Iron pentacarbonyl
Encyclopedia
Iron pentacarbonyl, also known as iron carbonyl, is the compound
with formula
5. Under standard conditions Fe(CO)5 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
. Fe(CO)5 is prepared by the reaction of fine iron
particles with carbon monoxide
. Fe(CO)5 is inexpensively purchased.
metal carbonyl
s; i.e. CO
is the only ligand complexed
with iron. Other examples include octahedral Cr(CO)6 and tetrahedral Ni(CO)4
. Most metal carbonyls have 18 valence electrons
, and Fe(CO)5 fits this pattern with 8 valence electrons on Fe and five pairs of electrons provided by the CO ligands. Reflecting its symmetrical structure and charge neutrality, Fe(CO)5 is volatile; it is one of the most frequently encountered liquid metal complexes. Fe(CO)5 adopts a trigonal bipyramidal structure with the Fe atom surrounded by five CO ligand
s: three in equatorial
positions and two axially bound. The Fe-C-O linkages are each linear.
Fe(CO)5 is the archetypal fluxional molecule due to the rapid interchange of the axial and equatorial CO groups via the Berry mechanism
on the NMR timescale
. Consequently, the13C NMR
spectrum exhibits only one signal due to the rapid interchange between nonequivalent CO sites.
Iron carbonyl is sometimes confused with carbonyl iron
, a high-purity metal prepared by decomposition of iron pentacarbonyl.
and Langer in 1891 as "a somewhat viscous liquid of a pale-yellow colour." Samples were prepared by treatment of finely divided, oxide-free iron powder with carbon monoxide at room temperature.
Photodissociation
of Fe(CO)5 produces Fe2(CO)9
, a yellow-orange solid, also described by Mond. When heated, Fe(CO)5 converts to small amounts of the metal cluster Fe3(CO)12
, a green solid. Simple thermolysis, however, is not a useful synthesis (see below).
Each iron carbonyl exhibits distinct reactivity.
in that the metal is treated with carbon monoxide to give a volatile gas. In the case of pentacarbonyliron, the reaction is more sluggish. It is necessary to use iron sponge as the starting material, and harsher reaction conditions of 5-30 MPa of carbon monoxide and 150-200 °C. Similar to the Mond process, sulfur acts as a catalyst. The crude pentacarbonyliron is purified by distillation. Ullmann's Encyclopedia of Industrial Chemistry
reports that there are only three plants manufacturing pentacarbonyliron; BASF in Germany and GAF in Alabama have capacities of 9000 and 1500-2000 tonnes/year respectively.
Most pentacarbonyliron produced is decomposed on site to give pure carbonyl iron
in analogy to carbonyl nickel. Some pentacarbonyliron is burned to give pure iron oxide
. Other uses of pentacarbonyliron are small in comparison.
s, tertiary phosphine
s and arsine
s, and alkene
s. Usually these ligands displace only one or two CO ligands, but certain acceptor ligands such as PF3 and isocyanides can proceed to tetra- and pentasubstitution. These reactions are often induced with a catalyst or light. Illustrative is the synthesis of the bis(triphenylphosphine) complex Fe(CO)3(P(C6H5)3)2. This transformation can be accomplished photochemically, but it is also induced by the addition of NaOH or NaBH4
. The catalyst attacks a CO ligand, which labilizes another CO ligand toward substitution. The electrophilicity of Fe(CO)4L is less than that of Fe(CO)5, so the nucleophilic catalyst, disengages and attacks another molecule of Fe(CO)5.
s gives the ferrous halides Fe(CO)4X2 for X = I, Br, Cl. These species, upon heating lose CO to give the ferrous halides, such as iron(II) chloride
.
Reduction of Fe(CO)5 with Na gives Na2Fe(CO)4
, "tetracarbonylferrate" also called Collman's reagent. The dianion is isoelectronic with Ni(CO)4 but highly nucleophilic
.
