Caesium fluoride

Names
IUPAC name

Caesium fluoride

Other names

Cesium fluoride

Identifiers

CAS Number

* 13400-13-0 Y

3D model (JSmol)

* Interactive image

ChemSpider |

* 24179 Y

EC Number |

* 236-487-3

PubChem CID

* 25953

RTECS number |

* FK9650000

UNII |

* T76A371HJR

InChI

* InChI=1S/Cs.FH/h;1H/q+1;/p-1 Y

Key: XJHCXCQVJFPJIK-UHFFFAOYSA-M Y

* InChI=1/Cs.FH/h;1H/q+1;/p-1

Key: XJHCXCQVJFPJIK-REWHXWOFAY

SMILES

* [F-].[Cs+]

Properties

Chemical formula

| CsF
Molar mass | 151.903 g/mol[1]
Appearance  | white crystalline solid
Density | 4.64 g/cm3[1]
Melting point |  703 °C (1,297 °F; 976 K)[1]
Boiling point |  1,251 °C (2,284 °F; 1,524 K) (2,284 °F; 1,524 K)

Solubility in water

| 573.0 g/100 mL (25 °C)[1]
Solubility | Insoluble in acetone, diethyl ether, pyridine and ethanol
191 g/100 mL in methanol.
Basicity (pKb)  | −744 kJ/mol

Magnetic susceptibility (χ)

| −44.5·10−6 cm3/mol[2]

Refractive index (nD)

| 1.477
Structure

Crystal structure

| cubic, cF8

Space group

| Fm3m, No. 225[3]

Lattice constant

a = 0.6008 nm[3]

Lattice volume (V)

| 0.2169 nm3[3]

Formula units (Z)

| 4

Coordination geometry

| Octahedral

Dipole moment

| 7.9 D
Thermochemistry

Heat capacity (C)

| 51.1 J/mol·K[4]

Std molar
entropy (S ~~o~~ 298)

| 92.8 J/mol·K[4]

Std enthalpy of
formation (ΔfH⦵298)

| −553.5 kJ/mol[4]

Gibbs free energy (ΔfG˚)

| −525.5 kJ/mol[4]
Hazards
Main hazards | toxic
Safety data sheet | External MSDS
GHS pictograms |
GHS Signal word | Danger

GHS hazard statements

| H301, H311, H315, H318, H331, H361f

GHS precautionary statements

| P201, P202, P260, P261, P264, P270, P271, P280, P281, P301+310, P301+330+331, P302+352, P303+361+353, P304+340, P305+351+338, P308+313, P310, P311, P312, P321, P322, P330, P332+313, P361, P362
NFPA 704 (fire diamond)  |

Flash point | Non-flammable
Related compounds

Other anions

| Caesium chloride
Caesium bromide
Caesium iodide
Caesium astatide

Other cations

| Lithium fluoride
Sodium fluoride
Potassium fluoride
Rubidium fluoride
Francium fluoride

Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

N verify (what is YN ?)
Infobox references

Caesium fluoride (cesium fluoride in American English) is an inorganic compound with the formula CsF. A hygroscopic white salt, caesium fluoride is used in the synthesis of organic compounds as a source of the fluoride anion.[5] The compound is noteworthy from the pedagogical perspective as caesium also has the highest electropositivity of all commonly available elements and fluorine has the highest electronegativity.

## Contents

* 1 Synthesis and properties
* 2 Structure
* 3 Applications in organic synthesis
* 3.1 As a base
* 3.2 Formation of Cs-F bonds
* 3.3 Deprotection agent
* 4 Precautions
* 5 References

## Synthesis and properties

Crystalline CsF chains grown inside double-wall carbon nanotubes.[6]

Caesium fluoride can be prepared by the reaction of caesium hydroxide (CsOH) with hydrofluoric acid (HF) and the resulting salt can then be purified by recrystallization. The reaction is shown below:

