Bis(cyclooctatetraene)iron

Bis(cyclooctatetraene)iron

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Identifiers
CAS Number	12184-52-0
Properties
Chemical formula	C16H16Fe
Vapor pressure	{{{value}}}
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Bis(cyclooctatetraene)iron is an organoiron compound with the formula Fe(C₈H₈)₂, abbreviated Fe(COT)₂. It is an air-sensitive black solid that is soluble in diethyl ether and aromatic solvents. The compound decomposes in solution after a few days even under inert atmosphere. It has no known practical applications but has been studied as a soluble source of Fe(0).

Preparation

The laboratory synthesis of Fe(COT)₂, using Schlenk techniques, involves reduction of ferric acetylacetonate by triethylaluminium in the presence of 1,3,5,7-cyclooctatetraene:

Fe(C₅H₇O₂)₃ + 2 C₈H₈ + 3 Al(C₂H₅)₃ → Fe(C₈H₈)₂ + 3 Al(C₂H₅)₂(C₅H₇O₂) + ​³⁄₂ C₂H₄ + ​³⁄₂ C₂H₆

Structure

According to analysis by single crystal X-ray crystallography, the two cyclooctatetraene rings bind differently to the Fe center, leading to the description Fe(η⁴-C₈H₈)(η⁶-C₈H₈) One cyclooctatetraene ring binds to Fe with two adjacent double bonds. This interaction is similar to that in (η⁴-C₈H₈)Fe(CO)₃. The two planar groups formed by carbons 1,2,7,8 and carbons 3,4,5,6,7 form a dihedral angle of 33°. The second cyclooctatetraene ring binds through three double bonds. The shape and coordination of the lower ring is similar to that in (η⁶-C₈H₈)Mo(CO)₃. The non-coordinated double bond has a similar bond length as an ordinary double bond.

In solution, Fe(C₈H₈)₂ is a fluxional molecule such that the room-temperature ¹H NMR spectrum consists of a singlet.