, but it is attacked by hydroxide
. Treatment of Fe(CO)5 with aqueous base produces [HFe(CO)4]-, the oxidation
of which gives Fe3(CO)12. Acidification of solutions of [HFe(CO)4]- gives H2Fe(CO)4, the first metal hydride ever reported.
and 1,3-butadiene
. One of the more historically significant derivatives is cyclobutadieneiron tricarbonyl
(C4H4)Fe(CO)3, where C4H4 is the otherwise unstable cyclobutadiene
. Receiving the greatest attention are complexes of the cyclohexadienes, the parent organic 1,4-dienes being available through the Birch reduction
s. 1,4-Dienes isomerize to the 1,3-dienes upon complexation.
Fe(CO)5 reacts in dicyclopentadiene
to form [Fe(C5H5)(CO)2]2, cyclopentadienyliron dicarbonyl dimer
. This compound, called "Fp dimer" can be considered a hybrid of ferrocene
and Fe(CO)5, although in terms of its reactivity, it resembles neither.
, iron pentacarbonyl was once used as an anti-knock agent in petrol in place of tetraethyllead. Two more modern alternative fuel additives are ferrocene
and methylcyclopentadienyl manganese tricarbonyl
. Fe(CO)5 is used in the production of "carbonyl iron
", a finely divided form of Fe, a material used in magnetic core
s of high-frequency coil
s for radio
s and television
s and for manufacture of the active ingredients of some radar absorbent material
s (e.g. iron ball paint). It is famous as a chemical precursor for the synthesis of various iron-based nanoparticle
s.
Iron pentacarbonyl has been found to be a strong flame speed inhibitor in oxygen based flames. A few hundred ppm of iron pentacarbonyl are known to reduce the flame speed of stoichiometric methane
-air flame by almost 50%. However due to its toxic nature it has not been used widely as a flame retardant.
. Like other metal carbonyls, Fe(CO)5 is flammable. It is, however, considerably less toxic than nickel tetracarbonyl.
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 formula
Chemical formula
A chemical formula or molecular formula is a way of expressing information about the atoms that constitute a particular chemical compound....
5. Under standard conditions Fe(CO)5 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
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...
. Fe(CO)5 is prepared by the reaction of fine iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...
particles with carbon monoxide
Carbon monoxide
Carbon 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...
. Fe(CO)5 is inexpensively purchased.
Properties
Iron pentacarbonyl is one of the homolepticHomoleptic
In inorganic chemistry, a homoleptic chemical compound is a metal compound with all ligands identical. The term uses a homo prefix to indicate that something is the same for all....
metal carbonyl
Metal carbonyl
Metal carbonyls are coordination complexes of transition metals with carbon monoxide ligands. These complexes may be homoleptic, that is containing only CO ligands, such as nickel carbonyl , but more commonly metal carbonyls contain a mix of ligands, such as Re3Cl...
s; i.e. CO
Carbon monoxide
Carbon 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...
is the only ligand complexed
Complex (chemistry)
In chemistry, a coordination complex or metal complex, is an atom or ion , bonded to a surrounding array of molecules or anions, that are in turn known as ligands or complexing agents...
with iron. Other examples include octahedral Cr(CO)6 and tetrahedral Ni(CO)4
Nickel carbonyl
Nickel carbonyl is the organonickel compound with the formula Ni4. This pale-yellow liquid is the principal carbonyl of nickel. It is an intermediate in the Mond process for the purification of nickel and a reagent in organometallic chemistry...
. Most metal carbonyls have 18 valence electrons
Electron counting
Electron counting is a formalism used for classifying compounds and for explaining or predicting electronic structure and bonding. Many rules in chemistry rely on electron-counting:...
