Cyclobutadieneiron tricarbonyl

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Cyclobutadieneiron tricarbonyl
Cyclobutadiene-iron-tricarbonyl-from-xtal-3D-balls.png
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
Appearancepale 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]

Contents

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

Oxidative decomplexation of cyclobutadiene is achieved by treating the tricarbonyl complex with ceric ammonium nitrate. The released cyclobutadiene is trapped with a quinone, which functions as a dienophile. [5]

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

CyclobutadieneirontricarbonylReactions.png

It undergoes Friedel-Crafts acylation with acetyl chloride and aluminium chloride to give the acyl derivative 2, with formaldehyde and hydrochloric acid to the chloromethyl derivative 3, in a Vilsmeier-Haack reaction with N-methylformanilide and phosphorus oxychloride to the formyl 4, and in a Mannich reaction to amine derivative 5.

The reaction mechanism is identical to that of EAS:

Cyclobutadieneirontricarbonylreactionmechanism.png

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 is a case of theory before experiment. [10]

Related Research Articles

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Organosodium chemistry is the chemistry of organometallic compounds containing a carbon to sodium chemical bond. The application of organosodium compounds in chemistry is limited in part due to competition from organolithium compounds, which are commercially available and exhibit more convenient reactivity.

<span class="mw-page-title-main">Organomolybdenum chemistry</span> Chemistry of compounds with Mo-C bonds

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<span class="mw-page-title-main">Rowland Pettit</span>

Rowland Pettit was an Australian-born American chemist. He was awarded an overseas scholarship from the Royal Commission 1851 from 1952 - 1954. He came to London to Queen Mary College to conduct research into "the molecular orbital theory of organic chemistry and its application". Pettit was noted for preparation of Cyclobutadieneiron tricarbonyl and the related trimethylenemethane complex. Pettit was head of the Department of Chemistry and W. T. Doherty Professor in Chemistry at the University of Texas, Austin, a member of the National Academy of Sciences, a member of the American Chemical Society, a member of the Chemical Society of London, a recipient of the American Chemical Society's the Southwest Regional Award, a member of the American Academy of Arts and Sciences.

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References

  1. Seyferth, Dietmar (2003). "(Cyclobutadiene)iron Tricarbonyl. A Case of Theory before Experiment". Organometallics. 22: 2–20. doi:10.1021/om020946c.
  2. Cyclobutadiene- and Benzocyclobutadiene-Iron Tricarbonyl Complexes G. F. Emerson, L. Watts, R. Pettit; J. Am. Chem. Soc.; 1965; 87(1); 131-133. doi : 10.1021/ja01079a032
  3. Pettit, R.; Henery, J. (1970). "Cyclobutadieneiron Tricarbonyl". Organic Syntheses. 50: 21. doi:10.15227/orgsyn.050.0021.
  4. P. D. Harvey; W. P. Schaefer; H. B. Gray; D. F. R. Gilson; I. S. Butler (1988). "Structure of tricarbonyl(η4-cyclobutadienyl)iron(0) at −45 °C". Inorg. Chem. 27 (1): 57–59. doi:10.1021/ic00274a013.
  5. L. Brener; J. S. Mckennis; R. Pettit (1976). "Cyclobutadiene In Synthesis: endo-Tricyclo[4.4.0.02,5]deca-3,8-diene-7,10-dione". Org. Synth. 55: 43. doi:10.15227/orgsyn.055.0043.
  6. Cyclobutadieneiron Tricarbonyl. A New Aromatic System J. D. Fitzpatrick, L. Watts, G. F. Emerson, R. Pettit J. Am. Chem. Soc.; 1965, vol. 87, 3254-3255 doi : 10.1021/ja01092a050
  7. R. P. Dodge, V. Schomaker, "Crystal Structure of Tetraphenylcyclobutadiene Iron Tricarbonyl", Nature 1960, vol. 186, 798-799. doi : 10.1038/186798b0
  8. Longuet-Higgins, H. C.; Orgel, L. E. (1956-01-01). "385. The possible existence of transition-metal complexes of cyclobutadiene". Journal of the Chemical Society (Resumed): 1969–1972. doi:10.1039/JR9560001969. ISSN   0368-1769.
  9. Criegee, R.; Schröder, G. (1959-01-21). "Ein Nickel-Komplex des Tetramethyl-Cyclobutadiens". Angewandte Chemie (in German). 71 (2): 70–71. doi:10.1002/ange.19590710210.
  10. Seyferth, Dietmar (2003-01-01). "(Cyclobutadiene)iron TricarbonylA Case of Theory before Experiment". Organometallics. 22 (1): 2–20. doi:10.1021/om020946c. ISSN   0276-7333.