|Molar mass||273.21 g/mol|
|Melting point||194 °C|
|Boiling point||268 °C|
|Solubility in water||hydrolyzes|
|Solubility||soluble in dry ether, dry alcohol, organic solvents|
|EU Index||Not listed|
|Main hazards||oxidizer, hydrolyzes to release HCl|
|Other anions||Molybdenum(V) fluoride
|Other cations||Chromium(IV) chloride
|Related molybdenum chlorides||Molybdenum(II) chloride
|Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)|
|(what is: / ?)|
Molybdenum(V) chloride is the inorganic compound with the formula [MoCl5]2. This dark volatile solid is used in research to prepare other molybdenum compounds. it is soluble in chlorinated solvents.
Solid state molybdenum pentachloride exists as a dimer with the formula Mo2Cl10. Each molybdenum has local octahedral symmetry and two chlorides bridge between the molybdenum centers. A similar structure is also found for the pentachlorides of W, Nb and Ta. In the gas phase and partly in solution, the dimers partially dissociates to give a monomeric pentahalide. The monomer is paramagnetic, with one unpaired electron per Mo center, reflecting the fact that the formal oxidation state is 5+, leaving one valence electron on the metal center.
Preparation and properties
MoCl5 is a strong oxidant. It is reduced by MeCN to afford an orange complex, MoCl4(MeCN)2, that in turn reacts with THF to give MoCl4(THF)2, a precursor to other molybdenum-containing molecules. MoCl5 is reduced by HBr to form MoBr4. The bromination reaction is conducted in ethylbromide at -50 C, forming MoBr5 as an intermediate. Upon warming to 20 °C, Br2 is produced and the formal oxidation state of molybdenum changes from +5 to +4. The net transformation is shown in the equation:
- 2 MoCl5 + 10 HBr → 2 MoBr4 + 10 HCl + Br2
MoBr4 reacts with THF to give the Mo(III) species mer-MoBr3(THF)3.
MoCl5 is a good Lewis acid toward non-oxidizable ligands. It forms an adduct with chloride to form [MoCl6]-. In organic synthesis, the compound finds occasional use in chlorinations, deoxygenation, and oxidative coupling reactions.
MoCl5 is an aggressive oxidant and readily hydrolyzes to release HCl.
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