Bis(cyclooctatetraene)iron is an
organoiron compound with the formula Fe(C
8H
8)
2, abbreviated Fe(COT)
2. It is an air-sensitive black solid that is soluble in
diethyl ether
Diethyl ether, or simply ether, is an organic compound in the ether class with the formula , sometimes abbreviated as (see Pseudoelement symbols). It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable li ...
and
aromatic
In chemistry, aromaticity is a chemical property of cyclic ( ring-shaped), ''typically'' planar (flat) molecular structures with pi bonds in resonance (those containing delocalized electrons) that gives increased stability compared to satur ...
solvent
A solvent (s) (from the Latin '' solvō'', "loosen, untie, solve") is a substance that dissolves a solute, resulting in a solution. A solvent is usually a liquid but can also be a solid, a gas, or a supercritical fluid. Water is a solvent for ...
s. 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
Triethylaluminium is one of the simplest examples of an organoaluminium compound. Despite its name it has the formula Al2( C2H5)6 (abbreviated as Al2Et6 or TEA), as it exists as a dimer. This colorless liquid is pyrophoric. It is an industrially ...
in the presence of 1,3,5,7-
cyclooctatetraene
1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as nnulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of ...
:
[
:Fe(C5H7O2)3 + 2 C8H8 + 3 Al(C2H5)3 → Fe(C8H8)2 + 3 Al(C2H5)2(C5H7O2) + C2H4 + C2H6
]
Structure
According to analysis by single crystal X-ray crystallography
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...
, the two cyclooctatetraene rings bind differently to the Fe center, leading to the description Fe(''η''4-C8H8)(''η''6-C8H8). One cyclooctatetraene ring binds to Fe with two adjacent double bonds. This interaction is similar to that in (''η''4-C8H8)Fe(CO)3. 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 (''η''6-C8H8)Mo(CO)3. The non-coordinated double bond has a similar bond length as an ordinary double bond.[{{cite journal, first1=G. , last1=Allergra, first2= A., last2= Colmbo , first3=A. , last3=Immirzi , first4=I. W. , last4=Bassi , title=The Crystal Structure of Bis(cyclooctatetraene)iron, , journal=]J. Am. Chem. Soc.
The ''Journal of the American Chemical Society'' is a weekly peer-reviewed scientific journal that was established in 1879 by the American Chemical Society. The journal has absorbed two other publications in its history, the ''Journal of Analytical ...
, volume= 90, issue=16 , date=1968 , pages=4454–4456 , doi=10.1021/ja01018a046
In solution, Fe(C8H8)2 is a fluxional molecule
In chemistry and molecular physics, fluxional (or non-rigid) molecules are molecules that undergo dynamics such that some or all of their atoms interchange between symmetry-equivalent positions. Because virtually all molecules are fluxional in ...
such that its 1H NMR spectrum consists of a singlet at room-temperature.[
]
References
Organoiron compounds
Sandwich compounds
Iron(0) compounds