Perrhenic acid

Perrhenic acid

Names
IUPAC name Perrhenic(VII) acid
Other names Hydrated rhenium(VII) oxide
Identifiers
CAS Number	13768-11-1 N
3D model (Jmol)	Interactive image
ChemSpider	21106462 Y
ECHA InfoCard	100.033.968
RTECS number	TT4550000
InChI InChI=1S/2H2O.7O.2Re/h2*1H2;;;;;;;;; Y Key: JOTGKJVGIIKFIQ-UHFFFAOYSA-N Y InChI=1/2H2O.7O.2Re/h2*1H2;;;;;;;;;/rH4O9Re2/c1-10(2,3)9-11(4,5,6,7)8/h4-5H2 Key: JOTGKJVGIIKFIQ-SEUCOXMMAB
SMILES [OH2][Re](=O)(=O)(=O)([OH2])O[Re](=O)(=O)=O
Properties
Chemical formula	H 4O 9Re 2 (solid) HReO 4 (gas)
Molar mass	251.2055 g/mol
Appearance	Pale yellow solid
Melting point	°C (? K)
Boiling point	sublimes
Solubility in water	Soluble
Acidity (pKa)	-1.25
Structure
Coordination geometry	octahedral-tetrahedral (solid) tetrahedral (gas)
Hazards
Main hazards	Corrosive
R-phrases	R34
S-phrases	S26, S36/37, S39, S45
NFPA 704	3
Flash point	Non-flammable
Related compounds
Related compounds	Re 2O 7, Mn 2O 7
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Perrhenic acid is the chemical compound with the formula Re
2O
7(OH
2)
2. It is obtained by evaporating aqueous solutions of Re
2O
7. Conventionally, perrhenic acid is considered to have the formula HReO
4, and a species of this formula forms when rhenium(VII) oxide sublimes in the presence of water or steam. When a solution of Re
2O
7 is kept for a period of months, it breaks down and crystals of HReO
4·H
2O are formed, which contain tetrahedral ReO−
4 For most purposes, perrhenic acid and rhenium(VII) oxide are used interchangeably. Rhenium can be dissolved in nitric or concentrated sulfuric acid to produce perrhenic acid.

The structure of solid perrhenic acid is [O
3Re-O-ReO
3(H
2O)
2]. This species is a rare example of a metal oxide coordinated to water—most often metal-oxo-aquo species are unstable with respect to the corresponding hydroxides: