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Transition Metal-Diene Complexes. Part 4. The Crystal and Molecular Structure and Isomerization of η-Cyclopentadienyl(η-3-methoxycarbonyl-cyclohexa-1,4-diene)rhodium(I)

DOI: 10.1039/DT9810001034

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 1034 - 1040 (1981)

Update date:2022-08-16

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Authors:

Drew, Michael G. B.Drew, Michael G. B.

Regan, Catrionia M.Regan, Catrionia M.

Nelson, S. MartinNelson, S. Martin

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Article abstract of DOI:10.1039/DT9810001034

Crystals of the title compound, , are monoclinic, space group I2/a with cell dimensions a=28.124(14), b=6.141(8), c=14.569(11) Angstroem, β=112.43(9) deg, and Z=8.The intensities of 1 325 reflections above background were collected by counter methods and refined to R 0.052.The rhodium atom is bonded to the five carbon atoms of the planar cyclopentadienyl ring and to the four olefinic carbon atoms of the cyclohexa-1,4-diene.The cyclohexa-1,4-diene ring is in the boat conformation with the two saturated carbon atoms lying 0.66, 0.70 Angstroem above the plane of the four olefinic carbons in a direction away from the metal.The carbomethoxy-subtituent is planar and occupies an axial position with respect to the cyclohexadiene boat.The title complex undergoes a kinetically controlled isomerization when heated in toluene or acid-free o-dichlorobenzene to a mixture of complexes containing co-ordinated 5-methoxy-carbonyl- (major product) and 2-methoxycarbonyl-cyclohexa-1,3-diene (minor product).In the presence of acid in o-dichlorobenzene the major product undergoes a secondary isomerization to the complex containing co-ordinated 1-methoxycarbonylcyclohexa-1,3-diene.For the primary isomerization a mechanism involving the formation of a hydro-η3-allylic intermediate is proposed in which the rate-determining step is a carbon-to-metal hydride-ion transfer.For the secondary isomerization, in the presence of acid, a reverse metal-to-carbon hydrogen transfer is believed to operate.

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Product name:2,5-Cyclohexadiene-1-carboxylic acid, methyl ester

Cas No:30889-20-4

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