentioned above, protactinium(V) oxytribromide is invariably obtained as a by-product during the preparation of the pentabromide. It is also formed (32, 45) when stoichiometric amounts of the penfa-bromide and either oxygen [Eq. (6)] or antimony sesquioxide [Eq. (7)] are heated together in a sealed vessel at 350°C. Although it is found with... 

Protactinium(V) oxytribromide possesses monoclinic symmetry (Table III). The structure (53, 54) comprises chains of protactinium atoms linked by bridging bromine atoms and cross-linked by 3-coordinate oxygen atoms. Each protactinium atom is 7-coordinate (Pig. 5) and protactinium-bromine bond lengths lie within the range 2.69-3.02 A. It would be interesting to have structural information on the relatively unstable uranium(V) oxytribromide since the limited X-ray powder... 

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