Diiron nonacarbonyl

Diiron nonacarbonyl
Names
IUPAC name
Diiron nonacarbonyl, tri-μ-carbonyl-bis(tricarbonyliron)(Fe—Fe)
Other names
Iron enneacarbonyl
Identifiers
15321-51-4 Yes
ChemSpider 4807522 Yes
Jmol-3D images Image
Properties
Fe2C9O9
Molar mass 363.78 g/mol
Appearance orange crystals
Density 2.08 g/cm3
Melting point decomposes at 100 °C
Boiling point decomposes
insoluble
Structure
Dipole moment 0 D
Hazards
Main hazards Toxic
Related compounds
Related iron carbonyls
Iron pentacarbonyl
Triiron dodecacarbonyl
Related compounds
 Dimanganese decacarbonyl
Dicobalt octacarbonyl
Except where noted otherwise, data is given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 Yes verify (what is: Yes/?)
Infobox references

Diiron nonacarbonyl is an inorganic compound with the formula Fe2(CO)9. This metal carbonyl is an important reagent in organometallic chemistry and of occasional use in organic synthesis.[1] It is a more reactive source of Fe(0) than Fe(CO)5 and less dangerous to handle because it is nonvolatile. This micaceous orange solid is virtually insoluble in all common solvents.

Synthesis and structure

Following the original method,[2] photolysis of an acetic acid solution of Fe(CO)5 produces Fe2(CO)9 in good yield:[3][4]

2 Fe(CO)5 → Fe2(CO)9 + CO

Fe2(CO)9 consists of a pair of Fe(CO)3 centers linked by three bridging CO ligands. Although older textbooks show an Fe-Fe bond, theoretical analyses have consistently indicated the absence of a direct Fe-Fe bond.[5] The minor isomer has been crystallized together with C60 The iron atoms are equivalent and octahedral molecular geometry. Elucidation of the structure of Fe2(CO)9 proved to be challenging because its low solubility inhibits growth of crystals. The Mößbauer spectrum reveals one quadrupole doublet, consistent with the D3h-symmetric structure.

Reactions

Fe2(CO)9 is a precursor to compounds of the type Fe(CO)4L and Fe(CO)3(diene). Such syntheses are typically conducted in THF solution. In these conversions, it is proposed that small amounts of Fe2(CO)9 dissolve according the following reaction:[6]

Fe2(CO)9 → Fe(CO)5 + Fe(CO)4(THF)

Cyclobutadieneiron tricarbonyl is prepared using Fe2(CO)9. Fe2(CO)9 has also been employed in the synthesis of cyclopentadienones via a net [2+3]-cycloaddition from dibromoketones, known as the Noyori [3+2] reaction.[7]

Low temperature UV/vis photolysis of Fe2(CO)9 yields the Fe2(CO)8 unsaturated complex, producing both CO-bridged and unbridged isomers. [8]

References

  1. ↑ Elschenbroich, C.; Salzer, A. ”Organometallics : A Concise Introduction” (2nd Ed) (1992) Wiley-VCH: Weinheim. ISBN 3-527-28165-7
  2. ↑ Edmund Speyer; Hans Wolf (1924). "Über die Bildungsweise von Eisen-nonacarbonyl aus Eisen-pentacarbonyl". Berichte der deutschen chemischen Gesellschaft 60: 1424–1425. doi:10.1002/cber.19270600626.
  3. ↑ King, R. B. Organometallic Syntheses. Volume 1 Transition-Metal Compounds; Academic Press: New York, 1965. ISBN 0-444-42607-8.
  4. ↑ E. H. Braye, W. Hübel (1966). "Diiron Enneacarbonyl". Inorg. Synth. Inorganic Syntheses 8: 178. doi:10.1002/9780470132395.ch46. ISBN 978-0-470-13239-5.
  5. ↑ Jennifer C. Green, Malcolm L. H. Green, Gerard Parkin "The occurrence and representation of three-centre two-electron bonds in covalent inorganic compounds" Chem. Commun. 2012, 11481-11503. doi:10.1039/c2cc35304k
  6. ↑ F. Albert Cotton, Jan M. Troup "Reactivity of diiron nonacarbonyl in tetrahydrofuran. I. Isolation and characterization of pyridinetetracarbonyliron and pyrazinetetracarbonyliron" J. Am. Chem. Soc., 1974, volume 96, pp 3438–3443. doi:10.1021/ja00818a016
  7. ↑ R. Noyori, R.; Yokoyama, K.; Hayakawa, Y. (1988). "Cyclopentanones from α, α'-Dibromoketones and Enamines: 2,5-Dimethyl-3-Phenyl-2-Cyclopenten-1-one". Org. Synth.; Coll. Vol. 6, p. 520
  8. ↑ Susan C. Fletcher, Martyn Poliakoff, James J. Turner (1986). "Structure and Reactions of Fe2(CO)8: An IR Spectroscopic study using 13C Photolysis with plane-polarized light, and matrix isolation". Inorg. Chem. 25 (20): 3597. doi:10.1021/ic00240a014.