Bis(cyclooctatetraene)iron
Bisiron is an organoiron compound with the formula Fe2, abbreviated Fe2. 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.
Preparation
The laboratory synthesis of Fe2, using Schlenk techniques, involves reduction of ferric acetylacetonate by triethylaluminium in the presence of 1,3,5,7-cyclooctatetraene: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. One cyclooctatetraene ring binds to Fe with two adjacent double bonds. This interaction is similar to that in Fe3. The two planar groups formed by carbon atoms 1,2,7,8 and carbon atoms 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 Mo3. The non-coordinated double bond has a similar bond length as an ordinary double bond.In solution, Fe2 is a fluxional molecule such that its 1H NMR spectrum consists of a singlet at room-temperature.