Disodium tetracarbonylferrate

Disodium tetracarbonylferrate
Names
IUPAC name
disodium tetracarbonylferrate
Systematic IUPAC name
disodium tetracarbonylferrate
Other names
disodium iron tetracarbonyl, Collman's reagent
Identifiers
ECHA InfoCard 100.035.395
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
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

Disodium tetracarbonylferrate is the organometallic compound with the formula Na2[Fe(CO)4]. This oxygen-sensitive colourless solid is employed in organic synthesis,[1] mainly to synthesise aldehydes.[2] It is commonly used with dioxane complexed to the sodium cation, this dioxane solvate being known as Collman's reagent.[3] The tetracarbonylferrate dianion is tetrahedral.[4]

Synthesis

The reagent was reported by Cooke in 1970.[5] The current synthesis entails the reduction of a solution of iron pentacarbonyl in tetrahydrofuran by sodium naphthenide. The efficiency of the synthesis depends on the quality of the iron pentacarbonyl.[1]

Fe(CO)5 + 2 Na → Na2[Fe(CO)4] + CO

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

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

Other synthesis forms to make Collman's Reagent from Fe(CO)5 are listed below.

Fe(CO)5 + Na-Hg +THF → Na2[Fe(CO)4]
Fe(CO)5 + Na + Dioxane + PhCOPh → Na2[Fe(CO)4]
Fe(CO)5 + Na/PhCOPh + THF → Na2[Fe(CO)4]

Another way to synthesize Collman's Reagent is to use FeCl3.[6]

FeCl3 + Na(C10H8) + 4CO + THF → +Na → Na2[Fe(CO)4]

These synthesis pathways are extremely useful in preparing Collman's Reagent if the typical reagents to make it are not available.[7]

Reactions

The reagent was originally described for the conversion of primary alkyl bromides, RBr, 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. As for Cooke’s early discovery, an iron acyl complex undergoes protonolysis to give the aldehyde.

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


One attraction of these methods is the low cost of the iron carbonyl as well as the fact that the procedures are relatively “green” because the side product is iron-based.

References

  1. 1 2 3 Strong, H.; Krusic, P. J.; San Filippo, J. (1990). R. J. Angelici, ed. "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. New York: J. Wiley & Sons. 28: 203–207. ISBN 0-471-52619-3. doi:10.1002/9780470132593.ch52.
  2. ↑ Pike, R. D. (2001). "Disodium Tetracarbonylferrate(-II)". Encyclopedia of Reagents for Organic Synthesis. doi:10.1002/047084289X.rd465.
  3. ↑ Miessler, G. L.; Tarr, D. A. (2004). Inorganic Chemistry. Upper Saddle River, NJ: Pearson.
  4. ↑ 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.
  5. 1 2 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. ↑ Scholsser, M. (2013). Organometallics in Synthesis, Third Manual. Chicester, England: Wiley.
  7. ↑ Rameshkumar, C. (2011). New Reactive Iron Carbonyl Reagents for Applications in Organic Synthesis. Hyderabad, India: University of Hyderabad.

Further reading

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