Protactinium acetylacetonate

The acetylacetonate PajacacjgClg has been prepared by direct reaction between protactinium pentachloride and acetylacetone in methylene dichloride. The addition of isopentane to this reaction mixture results in the formation of long, bright yellow needles of the complex, and single crystal studies have shown these to possess monoclinic symmetry, space group P2i/c with do = 8.01, = 23.42, Cq = 18.63 A, and... 

In studying the complexation of protactinium(IV) with acetylacetone, Lundqvist (1974) indicated that in solution the metal ion was present as PaO " (or equally PafOH) )- However, Lundqvist also noted that this behaviour was not present in other tetravalent metal ions such as Zr(IV), Hf(IV) or other actinide(IV) ions. As shown in Section 9.2.3, protactinium(V) exists as PaO ", a behaviour that is also not followed by other actinide(V) ions. The observations of Lundqvist (1974) differ from those of Guillaumont (1965, 1968) who indicated the formation of three protactinium(IV) hydrolysis species, PaOH, Pa(OH)2 and PafOHlg, with respective stability constants of log = -0.14, log 2 = -0.52 and log = -1.77 in measurements carried out in 3.0 mol 1 LiClO. Given that there are no supporting data for either of these interpretations, no data are retained for protactinium(IV). 

Liljenzin, J.O. and Rydberg, J, (1966) Complex formation between protactinium and acetylacetone, in Physicochemie du protactinium, Orsay, pp. 255-271. 

Lundqvist, R. (1974) Aqueous chemistry of protactinium(IV). Stability constants for Pa(IV)-acetylacetone complexes. Acta Chem. Scand., 28A, 243-247. 

---