Chlorine trifluoride oxide

Chlorine oxide trifluoride or chlorine trifluoride oxide is a corrosive liquid molecular compound with formula ClOF₃. It was developed secretly as a rocket fuel oxidiser.

Chlorine trifluoride oxide

Names
IUPAC name trifluoro(oxo)-λ5-chlorane
Identifiers
CAS Number	30708-80-6[1]
3D model (JSmol)	Interactive image
PubChem CID	15388485
InChI InChI=1S/ClF3O/c2-1(3,4)5 Key: QPKQQPNQDSQNHS-UHFFFAOYSA-N
SMILES O=Cl(F)(F)F
Properties
Chemical formula	ClF3O
Molar mass	108.44 g·mol^−1
Density	1.865
Melting point	−42 °C (−44 °F; 231 K)
Boiling point	29 °C (84 °F; 302 K)
Structure
Crystal structure	monoclinic
Space group	C2/m
Lattice constant	a = 9.826, b = 12.295, c = 4.901 α = 90°, β = 90.338°, γ = 90°[2]
Lattice volume (V)	592.1
Formula units (Z)	8
Hazards
GHS pictograms
GHS Signal word	Danger
Related compounds
Related compounds	BrOF3; IOF3
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Production

Chlorine oxide trifluoride was originally made at Rocketdyne[3] by treating chlorine monoxide with fluorine. Other substances that could react with fluorine to make it includes sodium chlorite (NaClO₂), and chlorine nitrate (ClONO₂). The first published production method was a reaction of chlorine monoxide with oxygen difluoride (OF₂). Yet other production methods are reactions between ClO₂F or ClO₃F and chlorine fluorides.[4] A safer approach is the use chlorine nitrate with fluorine.

Reactions

As a Lewis base it can lose a fluoride ion to Lewis acids, yielding the difluorooxychloronium(V) cation (ClOF₂⁺).[5] Compounds with this include: ClOF₂BF₄, ClOF₂PF₆, ClOF₂AsF₆, ClOF₂SbF₆, ClOF₂BiF₆, ClOF₂VF₆, ClOF₂NbF₆, ClOF₂TaF₆, ClOF₂UF₆, ClOF₂, (ClOF₂)₂SiF₆, ClOF₂MoOF₅, ClOF₂Mo₂O₄F₉,[4] ClOF₂PtF₆.[6]

Functioning as a Lewis acid, it can gain a fluoride ion from a strong base to yield a tetrafluorooxychlorate(V) anion: ClOF₄⁻ ion.[7] These include KClOF₄, RbClOF₄, and CsClOF₄.[8] This allows purification of ClOF₃, as at room temperature a solid complex is formed, but this decomposes between 50 and 70 °C. Other likely impurities either will not react with alkali fluoride, or if they do will not easily decompose.[3]

Chlorine trifluoride oxide fluoridates various materials such as chlorine monoxide, chlorine, glass or quartz.[3] ClOF₃ + Cl₂O → 2ClF + ClO₂F;[6] 2ClOF₃ + 2Cl₂ → 6ClF + O₂ at 200 °C[6]

Chlorine trifluoride oxide adds to chlorine fluorosulfate, ClOF₃ + 2ClOSO₂F → S₂O₅F₂ + FClO₂ + 2ClF. The reaction also produces SO₂F₂.[3]

Chlorine trifluoride oxide can fluoridate and add oxygen in the same reaction, reacting with molybdenum pentafluoride, silicon tetrafluoride, tetrafluorohydrazine (over 100 °C), HNF₂, and F₂NCOF. From HNF₂ the main result was NF₃O. From MoF₅, the results were MoF₆ and MoOF₄.[3]

It reacts explosively with hydrocarbons.[3] With small amounts of water, ClO₂F is formed along with HF.[3]

Over 280 °C ClOF₃ decomposes to oxygen and chlorine trifluoride.[3]

Properties

The boiling point of chlorine trifluoride oxide is 29 °C.[9]

The shape of the molecule is a trigonal bipyramid, with two fluorine atoms at the top and bottom (apex) (F_a) and an electron pair, oxygen and fluorine (F_e) on the equator.[7] The Cl=O bond length is 1.405 Å, Cl-F_e 1.603 Å, other Cl-F_a 1.713 Å, ∠F_eClO=109° ∠F_aClO=95°, ∠F_aClF_e=88°. The molecule is polarised, Cl has a +1.76 charge, O has −0.53, equatorial F has −0.31 and apex F has −0.46. The total dipole moment is 1.74 D.[10]

References

1. Urben, Peter (2017). Bretherick's Handbook of Reactive Chemical Hazards. Elsevier. p. 784. ISBN 9780081010594.
2. Ellern, Arkady; Boatz, Jerry A.; Christe, Karl O.; Drews, Thomas; Seppelt, Konrad (September 2002). "The Crystal Structures of ClF₃O, BrF₃O, and [NO]⁺[BrF₄O]^–". Zeitschrift für anorganische und allgemeine Chemie. 628 (9–10): 1991–1999. doi:10.1002/1521-3749(200209)628:9/10<1991::AID-ZAAC1991>3.0.CO;2-1.
3. Advances in Inorganic Chemistry and Radiochemistry. Academic Press. 1976. pp. 331–333. ISBN 9780080578675.
4. Holloway, John H.; Laycock, David (1983). Advances in Inorganic Chemistry. Academic Press. pp. 178–179. ISBN 9780080578767.
5. Christe, Karl O.; Curtis, E. C.; Schack, Carl J. (September 1972). "Chlorine trifluoride oxide. VII. Difluorooxychloronium(V) cation, ClF₂O⁺. Vibrational spectrum and force constants". Inorganic Chemistry. 11 (9): 2212–2215. doi:10.1021/ic50115a046.
6. Schack, Carl J.; Lindahl, C. B.; Pilipovich, Donald.; Christe, Karl O. (September 1972). "Chlorine trifluoride oxide. IV. Reaction chemistry". Inorganic Chemistry. 11 (9): 2201–2205. doi:10.1021/ic50115a043.
7. Christe, K.O.; Schack, C.J. (1976). Chlorine Oxyfluorides. Advances in Inorganic Chemistry and Radiochemistry. 18. pp. 319–398. doi:10.1016/S0065-2792(08)60033-3. ISBN 9780120236183.
8. Christe, Karl O.; Schack, Carl J.; Pilipovich, Donald.; Christe, Karl O. (September 1972). "Chlorine trifluoride oxide. V. Complex formation with Lewis acids and bases". Inorganic Chemistry. 11 (9): 2205–2208. doi:10.1021/ic50115a044.
9. Pilipovich, Donald.; Lindahl, C. B.; Schack, Carl J.; Wilson, R. D.; Christe, Karl O. (September 1972). "Chlorine trifluoride oxide. I. Preparation and properties". Inorganic Chemistry. 11 (9): 2189–2192. doi:10.1021/ic50115a040.
10. Oberhammer, Heinz.; Christe, Karl O. (January 1982). "Gas-phase structure of chlorine trifluoride oxide, ClF₃O". Inorganic Chemistry. 21 (1): 273–275. doi:10.1021/ic00131a050.