CsOH + HF → CsF + H2O

Using the same reaction, another way to create caesium fluoride is to treat caesium carbonate (Cs2CO3) with hydrofluoric acid and again, the resulting salt can then be purified by recrystallization. The reaction is shown below:

Cs2CO3 \+ 2 HF → 2 CsF + H2O + CO2

CsF is more soluble than sodium fluoride or potassium fluoride in organic solvents. It is available in its anhydrous form, and if water has been absorbed, it is easy to dry by heating at 100 °C for two hours in vacuo.[7] CsF reaches a vapor pressure of 1 kilopascal at 825 °C, 10 kPa at 999 °C, and 100 kPa at 1249 °C.[8]

## Structure

Caesium fluoride has the halite structure, which means that the Cs+ and F− pack in a cubic closest packed array as do Na+ and Cl− in sodium chloride.[3] Unlike sodium chloride, caesium fluoride's anion is smaller than its cation, so it is the anion size that sterically inhibits larger coordination numbers than six under normally encountered conditions. A larger halide ion would allow for the eight-coordination seen in other caesium halide crystals.

## Applications in organic synthesis

Being highly dissociated, CsF is a more reactive source of fluoride than related alkali metal salts. CsF is an alternative to tetra-n-butylammonium fluoride (TBAF) and TAS-fluoride (TASF).

### As a base

As with other soluble fluorides, CsF is moderately basic, because HF is a weak acid. The low nucleophilicity of fluoride means it can be a useful base in organic chemistry.[9] CsF gives higher yields in Knoevenagel condensation reactions than KF or NaF.[10]

### Formation of Cs-F bonds

Caesium fluoride serves as a source of fluoride in organofluorine chemistry. Similarly to potassium fluoride, CsF reacts with hexafluoroacetone to form a stable perfluoroalkoxide salt.[11] It will convert electron-deficient aryl chlorides to aryl fluorides (Halex process), although potassium fluoride is more commonly used.

### Deprotection agent

Due to the strength of the Si–F bond, fluoride is useful for desilylation reactions, i.e., cleavage of Si-O bonds in organic synthesis.[12] CsF is commonly used for such reactions. Solutions of caesium fluoride in THF or DMF attack a wide variety of organosilicon compounds to produce an organosilicon fluoride and a carbanion, which can then react with electrophiles, for example:[10]

500px

## Precautions

Like other soluble fluorides, CsF is moderately toxic.[13] Contact with acid should be avoided, as this forms highly toxic/corrosive hydrofluoric acid. The caesium ion (Cs+) and caesium chloride are generally not considered toxic.[14]

