Rhenium (IV) oxide

Crystal structure
	__ Re 4+ __ O 2−
General
Surname	Rhenium (IV) oxide
other names	Rhenium dioxide
Ratio formula	ReO 2
Brief description	gray-black solid
External identifiers / databases
EC number	234-839-0
ECHA InfoCard	100,031,659
PubChem	82847
ChemSpider	74759
Wikidata	Q2451840
properties
Molar mass	218.21 g mol −1
Physical state	firmly
density	11.4 g cm −3
Melting point	1000 ° C (decomposition)
solubility	almost insoluble in water
safety instructions
GHS labeling of hazardous substances	no GHS pictograms
	no GHS pictograms
H and P phrases	H: no H-phrases
	P: no P-phrases
	As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Rhenium (IV) oxide is an inorganic chemical compound of rhenium from the group of oxides .

Extraction and presentation

Rhenium (IV) oxide can be obtained by reacting rhenium with rhenium (VI) oxide .

{\ displaystyle \ mathrm {Re + 2 \ ReO_ {3} \ longrightarrow 3 \ ReO_ {2}}}

It is also possible to display it by heating ammonium perrhenate in a stream of dry nitrogen , argon or in a vacuum , with the monoclinic or orthorhombic modification occurring depending on the temperature .

{\ displaystyle \ mathrm {2 \ NH_ {4} ReO_ {4} \ longrightarrow 2 \ ReO_ {2} + N_ {2} +4 \ H_ {2} O}}

By reducing rhenate (VII) solutions, it is obtained as an oxide hydrate, which can be easily dehydrated.

Single crystals of the β-oxide can be produced using a CVT (Chemical Vapor Transport) method . For this purpose, rhenium (VI) oxide is first reacted with elemental rhenium with the addition of a few mg of iodine in a melted and evacuated ampoule at 500 ° C to form the polycrystalline oxide. The gray-black oxide is then melted into a new ampoule with about 1% iodine and this is placed in a 2-zone oven so that half of the ampoule is in one of the zones. While half of the ampoule is heated to 850 ° C, the other half is held at 825 ° C. After a reaction time of 3 days (with 0.5 g of oxide initially used), the ampoule is allowed to cool and, after opening, black single crystals of the target compound about 2 to 3 mm in size are obtained, which are often twinned . Should the surface show red discoloration due to oxidation processes during cooling, it can be removed by rinsing with cold, diluted nitric acid

{\ displaystyle \ mathrm {ReO_ {2} + \ I_ {2} \ rightleftharpoons ReO_ {2} I_ {2 (g)}}}

properties

Rhenium (IV) oxide is a gray-black solid. The permanent α-modification that occurs below 300 ° C is irreversibly converted into the β-modification at temperatures above 300 ° C. The α-modification has a monoclinic crystal structure (a = 558 pm, b = 481 pm, c = 558 pm, β = 120.9 °) of the molybdenum (IV) oxide or tungsten (IV) oxide type. The β-modification has an orthorhombic crystal structure with the space group Pbcn (space group no. 60) and the lattice parameters a = 480.9 pm, b = 564.3 pm and c = 460.1 pm. Both modifications show metallic conductivity. They are insoluble in water, bases, non-oxidizing acids. They are soluble in hydrohalic acids ; they react with hydrogen peroxide and nitric acid to form perrhenic acid . With oxygen , a conversion to rhenium (VII) oxide takes place at an elevated temperature and a disproportionation to rhenium and rhenium (VII) oxide takes place in a vacuum at temperatures above 850 ° C. With metal (II) oxides it forms double oxides Me (II) ReO ₃ with a perovskite structure. There is also a hydrate which is in the form of a brown-black X-ray amorphous powder. It loses water at 500 ° C in a vacuum and changes to the anhydrous form. Template: room group / 60

Individual evidence

↑ ^a ^b ^c ^d ^e ^f ^g Georg Brauer (Ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1617.
↑ ^a ^b ^c data sheet Rhenium (IV) oxide, 99.7% trace metals basis from Sigma-Aldrich , accessed on July 28, 2013 ( PDF ).
^ Jean d'Ans, Ellen Lax, Roger Blachnik: Pocket book for chemists and physicists . Springer DE, 1998, ISBN 3-642-58842-5 , pp. 694 ( limited preview in Google Book search).
^ ^A ^b Erwin Riedel: Inorganic Chemistry . Walter de Gruyter, 2004, ISBN 3-11-018168-1 , p. 811 ( limited preview in Google Book search).
↑ DB Rogers et al .: Single crystals of transition-metal dioxides - C. Tungsten dioxide and β-rhenium dioxide . In: FA Cotton (Ed.): Inorganic Syntheses . tape 13 . McGraw-Hill Book Company, Inc., 1972, ISBN 07-013208-9 ( defective ) , p. 135-145 (English).

[brauer-1] ↑ ^a ^b ^c ^d ^e ^f ^g Georg Brauer (Ed.) U. a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume III, Ferdinand Enke, Stuttgart 1981, ISBN 3-432-87823-0 , p. 1617.

[Sigma-2] ta sheet Rhenium (IV) oxide, 99.7% trace metals basis from Sigma-Aldrich , accessed on July 28, 2013 ( PDF ).

[Jean_d’Ans,_Ellen_Lax,_Roger_Blachnik-3] Jean d'Ans, Ellen Lax, Roger Blachnik: Pocket book for chemists and physicists . Springer DE, 1998, ISBN 3-642-58842-5 , pp. 694 ( limited preview in Google Book search).

[Erwin_Riedel-4] A ^b Erwin Riedel: Inorganic Chemistry . Walter de Gruyter, 2004, ISBN 3-11-018168-1 , p. 811 ( limited preview in Google Book search).

[IS13-5] DB Rogers et al .: Single crystals of transition-metal dioxides - C. Tungsten dioxide and β-rhenium dioxide . In: FA Cotton (Ed.): Inorganic Syntheses . tape 13 . McGraw-Hill Book Company, Inc., 1972, ISBN 07-013208-9 ( defective ) , p. 135-145 (English).