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.
|Systematic IUPAC name
3D model (JSmol)
|Molar mass||264.01 g·mol−1|
|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|S-phrases (outdated)||(S1/2), S36/37/39, S45|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
|what is ?)(|
Structure and propertiesEdit
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.
Intermediate in inorganic and organometallic synthesisEdit
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.
UV-photolysis of a THF solution of Mo(CO)6 gives Mo(CO)5(THF). This complex is useful for the selective preparation of many monosubstituted derivatives.
Chelating ligands can be installed by direct reaction with Mo(CO)6. For example, Mo(CO)6 reacts with 2,2′-bipyridine to afford Mo(CO)4(bipy).
In many cases, sources of Mo(CO)4 are sought. For example, the two piperidine ligands in this yellow-colored compound Mo(CO)4(piperidine)2 are labile, which allows other ligands to be introduced under mild conditions. This bis(piperidine) complex is produced by the thermal reaction of Mo(CO)6 with piperidine. Reaction of [Mo(CO)4(piperidine)2] with triphenyl phosphine gives cis-[Mo(CO)4(PPh3)2]. This cis- complex isomerizes in toluene to trans-[Mo(CO)4(PPh3)2]. A related disubstituted derivative is (norbornadiene)molybdenum tetracarbonyl.
Upon heating in acetonitrile solution, Mo(CO)6 converts to the tris(acetonitrile) derivative. The compound serves as a source of "Mo(CO)3". It reacts 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.
Source of Mo atomsEdit
Safety and handlingEdit
Like all metal carbonyls, Mo(CO)6 is dangerous source of volatile metal as well as CO. Can be fatal if on skin or swallowed. It diffuses readily into plastic stoppers.
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-  Ereztech SDS]
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