## References

1. ↑ 1.0 1.1 1.2 1.3 Haynes, William M., ed (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.57. ISBN 1439855110.
2. ↑ Haynes, William M., ed (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 4.132. ISBN 1439855110.
3. ↑ 3.0 3.1 3.2 3.3 Davey, Wheeler P. (1923). "Precision Measurements of Crystals of the Alkali Halides". Physical Review 21 (2): 143–161. doi:10.1103/PhysRev.21.143. Bibcode: 1923PhRv...21..143D.
4. ↑ 4.0 4.1 4.2 4.3 Haynes, William M., ed (2011). CRC Handbook of Chemistry and Physics (92nd ed.). Boca Raton, FL: CRC Press. p. 5.10. ISBN 1439855110.
5. ↑ Friestad, Gregory K.; Branchaud, Bruce P.; Navarrini, Walter; Sansotera, Maurizio (2007). "Cesium Fluoride". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rc050.pub2. ISBN 978-0-471-93623-7.
6. ↑ Senga, Ryosuke; Suenaga, Kazu (2015). "Single-atom electron energy loss spectroscopy of light elements". Nature Communications 6: 7943. doi:10.1038/ncomms8943. PMID 26228378. Bibcode: 2015NatCo...6.7943S. (Supplementary information)
7. ↑ Friestad, G. K.; Branchaud, B. P. (1999). Handbook of Reagents for Organic Synthesis: Acidic and Basic Reagents. New York: Wiley. pp. 99–103. ISBN 978-0-471-97925-8.
8. ↑ Lide, D. R., ed (2005). "Vapor Pressure". CRC Handbook of Chemistry and Physics (86th ed.). Boca Raton (FL): CRC Press. p. 6.63. ISBN 0-8493-0486-5. http://www.physics.nyu.edu/kentlab/How_to/ChemicalInfo/VaporPressure/morepressure.pdf.
9. ↑ Greenwood, Norman N.; Earnshaw, Alan (1984). Chemistry of the Elements. Oxford: Pergamon Press. pp. 82–83. ISBN 978-0-08-022057-4. https://books.google.com/books?id=OezvAAAAMAAJ&q=0-08-022057-6&dq=0-08-022057-6&source=bl&ots=m4tIRxdwSk&sig=XQTTjw5EN9n5z62JB3d0vaUEn0Y&hl=en&sa=X&ei=UoAWUN7-EM6ziQfyxIDoCQ&ved=0CD8Q6AEwBA.
10. ↑ 10.0 10.1 Fiorenza, M; Mordini, A; Papaleo, S; Pastorelli, S; Ricci, A (1985). "Fluoride ion induced reactions of organosilanes: the preparation of mono and dicarbonyl compounds from β-ketosilanes". Tetrahedron Letters 26 (6): 787–788. doi:10.1016/S0040-4039(00)89137-6.
11. ↑ Evans, F. W.; Litt, M. H.; Weidler-Kubanek, A. M.; Avonda, F. P. (1968). "Formation of adducts between fluorinated ketones and metal fluorides". Journal of Organic Chemistry 33 (5): 1837–1839. doi:10.1021/jo01269a028.
12. ↑ Smith, Adam P.; Lamba, Jaydeep J. S.; Fraser, Cassandra L. (2002). "Efficient Synthesis of Halomethyl-2,2'-bipyridines: 4,4'-Bis(chloromethyl)-2,2'-bipyridine". Organic Syntheses 78: 82. http://www.orgsyn.org/demo.aspx?prep=v78p0082. ;  Collective Volume, 10, pp. 107
13. ↑ "MSDS Listing for cesium fluoride". April 27, 1993. http://www.hazard.com/msds/f2/bms/bmsqc.html.
14. ↑ "MSDS Listing for cesium chloride". JT Baker. January 16, 2006. http://hazard.com/msds/mf/baker/baker/files/c1903.htm.

* v
* t
* e

Caesium compounds

* CsBr
* CsCl
* CsClO4
* Cs2CrO4
* CsF
* CsH
* CsI
* CsLiB6O10
* CsNO3
* CsOH
* Cs2CO3
* CsHCO3
* Cs2SO4
* CsC2H3O2
* Cs2O
* Cs2TiO3
* Cs2WO4
* CsAu
* CsHSO4

