Molybdenum(V) chloride 4753858 206690692 2008-04-19T14:04:48Z AlphaEta 2368277 image redlinked {{Chembox new | Name = Molybdenum(V) chloride | ImageFile = <!-- Molybdenum(V) chloride.jpg --> <!-- | ImageSize = 200px --> | ImageName = Molybdenum(V) chloride | IUPACName = Molybdenum(V) chloride | OtherNames = Molybdenum pentachloride | Section1 = {{Chembox Identifiers | SMILES = | CASNo = 10241-05-1 | RTECS = QA4690000 }} | Section2 = {{Chembox Properties | Formula = MoCl<sub>5</sub> | MolarMass = 273.21 g/mol | Appearance = dark-green<br />moisture sensitive | Density = 2.928 g/cm<sup>3</sup> | Solubility = hydrolyzes | Solvent = other solvents | SolubleOther = chlorocarbons<br />benzene | MeltingPt = 194 °C | BoilingPt = 268 °C }} | Section3 = {{Chembox Structure | Coordination = edge-shared bioctahedron | CrystalStruct = | Dipole = }} | Section7 = {{Chembox Hazards | ExternalMSDS = | MainHazards = oxidizer, hydrolyzes to release HCl | RPhrases = 29-34 | SPhrases = 26-36/37/39-43-45 }} | Section8 = {{Chembox Related | OtherCpds = [[titanium tetrachloride]]<br /> [[chromyl chloride]] }} }} '''Molybdenum pentachloride''' is the chemical compound with the formula MoCl<sub>5</sub>. This dark volatile solid is an important starting reagent in the preparation of molybdenum compounds. In the solid state molybdenum pentachloride exists as a dimer with the formula Mo<sub>2</sub>Cl<sub>10</sub>, with a structure similar to that of the corresponding Nb and Ta pentachlorides. In the gas phase, it is a monomeric pentahalide. It is paramagnetic, with one unpaired electron per Mo center, reflecting the fact that the formal oxidation state is 5+, leaving one valence electron. ==Preparation and properties== MoCl<sub>5</sub> is prepared by chlorination of Mo metal but also chlorination of MoO<sub>3</sub>. Notice that MoCl<sub>6</sub> ''cannot'' be prepared under normal conditions. In contrast, the heavier analogues WCl<sub>6</sub> is well known. MoCl<sub>5</sub> is a strong oxidant, as indicated by its non-reactivity toward Cl<sub>2</sub>. It is easily reduced by even MeCN to afford the adduct MoCl<sub>4</sub>(MeCN)<sub>2</sub>, which in turn reacts with [[THF]] to give MoCl<sub>4</sub>(THF)<sub>2</sub>, a very versatile reagent in the chemistry of molybdenum. MoCl<sub>5</sub> is reduced by HBr to form MoBr<sub>4</sub>. The reaction is conducted in ethylbromide at -50 C: :: 2 MCl<sub>5</sub> + 10 HBr → 2 MoBr<sub>4</sub> + 10 HCl + Br<sub>2</sub> MoBr<sub>4</sub> reacts with THF to give the Mo(III) species mer-MoBr<sub>3</sub>(THF)<sub>3</sub>. MoCl<sub>5</sub> is a good Lewis acid toward non-oxidizable ligands. It forms an adduct with chloride to form [MoCl<sub>6</sub>]<sup>-</sup>. ==Safety considerations== MoCl<sub>5</sub> is an aggressive oxidant and readily hydrolyzes to release HCl. ==References== {{Citationstyle|date=September 2007}} {{reflist}} *T. Kauffmann, S. Torii, T. Inokuchi “Molybdenum(V) Chloride” in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. DOI: 10.1002/047084289. *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-Mossmer, C.; Pampaloni, G. and 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. [[Category:Molybdenum compounds]] [[Category:Chlorides]] [[Category:Metal halides]]