Uranium tetrachloride

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Uranium tetrachloride  Uranium Tetrachloride crystal structure

Names
IUPAC name

Uranium(IV) chloride

Other names

Tetrachlorouranium
Uranium tetrachloride
Uranous chloride

Identifiers

CAS Number

* 10026-10-5 Y

3D model (JSmol)

* Interactive image

ChemSpider |

* 19969614 Y

ECHA InfoCard | 100.030.040
EC Number |

* 233-057-7

PubChem CID

* 66210

UNII |

* 8E7IB152RL Y

CompTox Dashboard (EPA)

* DTXSID1064906

InChI

* InChI=1S/4ClH.2U/h4*1H;;/q;;;;2*+2/p-4 Y

Key: AYQSGSWJZFIBLR-UHFFFAOYSA-J Y

* InChI=1/4ClH.2U/h4*1H;;/q;;;;2*+2/p-4

Key: AYQSGSWJZFIBLR-XBHQNQODAS

SMILES

* [U+4].[Cl-].[Cl-].[Cl-].[Cl-]

Properties

Chemical formula

| UCl4
Molar mass | 379.84 g/mol
Appearance  | olive green solid
Density | 4.87 g/cm3
Melting point | 590 °C (1,094 °F; 863 K)
Boiling point | 791 °C (1,456 °F; 1,064 K)

Solubility in water

| Hydrolysis
Solubility | Soluble in hydrochloric acid
Structure

Crystal structure

| Octahedral
Related compounds

Related compounds

| uranium trichloride, uranium pentachloride, uranium hexachloride

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

Chemical compound

Uranium tetrachloride is an inorganic compound, a salt of uranium and chlorine, with the formula UCl4. It is a hygroscopic olive-green solid. It was used in the electromagnetic isotope separation (EMIS) process of uranium enrichment. It is one of the main starting materials for organouranium chemistry.

## Synthesis and structure

[edit]

Single crystals of uranium tetrachloride (field of view about 7 mm)

Uranium tetrachloride is synthesised generally by the reaction of uranium trioxide (UO3) and hexachloropropene. Solvent UCl4 adducts can be formed by a simpler reaction of UI4 with hydrogen chloride in organic solvents.

Uranium tetrachloride also forms the nonahydrate, which can be produced by evaporating a mildly acidic solution of UCl4.[1]

According to X-ray crystallography the uranium centers are eight-coordinate, being surrounded by eight chlorine atoms, four at 264 pm and the other four at 287pm.[2]

## Chemical properties

[edit]

Dissolution in protic solvents is more complicated. When UCl4 is added to water the uranium aqua ion is formed.

UCl4 \+ xH2O → [U(H2O)x]4+ \+ 4Cl−

The aqua ion [U(H2O)x]4+, (x is 8 or 9[3]) is strongly hydrolyzed.

[U(H2O)x]4+ ⇌ [U(H2O)x−1(OH)]3+ \+ H+

The pKa for this reaction is ca. 1.6,[4] so hydrolysis is absent only in solutions of acid strength 1 mol dm−3 or stronger (pH < 0). Further hydrolysis occurs at pH > 3\. Weak chloro complexes of the aqua ion may be formed. Published estimates of the log K value for the formation of [UCl]3+(aq) vary from −0.5 to +3 because of difficulty in dealing with simultaneous hydrolysis.[4]

With alcohols, partial solvolysis may occur.

UCl4 \+ xROH ⇌ UCl4−x(OR)x \+ xHCl

Uranium tetrachloride dissolves in non-protic solvents such as tetrahydrofuran, acetonitrile, dimethyl formamide etc. that can act as Lewis bases. Solvates of formula UCl4Lx are formed which may be isolated. The solvent must be completely free of dissolved water, or hydrolysis will occur, with the solvent, S, picking up the released proton.

UCl4 \+ H2O + S ⇌ UCl3(OH) + SH+ +Cl−

The solvent molecules may be replaced by other ligand in a reaction such as

UCl4 \+ 2Cl− → [UCl6]2−.

The solvent is not shown, just as when complexes of other metal ions are formed in aqueous solution.

Solutions of UCl4 are susceptible to oxidation by air, resulting in the production of complexes of the uranyl ion.

## Applications

[edit]

Uranium tetrachloride is produced commercially by the reaction of carbon tetrachloride with pure uranium dioxide UO2 at 370 °C. It has been used as feed in the electromagnetic isotope separation (EMIS) process of uranium enrichment. Beginning in 1944, the Oak Ridge Y-12 Plant converted UO3 to UCl4 feed for the Ernest O. Lawrence's calutrons. Its major benefit was that the uranium tetrachloride used in the calutrons is not as corrosive as the uranium hexafluoride used in most other enrichment technologies. This process was abandoned in the 1950s. In the 1980s Iraq unexpectedly revived this option as part of its nuclear weapons program. In the enrichment process, uranium tetrachloride is ionized into a uranium plasma.

