Disodium tetracarbonylferrate explained
Disodium tetracarbonylferrate is the organoiron compound with the formula Na2[Fe(CO)<sub>4</sub>]. 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]
Structure
The dianion [Fe(CO)<sub>4</sub>]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)<sub>4</sub>] + CO
When a deficiency of sodium is used, the reduction affords deep yellow octacarbonyl diferrate:[1]
2 Fe(CO)5 + 2 Na → Na2[Fe<sub>2</sub>(CO)<sub>8</sub>] + 2 COSome 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)<sub>4</sub>] + RBr → Na[RFe(CO)<sub>4</sub>] + NaBrThis 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)<sub>4</sub>] + RCOCl → Na[RC(O)Fe(CO)<sub>4</sub>] + NaCl
Na[RC(O)Fe(CO)<sub>4</sub>] + HCl → RCHO + "Fe(CO)4" + NaCl
Disodium tetracarbonylferrate reacts with alkyl halides (RX) to produce alkyl complexes:
Na2[Fe(CO)<sub>4</sub>] + RX → Na[RFe(CO)<sub>4</sub>] + NaX Such iron alkyls can be converted to the corresponding carboxylic acid and acid halides:
Na[RFe(CO)<sub>4</sub>] + O2, H+ →→ RCO2H + Fe...
Na[RFe(CO)<sub>4</sub>] + 2 X2 → RC(O)X + FeX2 + 3 CO + NaX
Further reading
- Collman, J. P. . Disodium Tetracarbonylferrate, a Transition Metal Analog of a Grignard Reagent . . 1975 . 8 . 10 . 342–347 . 10.1021/ar50094a004 .
- Ungurenasu, C. . Cotzur, C. . Disodium Tetracarbonylferrate: A Reagent for Acid Functionalization of Halogenated Polymers . . 1982 . 6 . 5–6 . 299–303 . 10.1007/BF00255401 . 101154955 .
- Hieber, V. W. . Braun, G. . Notizen: "Rheniumcarbonylwasserstoff" und Methylpentacarbonylrhenium. Zeitschrift für Naturforschung B . 1959 . 14 . 2 . 132–133 . 10.1515/znb-1959-0214. 94402946 . free .
Notes and References
- Book: Strong, H.. Krusic, P. J. . San Filippo, J. . Sodium Carbonyl Ferrates, Na2[Fe(CO)<sub>4</sub>], Na2[Fe<sub>2</sub>(CO)<sub>8</sub>], and Na2[Fe<sub>3</sub>(CO)<sub>11</sub>]. Bis[μ-Nitrido-Bis(triphenylphosphorus)<sup>1+</sup>] Undeca-Carbonyltriferrate2−, [(Ph<sub>3</sub>P)<sub>2</sub>N]2[Fe<sub>3</sub>(CO)<sub>11</sub>] . . 1990 . 28 . 203–207 . 0-471-52619-3 . 10.1002/9780470132593.ch52.
- Book: Miessler, G. L. . Tarr, D. A. . 2004 . Inorganic Chemistry . registration . Upper Saddle River, NJ . Pearson.
- Chin, H. B. . Bau, R. . The Crystal Structure of Disodium Tetracarbonylferrate. Distortion of the Tetracarbonylferrate2− Anion in the Solid State . . 1976 . 98 . 9 . 2434–2439 . 10.1021/ja00425a009 .
- Teller, R. G. . Finke, R. G. . Collman, J. P. . Chin, H. B. . Bau, R. . Dependence of the tetracarbonylferrate(2-) geometry on counterion: crystal structures of dipotassium tetracarbonylferrate and bis(sodium crypt) tetracarbonylferrate [crypt = N(CH<sub>2</sub>CH<sub>2</sub>OCH<sub>2</sub>CH<sub>2</sub>OCH<sub>2</sub>CH<sub>2</sub>)<sub>3</sub>N]. Journal of the American Chemical Society. 1977. 99. 4. 1104–1111. 10.1021/ja00446a022.
- Cooke, M. P. . Facile Conversion of Alkyl Bromides into Aldehydes Using Sodium Tetracarbonylferrate(-II) . . 1970 . 92 . 20 . 6080–6082 . 10.1021/ja00723a056 .
- Richard G. Finke, Thomas N. Sorrell. 10.15227/orgsyn.059.0102. Nucleophilic Acylation with Disodium Tetracarbonylferrate: Methyl 7-Oxoheptanoate and Methyl 7-Oxoöctanoate. Organic Syntheses. 1979. 59. 102.
- Book: Scholsser, M. . 2013 . Organometallics in Synthesis, Third Manual . Chicester, England . Wiley .
- Encyclopedia: Pike, R. D. . Disodium Tetracarbonylferrate(-II) . Encyclopedia of Reagents for Organic Synthesis . 2001 . 10.1002/047084289X.rd465 .
