Disodium tetracarbonylferrate

Structure

The dianion [Fe(CO)4]2− is isoelectronic with Ni(CO)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. Modern synthesis use sodium naphthalene or sodium benzophenone ketyls as the reducants: :Fe(CO)5 + 2 Na → Na2[Fe(CO)4] + CO

When a deficiency of sodium is used, the reduction affords deep yellow octacarbonyl diferrate: :2 Fe(CO)5 + 2 Na → Na2[Fe2(CO)8] + 2 CO Some specialized methods do not start with iron carbonyl.

Reactions

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

3(C(O)R)]Na, then R'X can be added to form RC(O)R'.

:Na[RFe(CO)4] + L → [LFe(CO)3(C(O)R)]Na → RC(O)R' + [LFe(CO)3]Na--

References

References

1. (1990). "Inorganic Syntheses".
2. (2004). "Inorganic Chemistry". Pearson.
3. (1976). "The Crystal Structure of Disodium Tetracarbonylferrate. Distortion of the Tetracarbonylferrate²⁻ Anion in the Solid State". [[Journal of the American Chemical Society]].
4. (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.
5. Cooke, M. P.. (1970). "Facile Conversion of Alkyl Bromides into Aldehydes Using Sodium Tetracarbonylferrate(-II)". [[Journal of the American Chemical Society]].
6. Richard G. Finke, Thomas N. Sorrell. (1979). "Nucleophilic Acylation with Disodium Tetracarbonylferrate: Methyl 7-Oxoheptanoate and Methyl 7-Oxoöctanoate". Organic Syntheses.
7. Scholsser, M.. (2013). "Organometallics in Synthesis, Third Manual". Wiley.
8. Pike, R. D.. (2001). "Disodium Tetracarbonylferrate(-II)".