Protactinium bromides

Sergey Serafimovich Berdonosov, Dr. Sci. was born in 1939 in Moscow, Russia. He was a gold medalist at school in 1956 and received an excellence diploma from Moscow State University in 1961. His PhD thesis, defended in 1964, was dedicated to zirconium, hafnium, niobium, tantalum, and protactinium bromides, and his Dr. Sci. thesis (2002) was devoted to the radiochemical studies of desublimation and new approaches to the determination of physicochemical properties of substances and materials. 

In the fall of 1934, Dr. Grosse reduced this pure oxide by two methods and obtained from it the metal protactinium, which is even rarer than radium, but much more permanent in air. In die first method, he bombarded the oxide on a copper target, in a high vacuum, with a stream of electrons. After a few hours, he obtained a shiny, partly sintered, metallic mass, stable in air. In his second method, he converted the oxide to the iodide (or chloride or bromide) and cracked it in a high vacuum on an electrically heated tungsten filament, according to the reaction ... 

Volatile protactinium pentaehloride has been prepared in a vacuum by reaction of the oxide with phosgene at 550° C or with carbon tetrachloride at 200°C. Reduction of this at 600°C with hydrogen leads to protactinium(IV) tetrachloride, Pad. which is isostructural with uranium(IV) tetrachloride, UCI4. The pentaehloride can be converted into the bromide or iodide by heating with the corresponding hydrogen halide or alkali halide... 

Niobium and tantalum(V) chlorides and tantalum(V) bro-midef yield the complexes MX6-CHSCN, and protactinium(V) bromide yields orange PaBr8 3CH8CN if the same procedure is used. 

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... 

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