Names | |
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IUPAC name
Uranium(IV) chloride
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Other names
Tetrachlorouranium
Uranium tetrachloride Uranous chloride |
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Identifiers | |
10026-10-5 | |
3D model (Jmol) | Interactive image |
ChemSpider | 19969614 |
ECHA InfoCard | 100.030.040 |
UNII | 8E7IB152RL |
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Properties | |
UCl4 | |
Molar mass | 379.84 g/mol |
Density | 4.87 g/cm3 |
Melting point | 590 °C (1,094 °F; 863 K) |
Boiling point | 791 °C (1,456 °F; 1,064 K) |
Structure | |
Octahedral | |
Related compounds | |
Related compounds
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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).
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what is ?) | (|
Infobox references | |
Uranium tetrachloride (UCl4) is compound of uranium in oxidation state +4. It was used in the electromagnetic isotope separation (EMIS) process of uranium enrichment. It is one of the main starting materials for organouranium chemistry.
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 is a hygroscopic, dark green solid, which sublimes in a high vacuum at ca. 500 °C. The crystal structure shows the uranium to be surrounded by eight chlorine atoms, four at 264 pm and the other four at 287pm. The molecule UCl4 is a Lewis acid and dissolves in solvents that can act as non-protic Lewis bases.
Dissolution in protic solvents is more complicated. When UCl4 is added to water the uranium aqua ion is formed.
The aqua ion [U(H2O)x]4+, (x is 8 or 9) is strongly hydrolyzed.
The pKa for this reaction is ca. 1.6, 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.
With alcohols, partial solvolysis may occur.
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.