Disodium tetracarbonylferrate
Encyclopedia
Disodium tetracarbonylferrate is the chemical compound
with the formula Na2[Fe(CO)4]. This oxygen
-sensitive colourless solid is employed in organic synthesis
", mainly to synthesise aldehyde
s. It is commonly used with dioxane complexed to the sodium cation, this dioxane solvate being known as Collman's
reagent. The tetracarbonylferrate dianion is tetrahedral.
was reported by Cooke in 1970. 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.
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.
Disodium tetracarbonylferrate reacts with alkyl halides (RX) to produce alkyl complexes:
Such iron alkyls can be converted to the corresponding carboxylic acid
and acid halides:
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.
Chemical compound
A chemical compound is a pure chemical substance consisting of two or more different chemical elements that can be separated into simpler substances by chemical reactions. Chemical compounds have a unique and defined chemical structure; they consist of a fixed ratio of atoms that are held together...
with the formula Na2[Fe(CO)4]. This oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
-sensitive colourless solid is employed in organic synthesis
Organic synthesis
Organic synthesis is a special branch of chemical synthesis and is concerned with the construction of organic compounds via organic reactions. Organic molecules can often contain a higher level of complexity compared to purely inorganic compounds, so the synthesis of organic compounds has...
", mainly to synthesise aldehyde
Aldehyde
An aldehyde is an organic compound containing a formyl group. This functional group, with the structure R-CHO, consists of a carbonyl center bonded to hydrogen and an R group....
s. It is commonly used with dioxane complexed to the sodium cation, this dioxane solvate being known as Collman's
James P. Collman
James P. Collman is an American Professor of Chemistry. He is currently serving at Stanford University in California.Collman is considered a pioneer in bioinorganic and biomimetic chemistry...
reagent. The tetracarbonylferrate dianion is tetrahedral.
Synthesis
The reagentReagent
A reagent is a "substance or compound that is added to a system in order to bring about a chemical reaction, or added to see if a reaction occurs." Although the terms reactant and reagent are often used interchangeably, a reactant is less specifically a "substance that is consumed in the course of...
was reported by Cooke in 1970. The current synthesis entails the reduction of a solution of iron pentacarbonyl
Iron pentacarbonyl
Iron pentacarbonyl, also known as iron carbonyl, is the compound with formula 5. Under standard conditions Fe5 is a free-flowing, straw-colored liquid with a pungent odour. This compound is a common precursor to diverse iron compounds, including many that are useful in organic synthesis. Fe5 is...
in tetrahydrofuran
Tetrahydrofuran
Tetrahydrofuran is a colorless, water-miscible organic liquid with low viscosity at standard temperature and pressure. This heterocyclic compound has the chemical formula 4O. As one of the most polar ethers with a wide liquid range, it is a useful solvent. Its main use, however, is as a precursor...
by sodium naphthenide. The efficiency of the synthesis depends on the quality of the iron pentacarbonyl.
- Fe(CO)5 + 2 NaSodiumSodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
→ Na2[Fe(CO)4] + COCarbon monoxideCarbon monoxide , also called carbonous oxide, is a colorless, odorless, and tasteless gas that is slightly lighter than air. It is highly toxic to humans and animals in higher quantities, although it is also produced in normal animal metabolism in low quantities, and is thought to have some normal...
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:- Na2[Fe(CO)4] + RBr → Na[RFe(CO)4] + NaBrSodium bromideSodium bromide is an inorganic compound with the formula NaBr. It is a high-melting white, crystalline solid that resembles sodium chloride. It is a widely used source of the bromide ion and has many applications.-Synthesis, structure, reactions:...
This solution is then treated sequentially with PPh3
Triphenylphosphine
Triphenylphosphine is a common organophosphorus compound with the formula P3 - often abbreviated to PPh3 or Ph3P. It is widely used in the synthesis of organic and organometallic compounds. PPh3 exists as relatively air stable, colorless crystals at room temperature...
and then acetic acid
Acetic acid
Acetic acid is an organic compound with the chemical formula CH3CO2H . It is a colourless liquid that when undiluted is also called glacial acetic acid. Acetic acid is the main component of vinegar , and has a distinctive sour taste and pungent smell...
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
Acyl
An acyl group is a functional group derived by the removal of one or more hydroxyl groups from an oxoacid, including inorganic acids.In organic chemistry, the acyl group is usually derived from a carboxylic acid . Therefore, it has the formula RCO-, where R represents an alkyl group that is...
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] + HClHydrogen chlorideThe compound hydrogen chloride has the formula HCl. At room temperature, it is a colorless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric humidity. Hydrogen chloride gas and hydrochloric acid are important in technology and industry...
→ 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
Carboxylic acid
Carboxylic acids are organic acids characterized by the presence of at least one carboxyl group. The general formula of a carboxylic acid is R-COOH, where R is some monovalent functional group...
and acid halides:
- Na[RFe(CO)4] + O2OxygenOxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...
, 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.