Disodium tetracarbonylferrate

Disodium tetracarbonylferrate
IUPAC name

disodium tetracarbonylferrate
Systematic name

disodium tetracarbonylferrate
Other names

disodium iron tetracarbonyl, Collman's reagent
Identifiers
CAS number 14878-31-0
Properties
Molecular formula C4FeNa2O4
Molar mass 213.87
Appearance Colorless solid
Density 2.16 g/cm3, solid
Solubility in water Decomposes
Solubility tetrahydrofuran, dimethylformamide, dioxane
Structure
Crystal structure Distorted tetrahedron
Coordination
geometry		 Tetrahedral
Hazards
Main hazards Pyrophoric
Related compounds
Related compounds Iron pentacarbonyl
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Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Disodium tetracarbonylferrate is the chemical 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]

Contents

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

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] + X2 → RC(O)X + FeX2 + 3 CO + NaCl

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. ^ a b Strong, H.; Krusic, P. J.; San Filippo, J. (1990). Robert J. Angelici. ed. "Sodium Carbonyl Ferrate, Na2Fe(CO)], Na2[Fe2(CO)8], and Na2[Fe3(CO)11]. Bis[μ-Nitrido-Bis(triphenylphosphorus)(1+] Undecarcarbonyltriferrate(2-), [(Ph3P)2N]2[Fe3(CO)11]". Inorganic Syntheses. Inorganic Syntheses (New York: J. Wiley & Sons) 28: 203–207. doi:10.1002/9780470132593.ch52. ISBN 0-471-52619-3. 
  2. ^ Pike, Robert D., (2001). Disodium Tetracarbonylferrate (II-). Encyclopedia of Reagents for Organic Synthesis.
  3. ^ Miessler, G. L., Tarr, D. A. (2004). Inorganic chemistry. Upper Saddle River,New Jersey: Pearson Publication.
  4. ^ H. B. Chin, R. Bau (1976). "The Crystal Structure of Disodium Tetracarbonylferrate. Distortion of the Tetracarbonylferrate(2-) Anion in the Solid State". J. Am. Chem. Soc. 98 (9): 2434–2439. doi:10.1021/ja00425a009. 
  5. ^ a b M. P. Cooke (1970). "Facile conversion of alkyl bromides into aldehydes using sodium tetracarbonylferrate(-II)". J. Am. Chem. Soc. 92 (20): 6080–6082. doi:10.1021/ja00723a056. 

Further reading