13773-81-4

Basic information

• Product Name: Krypton(II) difluoride
• Synonyms: Krypton difluoride;Krypton(II) difluoride
• CAS NO: 13773-81-4
• Molecular Formula: F₂Kr
• Molecular Weight: 121.8
• Mol File: 13773-81-4.mol
• Article Data: 7

Chemical Properties

• Melting Point: decomposes at ~25℃ [KIR78]
• Appearance: /colorless tetragonal crystals
• Density: (calc) 3.24
• CAS DataBase Reference: Krypton(II) difluoride(CAS DataBase Reference)
• NIST Chemistry Reference: Krypton(II) difluoride(13773-81-4)
• EPA Substance Registry System: Krypton(II) difluoride(13773-81-4)

Safety Data

• Hazardous Substances Data: 13773-81-4(Hazardous Substances Data)

Usage

Chemical Properties

colorless solid; decomposes rapidly at room temp; tetr, a=0.6533 nm, c=0.5831 nm; vapor pressure at 0°C is 29mm Hg; thermodynamically unstable, can be stored at ?78°C; prepared by electrical discharge of Kr and F2 at ?183°C; used in certain types of electric light bulbs [MER06] [KIR78] [COT88]

Physical properties

White tetragonal crystal; sublimes under vacuum at 0°C; decomposes slowly at 25°C; density 3.24 g/cm3; reacts with water; vapor pressure 30 torr at 0°C; slightly soluble in liquid fluorine.

Uses

As gas filler in special purpose electric bulbs. To initiate and sustain the arc in metal-vapor discharge tubes, such as mercury and sodium vapor lamps. To determine surface areas of fine solids by adsorption techniques.

Preparation

Krypton difluoride may be prepared by the reaction of krypton with fluorine in an electric discharge at low pressure and liquid oxygen temperature. Also it may be made by irradiating krypton with ultraviolet rays in a fluorine—argon gas mixture at liquid helium temperature (-196°F). Kr + F2 → KrF2 The product can be stored at -78°C without decomposition.

InChI:InChI=1/F2Kr/c1-3-2

Upstream product

• 75-71-8 Dichlorodifluoromethane 
• 7782-41-4 fluorine 
• 102110-05-4 KrF₂CrF₄O 
• 13693-05-5 platinum hexafluoride 
• 13693-07-7 rhodium hexafluoride 

Downstream Products

• 7664-39-3 hydrogen fluoride 
• 13709-56-3 PuF₄ 
• 13693-06-6 plutonium hexafluoride 
• 77744-91-3 KrF₂WOF₄ 
• 80937-33-3 oxygen 
• 7783-82-6 tungsten(VI) fluoride 
• 7783-81-5 uranium hexafluoride 
• 15195-58-1 manganese tetrafluoride 
• 10060-10-3 cerium tetrafluoride 
• 184851-42-1 chlorine pentafluoride 
• 13709-42-7 neodymium(III) fluoride 
• 36781-15-4 terbium tetrafluoride 
• 7783-54-2 nitrogen trifluoride 
• 13776-62-0 trans-1,2-difluorodiazine 

Relevant articles and documents

X-ray crystal structures of α-KrF2, [KrF][MF6] (M = As, Sb, Bi), [Kr2F3][SbF6]·KrF2, [Kr2F3]2[SbF6] 2·KrF2, and [Kr2F3][AsF6]·[KrF][AsF6];

