Protactinium(V) bromide

Protactinium(V) bromide is an inorganic compound. It is a halide of protactinium, consisting of protactinium and bromine. It is radioactive and has a chemical formula of PaBr₅, which is a red crystal of the monoclinic crystal system.^[2][1]

Protactinium(V) bromide

Names
IUPAC name Protactinium(V) bromide
Identifiers
CAS Number	15608-38-5 Y
3D model (JSmol)	Interactive image
InChI InChI=1S/5BrH.Pa/h5*1H;/q;;;;;+5/p-5 Key: NWILNELACOZBOD-UHFFFAOYSA-I
SMILES Br[Pa](Br)(Br)(Br)Br
Properties
Chemical formula	PaBr5
Molar mass	630.556 g mol−1
Appearance	red solid
Density	4.98 g/cm3
Structure
Crystal structure	monoclinic[1][2]
Space group	P21/c , No. 14
Related compounds
Other anions	Protactinium(V) fluoride Protactinium(V) chloride Protactinium(V) iodide
Other cations	Praseodymium(III) bromide Thorium(IV) bromide Uranium(IV) bromide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Preparation

Protactinium(V) bromide can be obtained by reacting protactinium(V) chloride with boron tribromide at 500 to 550 °C.^[3]

3PaCl₅ + 5BBr₃ → 3PaBr₅ + 5BCl₃

It can also be obtained by reacting protactinium(V) oxide with aluminum bromide at 400 °C.^[4]

Physical properties

Protactinium(V) bromide is an orange-red, crystalline, extremely moisture-sensitive solid that reacts violently with water and ammonia, but is persistent in absolutely dry air. It is insoluble in isopentane, dichloromethane and benzene, and in anhydrous acetonitrile is dissolves to form PaBr₅•4CH₃CN. It comes in several modifications. Below 400 °C as an α-modification and above 400 °C as a β-modification. The α-form has a monoclinic crystal structure of the space group P2₁/c (No. 14) and lattice parameters a = 1296 pm, b = 1282 pm, c = 992 pm, β = 108° and the β-form also has monoclinic crystal structure with space group P2₁/n (No. 14, position 2) and lattice parameters a = 838.5 pm, b = 1120.5 pm, c = 895.0 pm, β = 91.1°.^[3] The β form exists as a dimer. At 400 °C in a vacuum, protactinium(V) bromide sublimes.^[5] A γ-form, which has a β-uranium(V) chloride-type crystal structure, has also been detected.^[6]