|Systematic IUPAC name
3D model (JSmol)
CompTox Dashboard (EPA)
|Appearance||Vivid, white, translucent crystals|
|Density||1.96 g cm-3|
|Melting point||150 °C (302 °F; 423 K)|
|Boiling point||156 °C (313 °F; 429 K)|
Std enthalpy of
|-989.1 kJ mol-1|
Std enthalpy of
|-2123.4 kJ mol-1|
|Safety data sheet||External MSDS|
|S-phrases (outdated)||(S1/2), S36/37/39, S45|
|NFPA 704 (fire diamond)|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Molybdenum hexacarbonyl (also called molybdenum carbonyl) is the chemical compound with the formula Mo(CO)6. This colorless solid, like its chromium and tungsten analogues, is noteworthy as a volatile, air-stable derivative of a metal in its zero oxidation state.
Mo(CO)6 adopts an octahedral geometry consisting of six rod-like CO ligands radiating from the central Mo atom. A recurring minor debate in some chemical circles concerns the definition of an "organometallic" compound. Usually, organometallic indicates the presence of a metal directly bonded via a M-C bond to an organic fragment, which must in turn have a C-H bond. By this strict definition, Mo(CO)6 is not organometallic.
Mo(CO)6 is prepared by the reduction of molybdenum chlorides or oxides under a pressure of carbon monoxide, although it would be unusual to prepare this inexpensive compound in the laboratory. The compound is somewhat air-stable and sparingly soluble in nonpolar organic solvents.
Mo(CO)6 is a popular reagent in organometallic synthesis because one or more CO ligands can be displaced by other donor ligands. Mo(CO)6, [Mo(CO)3(MeCN)3], and related derivatives are employed as catalysts in organic synthesis for example, alkyne metathesis and the Pauson-Khand reaction.
The thermal reaction of Mo(CO)6 with piperidine affords Mo(CO)4(piperidine)2. The two piperidine ligands in this yellow-colored compound are labile, which allows other ligands to be introduced under mild conditions. For instance, the reaction of [Mo(CO)4(piperidine)2] with triphenyl phosphine in boiling dichloromethane (b.p. ca. 40 °C) gives cis-[Mo(CO)4(PPh3)2]. This cis- complex isomerizes in toluene to trans-[Mo(CO)4(PPh3)2].
Mo(CO)6 also can be converted to its tris(acetonitrile) derivative. The compound serves as a source of "Mo(CO)3". For instance treatment with allyl chloride gives [MoCl(allyl)(CO)2(MeCN)2], whereas treatment with KTp and sodium cyclopentadienide gives [MoTp(CO)3]- and [MoCp(CO)3]- anions, respectively. These anions react with a variety of electrophiles. A related source of Mo(CO)3 is cycloheptatrienemolybdenum tricarbonyl.
Like all metal carbonyls, Mo(CO)6 is dangerous source of volatile metal as well as CO.