Diiron nonacarbonyl

Diiron nonacarbonyl
IUPAC name Diiron nonacarbonyl, tri-μ-carbonyl-bis(tricarbonyliron)(Fe—Fe)
Other names Iron enneacarbonyl
Identifiers
CAS number	15321-51-4 Y
ChemSpider	4807522 Y
Jmol-3D images	Image 1
SMILES [Fe].[Fe].[C-]#[O+].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-].[O+]#[C-]
InChI InChI=1S/9CO.2Fe/c9*1-2;; Y Key: JCXLZXJCZPKTBW-UHFFFAOYSA-N Y InChI=1/9CO.2Fe/c9*1-2;; Key: JCXLZXJCZPKTBW-UHFFFAOYAN
Properties
Molecular formula	Fe2C9O9
Molar mass	363.78 g/mol
Appearance	orange crystals
Density	2.08 g/cm3
Melting point	decomposes at 100 °C
Boiling point	decomposes
Solubility in water	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
Y nonacarbonyl (verify) (what is: Y/N?) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
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. 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 D_3h-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:^[5]

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.^[6]

Low temperature UV/vis photolysis of Fe₂(CO)₉ yields the Fe₂(CO)₈ unsaturated complex, producing both CO-bridged and unbridged isomers. ^[7]

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 "Über die Bildungsweise von Eisen-nonacarbonyl aus Eisen-pentacarbonyl" Berichte der deutschen chemischen Gesellschaft, 1924 volume 60, p. 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 9780470132395. 
5. ^ 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
6. ^ 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., http://www.orgsyn.org/orgsyn/orgsyn/prepContent.asp?prep=cv6p0520 ; Coll. Vol. 6: 520 
7. ^ 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.