* v
* t
* e

Salts and covalent derivatives of the fluoride ion

HF |  |  |  | He

|
|
|
|

LiF | BeF2 | BF
BF3
B2F4 | CF4
other compounds | NF3
FN3
N2F2
N2F4
NF5§  | F2O
F2O2
other compounds | F2 | Ne
NaF | MgF2 | AlF
AlF3 | SiF4 | P2F4
PF3
PF5 | S2F2
SF2
SF4
SF6 | ClF
ClF3
ClF5 | Ar
KF | CaF
CaF2 | ScF3 | TiF2
TiF3
TiF4 | VF2
VF3
VF4
VF5 | CrF2
CrF3
CrF4
CrF5
CrF6§  | MnF2 | FeF2
FeF3 | CoF2
CoF3 | NiF2 | CuF
CuF2 | ZnF2 | GaF2
GaF3 | GeF2
GeF4 | AsF3
AsF5 | Se2F2
SeF4
SeF6 | BrF
BrF3
BrF5 | KrF2
RbF | SrF
SrF2 | YF3 | ZrF3
ZrF4 | NbF4
NbF5 | MoF2
MoF3
MoF4
MoF5
MoF6 | TcF4
TcF6 | RuF3
RuF5
RuF6 | RhF3
RhF5
RhF6 | PdF2 | AgF | CdF2 | InF
InF2
InF3 | SnF2
SnF4 | SbF3
SbF5 | Te3F2
TeF4
TeF6 | IF
IF3</br>IF5</br>IF7 | XeF2
XeF4
XeF6
CsF | BaF2 |  | HfF4 | TaF5 | WF2
WF3
WF4
WF5
WF6 | Re3F9
ReF4
ReF5
ReF6
ReF7 | OsF4
OsF5
OsF6 | IrF2
IrF3
IrF4
IrF5
IrF6 | PtF2
PtF4
PtF5
PtF6 | AuF
AuF3
Au2F10
AuF5•F2 | Hg2F2
HgF2
HgF4 | TlF | PbF2
PbF4 | BiF3
BiF5 | PoF2
PoF4
PoF6 | AtF  | RnF2
FrF | RaF2 |  | Rf  | Db  | Sg  | Bh  | Hs  | Mt  | Ds  | Rg  | Cn  | Nh  | Fl  | Mc  | Lv  | Ts  | Og
| ↓  |  |
LaF3 | CeF3
CeF4 | PrF3 | NdF2,
NdF3 | PmF3 | SmF2,
SmF3 | EuF2,
EuF3 | GdF3 | TbF3 | DyF2,
DyF3 | HoF3 | ErF3 | TmF2
TmF3 | YbF2
YbF3 | LuF3
AcF3 | ThF4 | PaF5 | UF3
UF4
UF5
UF6 | NpF4
NpF6 | PuF3
PuF6 | AmF2
AmF3 | CmF3 | BkF3 | CfF3 | EsF3 | Fm  | Md  | No  | LrF3

§ means the substance has not been made.

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*[CID]: Compound ID
*[H301]: Toxic if swallowed
*[H311]: Toxic in contact with skin
*[H315]: Causes skin irritation
*[H318]: Causes serious eye damage
*[H331]: Toxic if inhaled
*[H361f]: Suspected of damaging fertility
*[P201]: Obtain special instructions before use
*[P202]: Do not handle until all safety precautions have been read and understood
*[P260]: Do not breathe dust/fume/gas/mist/vapours/spray
*[P261]: Avoid breathing dust/fume/gas/mist/vapours/spray
*[P264]: Wash … thoroughly after handling
*[P270]: Do not eat, drink or smoke when using this product
*[P271]: Use only outdoors or in a well-ventilated area
*[P280]: Wear protective gloves/protective clothing/eye protection/face protection
*[P281]: Use personal protective equipment as required
*[P301+310]: IF SWALLOWED: Immediately call a POISON CENTER or doctor/physician
*[P301+330+331]: IF SWALLOWED: Rinse mouth. Do NOT induce vomiting
*[P302+352]: IF ON SKIN: Wash with soap and water
*[P303+361+353]: IF ON SKIN (or hair): Remove/Take off immediately all contaminated clothing. Rinse skin with water/shower
*[P304+340]: IF INHALED: Remove victim to fresh air and keep at rest in a position comfortable for breathing
*[P305+351+338]: IF IN EYES: Rinse continuously with water for several minutes. Remove contact lenses if present and easy to do – continue rinsing
*[P308+313]: IF exposed or concerned: Get medical advice/attention
*[P310]: Immediately call a POISON CENTER or doctor/physician
*[P311]: Call a POISON CENTER or doctor/physician
*[P312]: Call a POISON CENTER or doctor/physician if you feel unwell
*[P321]: Specific treatment (see … on this label)
*[P322]: Specific measures (see … on this label)
*[P330]: Rinse mouth
*[P332+313]: If skin irritation occurs: Get medical advice/attention
*[P361]: Remove/Take off immediately all contaminated clothing
*[P362]: Take off contaminated clothing and wash before reuse
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