Protactinium(V) chlorides

Abstract

Protactinium pentachloride is best prepared by reaction of low-fired or vacuum-dried pentoxide with thionyl chloride vapour at 375–425° or, mixed with carbon, with chlorine and carbon tetrachloride vapour at 400–500°. Diprotactinium(V) oxyoctachloride, Pa₂OCl₈, which occurs as a by-product of the latter reaction, is also obtained by heating the pentachloride with the stoicheiometric quantity of oxygen at 400°, It disproportionates above 270° in a vacuum, forming the pentachloride and the non-volatile diprotactinium(V) trioxytetrachloride, Pa₂O₃Cl₄, which in turn disproportionates above 520° in a vacuum to form PaCl₅ and protactinium(V) dioxymonochloride, PaO₂Cl. By varying the conditions, the reaction between PaCl₅ and oxygen can also be made to yield pure samples of diprotactinium(V) trioxytetrachloride, and an unstable oxytrichloride, PaOCl₃, has also been observed. Some chemical properties, X-ray diffraction studies, and infrared spectra are reported for these compounds.