The crystal structures of α-KrF2 and salts containing the KrF+ and Kr2F3+ cations have been investigated for the first time using low-temperature single-crystal X-ray diffraction. The low-temperature α-phase of KrF2 crystallizes in the tetragonal space group I4/mmm with a = 4.1790(6) A, c = 6.489(1) A, Z = 2, V = 113.32(3) A3, R1 = 0.0231, and wR2 = 0.0534 at - 125 °C. The [KrF][MF6] (M = As, Sb, Bi) salts are isomorphous and isostructural and crystallize in the monoclinic space group P21/c with Z = 4. The unit cell parameters are as follows: β-[KrF][AsF6], a = 5.1753(2) A, b = 10.2019(7) A, c = 10.5763(8) A, β = 95.298(2)°, V = 556.02(6) A3, R1 = 0.0265, and wR2 = 0.0652 at - 120°C; [KrF][SbF6],a = 5.2922(6) A, b = 10.444(1) A, c = 10.796(1) A, β = 94.693-(4)°, V = 594.73(1) A3, R1 R, = 0.0266, wR2 = 0.0526 at - 113 °C; [KrF][BiF6], a = 5.336(1) A, b = 10.513(2) A, c = 11.046(2) A, β = 94.79(3)°, V = 617.6(2) A3, R1 = 0.0344, and wR2 = 0.0912 at - 130 °C. The Kr2F3+ cation was investigated in [Kr2F3][SbF6]·KrF2, [Kr2F3]2[SbF6] 2·KrF2, and [Kr2F3][AsF6]·[KrF][AsF6]. [Kr2F3]2[SbF6] 2·KrF2 crystallizes in the monoclinic P21/c space group with Z = 4 and a = 8.042(2) A, b = 30.815(6) A, c = 8.137(2) A, β = 111.945(2)°, V = 1870.1(7) A3, R1 = 0.0376, and wR2 = 0.0742 at -125 °C. [Kr2F3][SbF6]·KrF2 crystallizes in the triclinic P1 space group with Z = 2 and a = 8.032(3) A, b = 8.559(4) A, c = 8.948(4) A, α = 69.659(9)°, β = 63.75(1)°, γ = 82.60(1)°, V = 517.1(4) A3, R1 = 0.0402, and wR2 = 0.1039 at -113 °C. [Kr2F3][AsF6]·[KrF][AsF6] crystallizes in the monoclinic space group P21/c with Z = 4 and a = 6.247(1) A, b = 24.705(4) A, c = 8.8616(6) A, β = 90.304(6)°, V = 1367.6(3) A3, R1 = 0.0471 and wR2 = 0.0958 at -120 °C. The terminal Kr-F bond lengths of KrF+ and Kr2F3+ are very similar, exhibiting no crystallographically significant variation in the structures investigated (range, 1.765(3)-1.774(6) A and 1.780(7)-1.805(5) A, respectively). The Kr-F bridge bond lengths are significantly longer, with values ranging from 2.089(6) to 2.140(3) A in the KrF+ salts and from 2.027(5) to 2.065(4) A in the Kr2F3+ salts. The Kr-F bond lengths of KrF2 in [Kr2F3][SbF6]·KrF2 and [Kr2F3]2[SbF6] 2·KrF2 range from 1.868(4) to 1.888(4) A and are similar to those observed in α-KrF2 (1.894(5) A). The synthesis and Raman spectrum of the new salt, [Kr2F3][PF6]· nKrF2, are also reported. Electron structure calculations at the Hartree-Fock and local density-functional theory levels were used to calculate the gas-phase geometries, charges, Mayer bond orders, and Mayer valencies of KrF+, KrF2, Kr2F3+, and the ion pairs, [KrF][MF6] (M = P, As, Sb, Bi), and to assign their experimental vibrational frequencies.

Synthesis and crystal structure of (Xe2F11+)2NiF6 2-

(Xe2F11+)2NiF6 2- has been prepared by the reaction between nickel difluoride, krypton difluoride, and xenon hexafluoride in anhydrous hydrogen fluoride. (Xe2F11+)2NiF6 2- crystallizes in the monoclinic space group I2/a with a = 17.477 (5) ?, b = 5.384 (6) ?, c = 21.300 (8) ?, β = 102.83 (3)°, V = 1954.2 ?3, Z = 4, and dc = 3.792 g cm-3. A structure determination using three-dimensional Mo Kα X-ray data resulted in conventional R and Rw factors of 0.070 and 0.094, respectively, for 1355 unique reflections for which I > 3σ(I). The anion NiF62- is essentially octahedral; Ni-F distances range from 1.77 (1) to 1.79 (1) ?. The Xe2Fu+ ion consists of two XeF5 groups bridged by an additional common fluorine atom. The bridge bond lengths are 2.35 (1) and 2.21 (1) ? with a bridge angle of 140.3 (6)°. (Xe2F11+)2NiF6 2- represents the first known crystal structure of a compound with two Xe2F11+ cations.

Formation of actinide hexafluorides at ambient temperatures with krypton difluoride

A second low-temperature agent, krypton difluoride, for generating volatile plutonium hexafluoride is reported (dioxygen difluoride is the only other reported agent). Plutonium hexafluoride is formed at ambient or lower temperature by the treatment of various solid substrates with krypton difluoride. Volatilization of uranium and neptunium from solid substrates using gaseous krypton difluoride is also reported for the first time. The formation of actinide hexafluorides has been confirmed for the reaction of krypton difluoride in anhydrous HF with UO2 and with uranium and neptunium fluorides at ambient temperatures. Treatment of americium dioxide with krypton difluoride did not yield americium hexafluoride under the conditions studied.