, and Fe(CO)5 fits this pattern with 8 valence electrons on Fe and five pairs of electrons provided by the CO ligands. Reflecting its symmetrical structure and charge neutrality, Fe(CO)5 is volatile; it is one of the most frequently encountered liquid metal complexes. Fe(CO)5 adopts a trigonal bipyramidal structure with the Fe atom surrounded by five CO ligand
Ligand
In coordination chemistry, a ligand is an ion or molecule that binds to a central metal atom to form a coordination complex. The bonding between metal and ligand generally involves formal donation of one or more of the ligand's electron pairs. The nature of metal-ligand bonding can range from...
s: three in equatorial
Equatorial
Equatorial may refer to:* Equator of the Earth* Equatorial climate in meteorology* The ring-shaped outer boundary of the cross-section of a round three dimensional shape or object in geometry* The equatorial bond of a molecule in chemistry...
positions and two axially bound. The Fe-C-O linkages are each linear.
Fe(CO)5 is the archetypal fluxional molecule due to the rapid interchange of the axial and equatorial CO groups via the Berry mechanism
Berry mechanism
The Berry mechanism, or Berry pseudorotation mechanism, is a type of vibration causing molecules of certain geometries to isomerize by exchanging the two axial ligands for two of the equatorial ones. It is the most widely accepted mechanism for pseudorotation...
on the NMR timescale
NMR spectroscopy
Nuclear magnetic resonance spectroscopy, most commonly known as NMR spectroscopy, is a research technique that exploits the magnetic properties of certain atomic nuclei to determine physical and chemical properties of atoms or the molecules in which they are contained...
. Consequently, the13C NMR
NMR
NMR may refer to:Applications of Nuclear Magnetic Resonance:* Nuclear magnetic resonance* NMR spectroscopy* Solid-state nuclear magnetic resonance* Protein nuclear magnetic resonance spectroscopy* Proton NMR* Carbon-13 NMR...
spectrum exhibits only one signal due to the rapid interchange between nonequivalent CO sites.
Iron carbonyl is sometimes confused with carbonyl iron
Carbonyl iron
Carbonyl iron is a highly pure iron, prepared by chemical decomposition of purified iron pentacarbonyl. It usually has the appearance of grey powder, composed of spherical microparticles. Most of the impurities are carbon, oxygen, and nitrogen.BASF invented carbonyl iron powder in 1925, and claims...
, a high-purity metal prepared by decomposition of iron pentacarbonyl.
Synthesis and other iron carbonyls
The compound was described in a journal by MondLudwig Mond
Dr Ludwig Mond , was a German-born chemist and industrialist who took British nationality.-Education and career:...
and Langer in 1891 as "a somewhat viscous liquid of a pale-yellow colour." Samples were prepared by treatment of finely divided, oxide-free iron powder with carbon monoxide at room temperature.
Photodissociation
Photodissociation
Photodissociation, photolysis, or photodecomposition is a chemical reaction in which a chemical compound is broken down by photons. It is defined as the interaction of one or more photons with one target molecule....
of Fe(CO)5 produces Fe2(CO)9
Diiron nonacarbonyl
Diiron nonacarbonyl is an inorganic compound with the formula Fe29. This metal carbonyl is an important reagent in organometallic chemistry and of occasional use in organic synthesis. It is a more reactive source of Fe than Fe5 and less dangerous to handle because it is nonvolatile...
, a yellow-orange solid, also described by Mond. When heated, Fe(CO)5 converts to small amounts of the metal cluster Fe3(CO)12
Triiron dodecacarbonyl
Triiron dodecarbonyl is the chemical compound with the formula Fe312. It was one of the first metal carbonyl clusters synthesized. It is a more reactive source of iron than is iron pentacarbonyl.-General properties:...
, a green solid. Simple thermolysis, however, is not a useful synthesis (see below).
Each iron carbonyl exhibits distinct reactivity.
Industrial production and use
The industrial production of this compound is somewhat similar to the Mond processMond process
The Mond process, sometimes known as the carbonyl process is a technique created by Ludwig Mond in 1890 to extract and purify nickel. The process was used commercially before the end of the 19th century...
in that the metal is treated with carbon monoxide to give a volatile gas. In the case of pentacarbonyliron, the reaction is more sluggish. It is necessary to use iron sponge as the starting material, and harsher reaction conditions of 5-30 MPa of carbon monoxide and 150-200 °C. Similar to the Mond process, sulfur acts as a catalyst. The crude pentacarbonyliron is purified by distillation. Ullmann's Encyclopedia of Industrial Chemistry
Ullmann's Encyclopedia of Industrial Chemistry
Ullmann's Encyclopedia of Industrial Chemistry is a reference work which discusses many topics related to industrial chemistry. This work was originally published in German by Fritz Ullmann in 1914. The fifth edition was the first version which was published in English. This encyclopedia is...
reports that there are only three plants manufacturing pentacarbonyliron; BASF in Germany and GAF in Alabama have capacities of 9000 and 1500-2000 tonnes/year respectively.
