Disodium tetracarbonylferrate

Disodium tetracarbonylferrate is the organoiron compound with the formula Na2[Fe(CO)4]. It is always used as a solvate, e.g., with tetrahydrofuran or dimethoxyethane, which bind to the sodium cation.[1] An oxygen-sensitive colourless solid, it is a reagent in organometallic and organic chemical research. The dioxane solvated sodium salt is known as Collman's reagent, in recognition of James P. Collman, an early popularizer of its use.[2]

Disodium tetracarbonylferrate
Names
IUPAC name
disodium tetracarbonylferrate
Systematic IUPAC name
disodium tetracarbonylferrate
Other names
disodium iron tetracarbonyl, Collman's reagent
Identifiers
3D model (JSmol)
ECHA InfoCard 100.035.395
EC Number
  • 238-951-0
  • InChI=1S/4CHO.Fe.2Na/c4*1-2;;;/h4*1H;;;/q4*-1;+2;2*+1
    Key: JSMIGIAJTPRDEQ-UHFFFAOYSA-N
  • [CH-]=O.[CH-]=O.[CH-]=O.[CH-]=O.[Na+].[Na+].[Fe+2]
Properties
C4FeNa2O4
Molar mass 213.87
Appearance Colorless solid
Density 2.16 g/cm3, solid
Decomposes
Solubility tetrahydrofuran, dimethylformamide, dioxane
Structure
Distorted tetrahedron
Tetrahedral
Hazards
Occupational safety and health (OHS/OSH):
Main hazards
 Pyrophoric
Related compounds
Related compounds
 Iron pentacarbonyl
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Structure

The dianion [Fe(CO)4]2− is isoelectronic with Ni(CO)4.[3][4] The iron center is tetrahedral, with Na+---OCFe interactions. It is commonly used with dioxane complexed to the sodium cation.

Synthesis

The reagent was originally generated in situ by reducing iron pentacarbonyl with sodium amalgam.[5] Modern synthesis use sodium naphthalene or sodium benzophenone ketyls as the reducants:[1][6]

Fe(CO)5 + 2 Na → Na2[Fe(CO)4] + CO

When a deficiency of sodium is used, the reduction affords deep yellow octacarbonyl diferrate:[1]

2 Fe(CO)5 + 2 Na → Na2[Fe2(CO)8] + 2 CO

Some specialized methods do not start with iron carbonyl.[7]

Reactions

It is used to synthesise aldehydes from alkyl halides.[8] The reagent was originally described for the conversion of primary alkyl bromides to the corresponding aldehydes in a two-step, "one-pot" reaction:[5]

Na2[Fe(CO)4] + RBr → Na[RFe(CO)4] + NaBr

This solution is then treated sequentially with PPh3 and then acetic acid to give the aldehyde, RCHO.

Disodium tetracarbonylferrate can be used to convert acid chlorides to aldehydes. This reaction proceeds via the intermediacy of iron acyl complex.

Na2[Fe(CO)4] + RCOCl → Na[RC(O)Fe(CO)4] + NaCl
Na[RC(O)Fe(CO)4] + HCl → RCHO + "Fe(CO)4" + NaCl

Disodium tetracarbonylferrate reacts with alkyl halides (RX) to produce alkyl complexes:

Na2[Fe(CO)4] + RX → Na[RFe(CO)4] + NaX

Such iron alkyls can be converted to the corresponding carboxylic acid and acid halides:

Na[RFe(CO)4] + O2, H+ →→ RCO2H + Fe...
Na[RFe(CO)4] + 2 X2 → RC(O)X + FeX2 + 3 CO + NaX


References
  1. Strong, H.; Krusic, P. J.; San Filippo, J. (1990). Sodium Carbonyl Ferrates, Na2[Fe(CO)4], Na2[Fe2(CO)8], and Na2[Fe3(CO)11]. Bis[μ-Nitrido-Bis(triphenylphosphorus)1+] Undeca-Carbonyltriferrate2−, [(Ph3P)2N]2[Fe3(CO)11]. Inorganic Syntheses. Vol. 28. pp. 203–207. doi:10.1002/9780470132593.ch52. ISBN 0-471-52619-3.
  2. Miessler, G. L.; Tarr, D. A. (2004). Inorganic Chemistry. Upper Saddle River, NJ: Pearson.
  3. Chin, H. B.; Bau, R. (1976). "The Crystal Structure of Disodium Tetracarbonylferrate. Distortion of the Tetracarbonylferrate2− Anion in the Solid State". Journal of the American Chemical Society. 98 (9): 2434–2439. doi:10.1021/ja00425a009.
  4. Teller, R. G.; Finke, R. G.; Collman, J. P.; Chin, H. B.; Bau, R. (1977). "Dependence of the tetracarbonylferrate(2-) geometry on counterion: crystal structures of dipotassium tetracarbonylferrate and bis(sodium crypt) tetracarbonylferrate [crypt = N(CH2CH2OCH2CH2OCH2CH2)3N]". Journal of the American Chemical Society. 99 (4): 1104–1111. doi:10.1021/ja00446a022.
  5. Cooke, M. P. (1970). "Facile Conversion of Alkyl Bromides into Aldehydes Using Sodium Tetracarbonylferrate(-II)". Journal of the American Chemical Society. 92 (20): 6080–6082. doi:10.1021/ja00723a056.
  6. Richard G. Finke, Thomas N. Sorrell (1979). "Nucleophilic Acylation with Disodium Tetracarbonylferrate: Methyl 7-Oxoheptanoate and Methyl 7-Oxoöctanoate". Organic Syntheses. 59: 102. doi:10.15227/orgsyn.059.0102.
  7. Scholsser, M. (2013). Organometallics in Synthesis, Third Manual. Chicester, England: Wiley.
  8. Pike, R. D. (2001). "Disodium Tetracarbonylferrate(-II)". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rd465.

Further reading
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