Chemistry of Protactinium

Since the chemistry of actinium is confined to the Ac + ion, it can readily be separated from thorium (and the lanthanides, for that matter) by processes like solvent extraction with thenoyltrifluoroacetone (TTFA) and by cation-exchange chromatography. The latter is an excellent means of purification, as the Ac + ion is much more strongly bound by the resin than its decay products. 

Many of the complexes of Pa that have been studied are halide complexes, falling into two types anionic species with all-halide coordination, and neutral Lewis base adducts, usually of the chloride PaCU. 

Historically, the fluoride complexes are most important. Aristid Von Grosse (1934) used K2PaF7 in his determination of the atomic mass of Pa in 1931. Colourless crystals of this and other complexes MPaFe, M2PaFv, and MsPaFg (M = K, Rb, Cs) can be obtained by changing the stoichiometry, e.g.  

This complex has tricapped trigonal prismatic nine coordination of Pa, whilst MPaFe has dodecahedral 8 coordination and NasPaFg the very rare cubic 8 coordination. Other halide complexes can be made by appropriate methods  

Six-coordinate [PaXe] ions have been confirmed by X-ray diffraction for (Me4N)2PaXe (X = Cl, Br) and Cs2PaCl6. 

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Some recent preparative chemistry of protactinium. D. Brown, Adv. Inorg. Chem. Radiochem., 1969, 12, 1-51 (138). 

Some Recent Preparative Chemistry of Protactinium D. Brou n... 

First identified in 1913 (the first compound, Pa20s, was isolated in 1927 by von Grosse, who isolated the element in 1931), protactinium is not generally extracted. Most of what is known about the chemistry of protactinium ultimately results from the extraction in 1960 by the UK Atomic Energy Authority of some 125 grams of Pa, from 60 tons of waste material left over from the extraction of uranium, at a cost of about 500,000 (very roughly, 1,250,000 at today s exchange rate). 

E. S. Palshin, B. F. Myasoedov, Analytical Chemistry of Protactinium, Ann Arbor-Humphrey, Ann Arbor, 1970. 

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