Iron pentacarbonyl, also known as iron carbonyl, is the compound with formula Fe(CO)5. Under standard conditions Fe(CO)5 is a free-flowing, straw-colored liquid with a pungent odour. Older samples appear darker. This compound is a common precursor to diverse iron compounds, including many that are useful in small scale organic synthesis.
In coordination chemistry, hapticity is the coordination of a ligand to a metal center via an uninterrupted and contiguous series of atoms. The hapticity of a ligand is described with the Greek letter η ('eta'). For example, η2 describes a ligand that coordinates through 2 contiguous atoms. In general the η-notation only applies when multiple atoms are coordinated. In addition, if the ligand coordinates through multiple atoms that are not contiguous then this is considered denticity, and the κ-notation is used once again. When naming complexes care should be taken not to confuse η with μ ('mu'), which relates to bridging ligands.
Cyclobutadieneiron tricarbonyl is an organoiron compound with the formula Fe(C4H4)(CO)3. It is a yellow solid that is soluble in organic solvents. It has been used in organic chemistry as a precursor for cyclobutadiene, which is an elusive species in the free state.
Iron shows the characteristic chemical properties of the transition metals, namely the ability to form variable oxidation states differing by steps of one and a very large coordination and organometallic chemistry: indeed, it was the discovery of an iron compound, ferrocene, that revolutionalized the latter field in the 1950s. Iron is sometimes considered as a prototype for the entire block of transition metals, due to its abundance and the immense role it has played in the technological progress of humanity. Its 26 electrons are arranged in the configuration [Ar]3d64s2, of which the 3d and 4s electrons are relatively close in energy, and thus it can lose a variable number of electrons and there is no clear point where further ionization becomes unprofitable.
Diiron nonacarbonyl is an organometallic compound with the formula Fe2(CO)9. 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(0) than Fe(CO)5. This micaceous orange solid is virtually insoluble in all common solvents.
Benzylideneacetone is the organic compound described by the formula C6H5CH=CHC(O)CH3. Although both cis- and trans-isomers are possible for the α,β-unsaturated ketone, only the trans isomer is observed. Its original preparation demonstrated the scope of condensation reactions to construct new, complex organic compounds. Benzylideneacetone is used as a flavouring ingredient in food and perfumes.
Disodium tetracarbonylferrate is the organoiron compound with the formula Na2[Fe(CO)4]. It is always used as a solvate, e.g., with tetrahydrofuran or dimethoxyethane, which bind to the sodium cation. 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.
Triethyl phosphite is an organophosphorus compound, specifically a phosphite ester, with the formula P(OCH2CH3)3, often abbreviated P(OEt)3. It is a colorless, malodorous liquid. It is used as a ligand in organometallic chemistry and as a reagent in organic synthesis.
In organometallic chemistry, a transition metal indenyl complex is a coordination compound that contains one or more indenyl ligands. The indenyl ligand is formally the anion derived from deprotonation of indene. The η5-indenyl ligand is related to the η5cyclopentadienyl anion (Cp), thus indenyl analogues of many cyclopentadienyl complexes are known. Indenyl ligands lack the 5-fold symmetry of Cp, so they exhibit more complicated geometries. Furthermore, some indenyl complexes also exist with only η3-bonding mode. The η5- and η3-bonding modes sometimes interconvert.
Organomanganese chemistry is the chemistry of organometallic compounds containing a carbon to manganese chemical bond. In a 2009 review, Cahiez et al. argued that as manganese is cheap and benign, organomanganese compounds have potential as chemical reagents, although currently they are not widely used as such despite extensive research.
Organoiron chemistry is the chemistry of iron compounds containing a carbon-to-iron chemical bond. Organoiron compounds are relevant in organic synthesis as reagents such as iron pentacarbonyl, diiron nonacarbonyl and disodium tetracarbonylferrate. While iron adopts oxidation states from Fe(−II) through to Fe(VII), Fe(IV) is the highest established oxidation state for organoiron species. Although iron is generally less active in many catalytic applications, it is less expensive and "greener" than other metals. Organoiron compounds feature a wide range of ligands that support the Fe-C bond; as with other organometals, these supporting ligands prominently include phosphines, carbon monoxide, and cyclopentadienyl, but hard ligands such as amines are employed as well.
