Chlorine pentafluoride is an interhalogen compound with formula ClF5. This colourless gas is a strong oxidant that was once a candidate oxidizer for rockets. The molecule adopts a square pyramidal structure with C4v symmetry,[1] as confirmed by its high-resolution 19F NMR spectrum.[2] It was first synthesized in 1963.[3]
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| ECHA InfoCard | 100.033.734 
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| Properties | |||
| ClF5 | |||
| Molar mass | 130.445 g mol−1 | ||
| Appearance | colorless gas | ||
| Density | 4.5 kg/m3 (g/L) | ||
| Melting point | −103 °C (−153 °F; 170 K) | ||
| Boiling point | −13.1 °C (8.4 °F; 260.0 K) | ||
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| Structure | |||
| Square pyramidal | |||
| Thermochemistry | |||
Std molar |
310.73 J K−1 mol−1 | ||
Std enthalpy of |
−238.49 kJ mol−1 | ||
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |||
Some of the earliest research on the preparation was classified.[4][5] It was first prepared by fluorinationofchlorine trifluoride at high temperatures and high pressures:[4]
NiF2 catalyzes this reaction.[6]
Certain metal fluorides, MClF4 (i.e. KClF4, RbClF4, CsClF4), react with F2 to produce ClF5 and the corresponding alkali metal fluoride.[5]
In a highly exothermic reaction, ClF5 reacts with water to produce chloryl fluoride and hydrogen fluoride:[7]
It is also a strong fluorinating agent. At room temperature it reacts readily with all elements (including otherwise "inert" elements like platinum and gold) except noble gases, nitrogen, oxygen and fluorine.[2]
Chlorine pentafluoride was once considered for use as an oxidizer for rockets. As a propellant, it has a higher maximum specific impulse than ClF3, but with the same difficulties in handling.[4] Due to the hazardous nature of chlorine pentafluoride, it has yet to be used in a large scale rocket propulsion system.
