|Molar mass||273.21 g/mol|
|Melting point||194 °C (381 °F; 467 K)|
|Boiling point||268 °C (514 °F; 541 K)|
|Solubility||soluble in dry ether, dry alcohol, organic solvents|
|Main hazards||oxidizer, hydrolyzes to release HCl|
Related molybdenum chlorides
Except where otherwise noted, 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 moisture-sensitive and soluble in chlorinated solvents. Usually called molybdenum pentachloride, it is in fact 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, which in turn reacts with THF to give MoCl4(THF)2, a precursor to other molybdenum-containing complexes. 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.
- J. Beck and F. Wolf "Three New Polymorphic Forms of Molybdenum Pentachloride" Acta Cryst. 1997, vol. B53, pp.895-903.doi:10.1107/S0108768197008331
- Wells, A. E (1984). Structural Inorganic Chemistry, 5th ed. Oxford: Clarendon Press.
- Brunvoll, J., Ischenko, A. A., Spiridonov, V. P. & Strand, T. G. Acta Chem. Scand. 1984, volume A38, pp. 115-120.
- Holleman, A. F.; Wiberg, E. "Inorganic Chemistry" Academic Press: San Diego, 2001. ISBN 0-12-352651-5.
- Dilworth, J. R.; Richards, R. L. "The Synthesis of Molybdenum and Tungsten Dinitrogen Compounds" Inorganic Syntheses, 1990, volume 28, pages 33-45. ISBN 0-471-52619-3.
- Calderazzo, F.; Maichle-Mössmer, C.; Pampaloni, G.; Strähle, J. "Low-temperature Syntheses of Vanadium(III) and Molybdenum(IV) Bromides by Halide Exchange", Journal of the Chemical Society, Dalton Transactions, 1993, pages 655-8.doi:10.1039/DT9930000655
- T. Kauffmann, S. Torii, T. Inokuchi “Molybdenum(V) Chloride” in Encyclopedia of Reagents for Organic Synthesis 2004, J. Wiley & Sons, New York. doi:10.1002/047084289.