(Mesitylene)molybdenum tricarbonyl is an

organomolybdenum compound Organomolybdenum chemistry is the chemistry of chemical compounds with Mo-C bonds. The heavier group 6 elements molybdenum and tungsten form organometallic compounds similar to those in organochromium chemistry but higher oxidation states tend to ...

derived from the aromatic compound

mesitylene Mesitylene or 1,3,5-trimethylbenzene is a derivative of benzene with three methyl substituents positioned symmetrically around the ring. The other two isomeric trimethylbenzenes are 1,2,4-trimethylbenzene (pseudocumene) and 1,2,3-trimethylbenze ...

(1,3,5-trimethylbenzene) and molybdenum carbonyl. It exists as pale yellow crystals, which are soluble in organic solvents but decompose when in solution. It has been examined as a catalyst and reagent.

Synthesis

(Mesitylene)molybdenum tricarbonyl arises from the reaction of molybdenum hexacarbonyl with hot

: :Mo(CO) + (CH)CH → Mo(CO) CH)CH+ 3 CO It can also be synthesized, with good yields by displacement of

pyridine Pyridine is a basic (chemistry), basic heterocyclic compound, heterocyclic organic compound with the chemical formula . It is structurally related to benzene, with one methine group replaced by a nitrogen atom . It is a highly flammable, weak ...

ligands of the trispyridine complex Mo(CO)(pyridine) in the presence of

Lewis acid A Lewis acid (named for the American physical chemist Gilbert N. Lewis) is a chemical species that contains an empty orbital which is capable of accepting an electron pair from a Lewis base to form a Lewis adduct. A Lewis base, then, is any ...

s. This reaction proceeds at lower temperatures of the compound than the direct method :PyMo(CO) + (CH)CH + 3BF·O(CH) → CH)CHo(CO) + 3PyBF

Structure and properties

The mesitylene group is bonded to the molybdenum centre through delocalized π - electron ring. The aromaticity of the ligand is indicated by its ability to undergo Friedel-Crafts reactions, e.g. with

acetyl chloride Acetyl chloride () is an acyl chloride derived from acetic acid (). It belongs to the class of organic compounds called acid halides. It is a colorless, corrosive, volatile liquid. Its formula is commonly abbreviated to AcCl. Synthesis On an ...

. Such reactions are slower on the tricarbonyl(mesitylene)molybdenum than benzene, which suggests that the electron density contributes to the bonding to the molybdenum. The tricarbonyl(mesitylene)molybdenum complex adopts a near C symmetry with the three carbonyl groups occupying an eclipsed arrangement relative to the three methyl groups. The mesityl group is η to the molybdenum central metal atom, which lies 0.009 Å away from the ring centre and the methyl groups on the benzene are bent out of plane by 0.035 Å due to steric interaction with the carbonyl groups.

Reactions

The arene can be displaced by the

trimethylphosphite Trimethyl phosphite is an organophosphorus compound with the formula P(OCH3)3, often abbreviated P(OMe)3. It is a colorless liquid with a highly pungent odor. It is the simplest phosphite ester and finds used as a ligand in organometallic chemi ...

via a S2 type mechanism to give the ''fac''-tricarbonyltris(trimethyl phosphite)molybdenum. :(CHO)P + CH)CHo(CO) → ''fac''- CHO)Po(CO) + (CH)CH The tricarbonyl(mesitylene)molybdenum complex can be used an electron donor. Tricarbonyl(mesitylene)molybdenum can act as a catalyst for the polymerisation of

phenylacetylene Phenylacetylene is an alkyne hydrocarbon containing a phenyl group. It exists as a colorless, viscous liquid. In research, it is sometimes used as an analog for acetylene; being a liquid, it is easier to handle than acetylene gas. Preparation In ...

. The Molybdenum complex is activated with an oxidant such as

chloranil Chloranil is a quinone with the molecular formula C6Cl4O2. Also known as tetrachloro-1,4-benzoquinone, it is a yellow solid. Like the parent benzoquinone, chloranil is a planar molecule J.-M. Lü, S. V. Rosokha, I. S. Neretin and J. K. Kochi, "Qui ...

. The result of the charge transfer facilitates ring slippage and the mesitylene group changes from η to η this allows the phenylacetylene monomer units to bind to the metal centre. Recently, it has been reported that tricarbonyl(mesitylene)molybdenum can act as a catalyst for the

epoxidation In organic chemistry, an epoxide is a cyclic ether, where the ether forms a three-atom ring: two atoms of carbon and one atom of oxygen. This triangular structure has substantial ring strain, making epoxides highly reactive, more so than other ...

alkenes In organic chemistry, an alkene, or olefin, is a hydrocarbon containing a carbon–carbon double bond. The double bond may be internal or at the terminal position. Terminal alkenes are also known as Alpha-olefin, α-olefins. The Internationa ...

References

{{DEFAULTSORT:Mesitylene)Molybdenum Tricarbonyl Organomolybdenum compounds Carbonyl complexes Molybdenum(0) compounds