Protactinium tetrabromide

Protactinium pentabromide is appreciably more stable than uranium pentabromide, which decomposes to the tetrabromide at 160°C (116). It is moisture-sensitive and hydrolyzes rapidly on the addition of water. The few known complexes are discussed later. 

Like other actinide tetrahalides, protactinium tetrachloride and tetrabromide form stable complexes with phosphine oxides (48, 55) and iV jAT -dimethylacetamide (24), but the tetrachloride-dimethyl sulfoxide... 

The actinide tetrachloride-DMA complexes cover quite a range of stoichiometry (22,24,27) and the behavior of protactinium tetrachloride is intermediate between that observed for thorium and uranium tetrachloride (Table XI). PaCl4 2.5 DMA is isostructural with the y-modifica-tion of the other 1 2.5 complexes and with PaBr4 2.5 DMA (24). However, the uranium tetrabromide complex, UBi 4 2.5 DMA, possesses a different structure. The 1 5 tetrabromide-DMA complexes (Th to U inclusive) are isostructural (24). 

Even fewer complexes with nitrogen donor ligands have been reported and all are methyl cyanide adducts (Tables X and XI). Protactinium pentabromide forms a soluble 1 3 complex in contrast to the 1 1 complexes formed by niobium and tantalum pentahalides (46). Other actinide pentahalide-methyl cyanide complexes are still unknown. Protactinium tetrachloride, tetrabromide, and tetraiodide react with anhydrous, oxygen-free methyl cyanide to form slightly soluble 1 4 complexes (44, 48) which are isostructural with their actinide tetrahalide analogs. 

Tetrachloride and tetrabromide complexes are known for thorium, protactinium, uranium, neptunium, and plutonium. These are similarly produced by halide-based oxidation of metals or hydrides, or by halogenation of oxides. A common structural type is reported for most compounds. The reported structure of thorium tetrachloride reveals that the coordination geometry about the metal is dodecahedral.The compounds are generally volatile and can be sublimed. The gas-phase electron diffraction structure of suggests that the molecule is... 

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