The uranium ions are then accelerated and passed through a strong magnetic field. After traveling along half of a circle, the beam is split into a region nearer the outside wall, which is depleted, and a region nearer the inside wall, which is enriched in 235U. The large amounts of energy required in maintaining the strong magnetic fields as well as the low recovery rates of the uranium feed material and slower more inconvenient facility operation make this an unlikely choice for large scale enrichment plants.

Work is being done in the use of molten uranium chloride–alkali chloride mixtures as reactor fuels in molten salt reactors. Uranium tetrachloride melts dissolved in a lithium chloride–potassium chloride eutectic have also been explored as a means to recover actinides from irradiated nuclear fuels through pyrochemical nuclear reprocessing.[5]

## Safety

[edit]

Like all water soluble uranium salts, uranium tetrachloride is nephrotoxic (poisonous to the kidney) and can cause severe renal damage and acute renal failure if ingested.

## References

[edit]

1. ^ Thomas Kasperowicz; Niko T. Flosbach; Dennis Grödler; Hannah Kasperowicz; Jörg-M. Neudörfl; Tobias Rennebaum; Mathias S. Wickleder; Markus Zegke (2022). "Solvated Actinoids: Methanol, Ethanol, and Water Adducts of Thorium and Uranium Tetrachloride". European Journal of Inorganic Chemistry. 2022 (31). doi:10.1002/ejic.202200227.
2. ^ Taylor, J.C.; Wilson, P.W. (1973). "A neutron-diffraction study of anhydrous uranium tetrachloride". Acta Crystallogr. B. 29 (9): 1942–1944\. Bibcode:1973AcCrB..29.1942T. doi:10.1107/S0567740873005790.
3. ^ David, F. (1986). "Thermodynamic properties of lanthanide and actinide ions in aqueous solution". Journal of the Less Common Metals. 121: 27–42\. doi:10.1016/0022-5088(86)90511-4.
4. ^ a b IUPAC SC-Database[permanent dead link] A comprehensive database of published data on equilibrium constants of metal complexes and ligands
5. ^ Olander, D. R. and Camahort, J. L. (1966), Reaction of chlorine and uranium tetrachloride in the fused lithium chloride-potassium chloride eutectic. AIChE Journal, 12: 693–699. doi:10.1002/aic.690120414

* v
* t
* e

Uranium compounds

U(II)|

* UB2
* US

U(III)|

* UF3
* UCl3
* UBr3
* UI3
* UP
* U(OH)3
* UH3
* UN

| Organouranium(III) compounds|

* U(C5H5)3

|

U(IV)|

* U(BH4)4
* UC
* UCl4
* UF4
* UBr4
* UI4
* UO2
* UH4
* USi2
* US2
* USe2
* UTe2
* U(SO4)2

| Organouranium(IV) compounds|

* U(C8H8)2
* U(C5H5)4
* U(C5H5)3Cl

|

U(IV,V)|

* U2N3

U(V)|

* UCl5
* UF5
* UBr5
* UI5
* U2O5

U(V,VI)|

* U3O8

U(VI)|

* (NH4)2U2O7
* Na2U2O7
* MgU2O7
* UCl6
* UF6
* U(PO4)2
* UO3
* UN2

| Uranyl compounds|

* Na4UO2(CO3)3
* UO4
* UO2(CH3COO)2
* UO2(CHO2)2
* UO2CO3
* UO2C2O4
* UO2CO3·2(NH4)2CO3
* UO2Cl2
* UO2F2
* UO2(NO3)2
* UO2(OH)2
* (UO2)2(OH)4
* UO2(PO3)2
* UO2(SO4)2
* ZnUO2(CH3COO)4

|

U(XII)|

* UO6 (hypothetical)

* v
* t
* e

Salts and covalent derivatives of the chloride ion

| HCl |  |  |  | He

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LiCl | BeCl2 | B4Cl4
B12Cl12
BCl3
B2Cl4
+BO3 | C2Cl2
C2Cl4
C2Cl6
CCl4