Most pentacarbonyliron produced is decomposed on site to give pure carbonyl iron
Carbonyl iron
Carbonyl iron is a highly pure iron, prepared by chemical decomposition of purified iron pentacarbonyl. It usually has the appearance of grey powder, composed of spherical microparticles. Most of the impurities are carbon, oxygen, and nitrogen.BASF invented carbonyl iron powder in 1925, and claims...
in analogy to carbonyl nickel. Some pentacarbonyliron is burned to give pure iron oxide
Iron oxide
Iron oxides are chemical compounds composed of iron and oxygen. All together, there are sixteen known iron oxides and oxyhydroxides.Iron oxides and oxide-hydroxides are widespread in nature, play an important role in many geological and biological processes, and are widely utilized by humans, e.g.,...
. Other uses of pentacarbonyliron are small in comparison.
CO substitution reactions
Thousands of compounds are derived from Fe(CO)5. Substitution of CO by Lewis bases, L, to give derivatives Fe(CO)5-xLx. Common Lewis bases include isocyanideIsocyanide
An isocyanide is an organic compound with the functional group -N≡C. It is the isomer of the related cyanide , hence the prefix iso....
s, tertiary phosphine
Phosphine
Phosphine is the compound with the chemical formula PH3. It is a colorless, flammable, toxic gas. Pure phosphine is odourless, but technical grade samples have a highly unpleasant odor like garlic or rotting fish, due to the presence of substituted phosphine and diphosphine...
s and arsine
Arsine
Arsine is the chemical compound with the formula AsH3. This flammable, pyrophoric, and highly toxic gas is one of the simplest compounds of arsenic...
s, and alkene
Alkene
In organic chemistry, an alkene, olefin, or olefine is an unsaturated chemical compound containing at least one carbon-to-carbon double bond...
s. Usually these ligands displace only one or two CO ligands, but certain acceptor ligands such as PF3 and isocyanides can proceed to tetra- and pentasubstitution. These reactions are often induced with a catalyst or light. Illustrative is the synthesis of the bis(triphenylphosphine) complex Fe(CO)3(P(C6H5)3)2. This transformation can be accomplished photochemically, but it is also induced by the addition of NaOH or NaBH4
Sodium borohydride
Sodium borohydride, also known as sodium tetrahydridoborate, is an inorganic compound with the formula NaBH4. This white solid, usually encountered as a powder, is a versatile reducing agent that finds wide application in chemistry, both in the laboratory and on a technical scale. Large amounts are...
. The catalyst attacks a CO ligand, which labilizes another CO ligand toward substitution. The electrophilicity of Fe(CO)4L is less than that of Fe(CO)5, so the nucleophilic catalyst, disengages and attacks another molecule of Fe(CO)5.
Oxidation and reduction
Most metal carbonyls can be halogenated. Thus, treatment of Fe(CO)5 with halogenHalogen
The halogens or halogen elements are a series of nonmetal elements from Group 17 IUPAC Style of the periodic table, comprising fluorine , chlorine , bromine , iodine , and astatine...
s gives the ferrous halides Fe(CO)4X2 for X = I, Br, Cl. These species, upon heating lose CO to give the ferrous halides, such as iron(II) chloride
Iron(II) chloride
Iron chloride, also known as ferrous chloride, is the chemical compound of formula FeCl2. It is a paramagnetic solid with a high melting point, and is usually obtained as an off-white solid. FeCl2 crystallizes from water as the greenish tetrahydrate, which is the form that is most commonly...