(Mesitylene)molybdenum tricarbonyl is an organomolybdenum compound derived from the aromatic compound mesitylene (1,3,5-trimethylbenzene) and molybdenum carbonyl. It exists as pale yellow crystals, which are soluble in organic solvents but decompose when in solution. It has been examined as a catalyst and reagent.
Cyclopentadienyliron dicarbonyl dimer is an organometallic compound with the formula [(η5-C5H5)Fe(CO)2]2, often abbreviated to Cp2Fe2(CO)4, [CpFe(CO)2]2 or even Fp2, with the colloquial name "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 less soluble in carbon tetrachloride and carbon disulfide. Cp2Fe2(CO)4 is insoluble in but stable toward water. Cp2Fe2(CO)4 is reasonably stable to storage under air and serves as a convenient starting material for accessing other Fp (CpFe(CO)2) derivatives (described below).
The Knölker complex is an organoiron compound, which is a catalyst for transfer hydrogenation. The complex features an hydroxycyclopentadienyl ligand bound to an Fe(CO)2H centre. It is generated by the corresponding cyclopentadienone tricarbonyl by treatment with base followed by acidification. The compound is related to the organoruthenium compound called Shvo's complex, a hydroxycyclopentadienyl derivative that also functions as a catalyst for hydrogenation.
Half sandwich compounds, also known as piano stool complexes, are organometallic complexes that feature a cyclic polyhapto ligand bound to an MLn center, where L is a unidentate ligand. Thousands of such complexes are known. Well-known examples include cyclobutadieneiron tricarbonyl and (C5H5)TiCl3. Commercially useful examples include (C5H5)Co(CO)2, which is used in the synthesis of substituted pyridines, and methylcyclopentadienyl manganese tricarbonyl, an antiknock agent in petrol.
Tetramesityldiiron is an organoiron compound with the formula Fe2(C6H2(CH3)3)4. It is a red, air-sensitive solid that is used as a precursor to other iron complexes. It adopts a centrosymmetric structure. The complex is a Lewis acid, forming monomeric adducts, e.g. Fe(C6H2(CH3)3)2pyridine2. The complex is prepared by treating ferrous halides with the Grignard reagent formed from mesityl bromide:
In organometallic chemistry, a transition metal alkene complex is a coordination compound containing one or more alkene ligands. The inventory is large. Such compounds are intermediates in many catalytic reactions that convert alkenes to other organic products.
In organoiron chemistry, a ferrole is a type of diiron complex containing the (OC)3FeC4R4 heterocycle that is pi-bonded to a Fe(CO)3 group. These compounds have Fe-Fe bonds (ca. 252 pm) and semi-bridging CO ligands (Fe-C distances = 178, 251 pm). They are typically air-stable, soluble in nonpolar solvents, and red-orange in color.
In 1956, Longuet-Higgins and Orgel predicted the existence of transition-metal cyclobutadiene complexes, in which the degenerate eg orbital of cyclobutadiene has the correct symmetry for π interaction with the dxz and dyz orbitals of the proper metal. The compound was synthesized three years after the prediction and it serves as a beautiful case of theory before experiment. This successful attempt opens the door for the formation of novel compounds containing other organic ligands which in their free state are highly reactive molecules. Of all those reactive molecules, trimethylenemethane (TMM) has the most natural derivation from the cyclobutadiene complexes and in 1966, Emerson and co-workers reported the first trimethylenemethane (TMM) transition metal complex, (CO)3FeC(CH2)3, which became the starting point of the legends of trimethylenemethane complexes. Some good reviews on this aspect could be served as further resources for this topic.
In organometallic chemistry, (diene)iron tricarbonyl describes a diverse family of related coordination complexes consisting of a diene ligand coordinated to a Fe(CO)3 center. Often the diene is conjugated, e.g., butadiene, but the family includes nonconjugated dienes as well. The compounds are yellow, air-stable, often low-melting, and soluble in hydrocarbon solvents. The motif is so robust that even unstable dienes form easily characterized derivatives, such as norbornadienone and cyclobutadiene.