+CO3 | NCl3
ClN3

+NO3 | ClxOy
Cl2O
Cl2O2
ClO
ClO2
Cl2O4
Cl2O6
Cl2O7
ClO4
+O | ClF
ClF3
ClF5 | Ne
NaCl | MgCl2 | AlCl
AlCl3 | Si5Cl12
Si2Cl6
SiCl4 | P2Cl4
PCl3
PCl5
+P | S2Cl2
SCl2
SCl4
+SO4 | Cl2 | Ar
KCl | CaCl
CaCl2 |  | ScCl3 | TiCl2
TiCl3
TiCl4 | VCl2
VCl3
VCl4
VCl5 | CrCl2
CrCl3
CrCl4 | MnCl2
MnCl3 | FeCl2
FeCl3 | CoCl2
CoCl3 | NiCl2 | CuCl
CuCl2 | ZnCl2 | GaCl
GaCl3 | GeCl2
GeCl4 | AsCl3
AsCl5
+As | Se2Cl2
SeCl2
SeCl4 | BrCl | Kr
RbCl | SrCl2 |  | YCl3 | ZrCl2
ZrCl3
ZrCl4 | NbCl3
NbCl4
NbCl5 | MoCl2
MoCl3
MoCl4
MoCl5
MoCl6 | TcCl3
TcCl4 | RuCl2
RuCl3
RuCl4 | RhCl3 | PdCl2 | AgCl | CdCl2 | InCl
InCl2
InCl3 | SnCl2
SnCl4 | SbCl3
SbCl5 | Te3Cl2
TeCl2
TeCl4 | ICl
ICl3 | XeCl
XeCl2
XeCl4
CsCl | BaCl2 | *  | LuCl3 | HfCl4 | TaCl3
TaCl4
TaCl5 | WCl2
WCl3
WCl4
WCl5
WCl6 | ReCl3
ReCl4
ReCl5
ReCl6 | OsCl2
OsCl3
OsCl4
OsCl5 | IrCl2
IrCl3
IrCl4 | PtCl2
PtCl4 | AuCl
(Au[AuCl4])2
AuCl3 | Hg2Cl2
HgCl2 | TlCl
TlCl3 | PbCl2
PbCl4 | BiCl3 | PoCl2
PoCl4 | AtCl | Rn
FrCl | RaCl2 | **  | LrCl3 | RfCl4 | DbCl5 | SgO2Cl2 | BhO3Cl | Hs  | Mt  | Ds  | Rg  | Cn  | Nh  | Fl  | Mc  | Lv  | Ts  | Og

*  | LaCl3 | CeCl3 | PrCl3 | NdCl2
NdCl3 | PmCl3 | SmCl2
SmCl3 | EuCl2
EuCl3 | GdCl3 | TbCl3 | DyCl2
DyCl3 | HoCl3 | ErCl3 | TmCl2
TmCl3 | YbCl2
YbCl3
**  | AcCl3 | ThCl3
ThCl4 | PaCl4
PaCl5 | UCl3
UCl4
UCl5
UCl6 | NpCl3
NpCl4 | PuCl3 | AmCl2
AmCl3 | CmCl3 | BkCl3 | CfCl3
CfCl2 | EsCl2
EsCl3 | FmCl2 | MdCl2 | NoCl2

* v
* t
* e

Halides of actinides

|  | Ac | Th | Pa | U | Np | Pu | Am | Cm | Bk | Cf | Es | Fm

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+6  |  |  |  | UF6
UCl6 | NpF6 | PuF6 | AmF6 | CmF6 |  |  | EsF6 |
+5  |  |  | PaF5
PaCl5
PaBr5
PaI5 | UF5
UCl5
UBr5 | NpF5 | PuF5 |  |  |  |  |  |
+4  |  | ThF4
ThCl4
ThBr4
ThI4 | PaF4
PaCl4
PaBr4
PaI4 | UF4
UCl4
UBr4
UI4 | NpF4
NpCl4
NpBr4 | PuF4 | AmF4 | CmF4 | BkF4 | CfF4 | EsF4 |
+3  | AcF3
AcCl3
AcBr3
AcI3 | ThF3
ThCl3
ThI3 |  | UF3
UCl3
UBr3
UI3 | NpF3
NpCl3
NpBr3
NpI3 | PuF3
PuCl3
PuBr3
PuI3 | AmF3
AmCl3
AmBr3
AmI3 | CmF3
CmCl3
CmBr3
CmI3 | BkF3
BkCl3
BkBr3
BkI3 | CfF3
CfCl3
CfBr3
CfI3 | EsF3
EsCl3
EsBr3
EsI3 | FmCl3
+2  |  | ThF2
ThI2
ThCl2 |  |  |  |  | AmF2
AmCl2
AmBr2
AmI2 |  |  | CfI2
CfCl2 | EsCl2
EsBr2
EsI2 | FmCl2
*[CID]: Compound ID
*[EPA]: U.S. Environmental Protection Agency
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