.
Reduction of Fe(CO)5 with Na gives Na2Fe(CO)4
Disodium tetracarbonylferrate
Disodium tetracarbonylferrate is the chemical compound with the formula Na2[Fe4]. This oxygen-sensitive colourless solid is employed in organic synthesis", mainly to synthesise aldehydes. It is commonly used with dioxane complexed to the sodium cation, this dioxane solvate being known as Collman's...
, "tetracarbonylferrate" also called Collman's reagent. The dianion is isoelectronic with Ni(CO)4 but highly nucleophilic
Nucleophile
A nucleophile is a species that donates an electron-pair to an electrophile to form a chemical bond in a reaction. All molecules or ions with a free pair of electrons can act as nucleophiles. Because nucleophiles donate electrons, they are by definition Lewis bases.Nucleophilic describes the...
.
Acid-base reactions
Fe(CO)5 is not readily protonatedProtonation
In chemistry, protonation is the addition of a proton to an atom, molecule, or ion. Some classic examples include*the protonation of water by sulfuric acid:*the protonation of isobutene in the formation of a carbocation:2C=CH2 + HBF4 → 3C+ + BF4−*the protonation of ammonia in the...
, but it is attacked by hydroxide
Hydroxide
Hydroxide is a diatomic anion with chemical formula OH−. It consists of an oxygen and a hydrogen atom held together by a covalent bond, and carrying a negative electric charge. It is an important but usually minor constituent of water. It functions as a base, as a ligand, a nucleophile, and a...
. Treatment of Fe(CO)5 with aqueous base produces [HFe(CO)4]-, the oxidation
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
of which gives Fe3(CO)12. Acidification of solutions of [HFe(CO)4]- gives H2Fe(CO)4, the first metal hydride ever reported.
Diene adducts
Dienes react with Fe(CO)5 to give (diene)Fe(CO)3, wherein two CO ligands have been replaced by two olefins. Many dienes undergo this reaction, notably norbornadieneNorbornadiene
Norbornadiene is an organic compound. This bicyclic hydrocarbon is the most stable diolefin derived from the norbornane and norbornene. Norbornadiene is primarily of interest as a ligand in homogeneous catalysis, but it has been heavily studied due to its high reactivity and distinctive...
and 1,3-butadiene
1,3-Butadiene
1,3-Butadiene is a simple conjugated diene with the formula C4H6. It is an important industrial chemical used as a monomer in the production of synthetic rubber. When the word butadiene is used, most of the time it refers to 1,3-butadiene....
. One of the more historically significant derivatives is cyclobutadieneiron tricarbonyl
Cyclobutadieneiron tricarbonyl
Cyclobutadieneiron tricarbonyl or Fe3 is an organometallic complex of cyclobutadiene and an iron metal carbonyl. The chemical compound is used in organic chemistry as a precursor for cyclobutadiene...
(C4H4)Fe(CO)3, where C4H4 is the otherwise unstable cyclobutadiene
Cyclobutadiene
Cyclobutadiene is the smallest [n]-annulene , an extremely unstable hydrocarbon having a lifetime shorter than five seconds in the free state. It has chemical formula 44 and a rectangular structure verified by infrared studies. This is in contrast to the square geometry predicted by simple Hückel...
. Receiving the greatest attention are complexes of the cyclohexadienes, the parent organic 1,4-dienes being available through the Birch reduction
Birch reduction
The Birch Reduction is an organic reaction which is particularly useful in synthetic organic chemistry. The reaction was reported in 1944 by the Australian chemist Arthur Birch working in the Dyson Perrins Laboratory in the University of Oxford, building on earlier work by Wooster and Godfrey in...
s. 1,4-Dienes isomerize to the 1,3-dienes upon complexation.
