Cyclobutadieneiron tricarbonyl

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Cyclobutadieneiron tricarbonyl
Identifiers
3D model (
JSmol
)
ChemSpider
  • InChI=1S/C4H4.3CO.Fe/c1-2-4-3-1;3*1-2;/h1-4H;;;;
    Key: PHCIVYPTULNGTJ-UHFFFAOYSA-N
  • c1ccc1.[Fe]([C]#[O])([C]#[O])[C]#[O]
Properties
C7H4FeO3
Molar mass 191.951 g·mol−1
Appearance pale yellow oil
Boiling point 47 °C (117 °F; 320 K) 3 mm
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Cyclobutadieneiron tricarbonyl is an

organoiron compound with the formula Fe(C4H4)(CO)3. It is a yellow oil that is soluble in organic solvents. It has been used in organic chemistry as a precursor for cyclobutadiene, which is an elusive species in the free state.[1]

Preparation and structure

Cyclobutadieneiron tricarbonyl was first prepared in 1965 by Pettit from 3,4-dichlorocyclobutene and diiron nonacarbonyl:[2][3]

C4H4Cl2 + 2 Fe2(CO)9 → (C4H4)Fe(CO)3 + 2 Fe(CO)5 + 5 CO + FeCl2

The compound is an example of a

piano stool complex. The C-C distances are 1.426 Å.[4]

Properties

dienophile.[5]

Cyclobutadieneiron tricarbonyl displays aromaticity as evidenced by some of its reactions, which can be classified as electrophilic aromatic substitution:[6]

Cyclobutadieneiron tricarbonyl Reactions

It undergoes

formyl 4, and in a Mannich reaction
to amine derivative 5.

The reaction mechanism is identical to that of EAS:

Cyclobutadieneiron tricarbonyl EAS reactionmechanism

Related compounds

Several years before Petit's work, (C4Ph4)Fe(CO)3 had been prepared from the reaction of iron carbonyl and diphenylacetylene.[7]

(Butadiene)iron tricarbonyl is isoelectronic with cyclobutadieneiron tricarbonyl.

History

In 1956, Longuet-Higgins and Orgel[8] predicted the existence of transition-metal cyclobutadiene complexes, in which the degenerate eg orbital of cyclobutadiene has the correct symmetry for π interaction with the dxz and dyz orbitals of the proper metal. The compound was synthesized three years after the prediction[9] This case of theory before experiment.[10]

References

  1. doi:10.1021/om020946c
    .
  2. J. Am. Chem. Soc.; 1965; 87(1); 131-133. First Page
  3. doi:10.15227/orgsyn.050.0021
    .
  4. doi:10.1021/ic00274a013
    .
  5. doi:10.15227/orgsyn.055.0043
    .
  6. J. Am. Chem. Soc.; 1965, vol. 87, 3254-3255 Abstract
  7. doi:10.1038/186798b0
  8. ISSN 0368-1769
    .
  9. doi:10.1002/ange.19590710210
    .
  10. ISSN 0276-7333
    .
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