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A metal carbido complex is a
Most molecular carbido complexes are clusters, usually featuring carbide as a six-fold
The "naked" carbido ligand is weakly basic, forming complexes with other metal centers. The C-M bond is typically found to be around 1.65 angstroms. The 13
coordination complex
A coordination complex consists of a central atom or ion, which is usually metallic and is called the ''coordination centre'', and a surrounding array of bound molecules or ions, that are in turn known as ''ligands'' or complexing agents. Many ...
that contains a carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent
In chemistry, the valence (US spelling) or valency (British spelling) of an element is the measure of its combining capacity with o ...
atom as a ligand
In coordination chemistry, a ligand is an ion or molecule (functional group) that binds to a central metal atom to form a coordination complex. The bonding with the metal generally involves formal donation of one or more of the ligand's electr ...
. Carbido complexes are a molecular subclass of carbide
In chemistry, a carbide usually describes a compound composed of carbon and a metal. In metallurgy, carbiding or carburizing is the process for producing carbide coatings on a metal piece.
Interstitial / Metallic carbides
The carbides of the ...
s, which are prevalent. Carbido complexes represent models for intermediates in Fischer–Tropsch synthesis and related catalytic processes. They are also used as precursors for the synthesis of more complicated carbides. They are analogous to metal nitrido complexes.
Carbido clusters
Most molecular carbido complexes are clusters, usually featuring carbide as a six-fold bridging ligand
In coordination chemistry, a bridging ligand is a ligand that connects two or more atoms, usually metal ions. The ligand may be atomic or polyatomic. Virtually all complex organic compounds can serve as bridging ligands, so the term is usually r ...
. Examples include , and . The iron
Iron () is a chemical element with symbol Fe (from la, ferrum) and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, right in f ...
carbonyl carbides exist not only in the encapsulated carbon () but also with exposed carbon centres as in and .
Clusters without CO ligands are also known.
Doubly bridging carbide ligands
Bridging carbido ligands can be subdivided into three classes: *cumulenic , *metallocarbyne , and *polar covalent . Cumulenic compounds generally bridge two metal atoms of the same element and are symmetrical. However, there are exceptions to this.Terminal carbido ligands
In rare cases, carbido ligands are terminal. One example is with a Ru-C distance of 163 pm, typical for a triple bond. The complex can be obtained by metathesis of vinyl acetate to give results in a metastable complex, which eliminates acetic acid.
The "naked" carbido ligand is weakly basic, forming complexes with other metal centers. The C-M bond is typically found to be around 1.65 angstroms. The 13CNMR Carbon-13 (C13) nuclear magnetic resonance (most commonly known as carbon-13 NMR spectroscopy or 13C NMR spectroscopy or sometimes simply referred to as carbon NMR) is the application of nuclear magnetic resonance (NMR) spectroscopy to carbon. It i ...
resonance values for the carbido carbons vary widely, but range from δ211-406. Another example of a terminal carbido complex is (Mo-C distance of 172 pm), which forms upon deprotonation of the methylidyne precursor.
See also
* Metallocarbohedryne ("met-car"), a stable cluster with formula (M = Ti, Zr, V, etc.)References
{{Coordination complexes Organometallic compounds Organometallic chemistry