Fe(CO)5 reacts in dicyclopentadiene
Dicyclopentadiene
Dicyclopentadiene, abbreviated DCPD, is a chemical compound with formula C10H12. At room temperature, it is a white crystalline solid with a camphor-like odor. Its energy density is 10,975 Wh/l....
to form [Fe(C5H5)(CO)2]2, cyclopentadienyliron dicarbonyl dimer
Cyclopentadienyliron dicarbonyl dimer
Cyclopentadienyliron dicarbonyl dimer is an organometallic compound with the formula 2Fe24, also abbreviated Cp2Fe24. It is called Fp2 or "fip dimer." It is a dark reddish-purple crystalline solid, which is readily soluble in moderately polar organic solvents such as chloroform and pyridine, but...
. This compound, called "Fp dimer" can be considered a hybrid of ferrocene
Ferrocene
Ferrocene is an organometallic compound with the formula Fe2. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are also known as sandwich compounds...
and Fe(CO)5, although in terms of its reactivity, it resembles neither.
Other uses
In EuropeEurope
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, iron pentacarbonyl was once used as an anti-knock agent in petrol in place of tetraethyllead. Two more modern alternative fuel additives are ferrocene
Ferrocene
Ferrocene is an organometallic compound with the formula Fe2. It is the prototypical metallocene, a type of organometallic chemical compound consisting of two cyclopentadienyl rings bound on opposite sides of a central metal atom. Such organometallic compounds are also known as sandwich compounds...
and methylcyclopentadienyl manganese tricarbonyl
Methylcyclopentadienyl manganese tricarbonyl
Methylcyclopentadienyl manganese tricarbonyl is an organomanganese compound with the formula Mn3. Marketed initially in 1958 as a supplement to the gasoline additive tetraethyl lead to increase the fuel's octane rating, MMT was later used in unleaded gasoline...
. Fe(CO)5 is used in the production of "carbonyl iron
Carbonyl iron
Carbonyl iron is a highly pure iron, prepared by chemical decomposition of purified iron pentacarbonyl. It usually has the appearance of grey powder, composed of spherical microparticles. Most of the impurities are carbon, oxygen, and nitrogen.BASF invented carbonyl iron powder in 1925, and claims...
", a finely divided form of Fe, a material used in magnetic core
Magnetic core
A magnetic core is a piece of magnetic material with a high permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, inductors and magnetic assemblies. It is made of ferromagnetic metal such...
s of high-frequency coil
Coil
A coil is a series of loops. A coiled coil is a structure in which the coil itself is in turn also looping.-Electromagnetic coils:An electromagnetic coil is formed when a conductor is wound around a core or form to create an inductor or electromagnet...
s for radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
s and television
Television
Television is a telecommunication medium for transmitting and receiving moving images that can be monochrome or colored, with accompanying sound...
s and for manufacture of the active ingredients of some radar absorbent material
Radar absorbent material
Radar-absorbent material, or RAM, is a class of materials used in stealth technology to disguise a vehicle or structure from radar detection. A material's absorbency at a given frequency of radar wave depends upon its composition...
s (e.g. iron ball paint). It is famous as a chemical precursor for the synthesis of various iron-based nanoparticle
Nanoparticle
In nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...
s.
Iron pentacarbonyl has been found to be a strong flame speed inhibitor in oxygen based flames. A few hundred ppm of iron pentacarbonyl are known to reduce the flame speed of stoichiometric methane
Methane
Methane is a chemical compound with the chemical formula . It is the simplest alkane, the principal component of natural gas, and probably the most abundant organic compound on earth. The relative abundance of methane makes it an attractive fuel...
-air flame by almost 50%. However due to its toxic nature it has not been used widely as a flame retardant.
Toxicity and hazards
Fe(CO)5 is toxic, which is of concern because of its volatility (vapour pressure: 21 mmHg at 20 °C). If inhaled, iron pentacarbonyl may cause lung irritation, toxic pneumonitis, or pulmonary edemaPulmonary edema
Pulmonary edema , or oedema , is fluid accumulation in the air spaces and parenchyma of the lungs. It leads to impaired gas exchange and may cause respiratory failure...
. Like other metal carbonyls, Fe(CO)5 is flammable. It is, however, considerably less toxic than nickel tetracarbonyl.