Actinocenes are a family of
organoactinide
Organoactinide chemistry is the science exploring the properties, structure and reactivity of organoactinide compounds, which are organometallic compounds containing a carbon to actinide chemical bond.
Like most organometallic compounds, the orga ...
compounds consisting of
metallocenes
A metallocene is a compound typically consisting of two cyclopentadienyl anions (, abbreviated Cp) bound to a metal center (M) in the oxidation state II, with the resulting general formula Closely related to the metallocenes are the metallocene de ...
containing
elements from the
actinide
The actinide () or actinoid () series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The inform ...
series. They typically have a
sandwich
A sandwich is a food typically consisting of vegetables, sliced cheese or meat, placed on or between slices of bread, or more generally any dish wherein bread serves as a container or wrapper for another food type. The sandwich began as a po ...
structure with two dianionic
cyclooctatetraenyl
1,3,5,7-Cyclooctatetraene (COT) is an unsaturated derivative of cyclooctane, with the formula C8H8. It is also known as nnulene. This polyunsaturated hydrocarbon is a colorless to light yellow flammable liquid at room temperature. Because of ...
ligands (COT
2-, which is ) bound to an actinide-metal center (An) in the
oxidation state
In chemistry, the oxidation state, or oxidation number, is the hypothetical charge of an atom if all of its bonds to different atoms were fully ionic. It describes the degree of oxidation (loss of electrons) of an atom in a chemical compound. C ...
IV, resulting in the general formula An(C
8H
8)
2.
Characterised actinocenes
The most studied actinocene is uranocene, U(C
8H
8)
2, which in 1968 was the first member of this family to be synthesised and is still viewed as the archetypal example.
Other actinocenes that have been synthesised are protactinocene (Pa(C
8H
8)
2), thorocene (Th(C
8H
8)
2), neptunocene
(Np(C
8H
8)
2), and plutonocene
(Pu(C
8H
8)
2). Especially the latter two, neptunocene and plutonocene, have not been extensively studied experimentally since the 1980s because of the
radiation
In physics, radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes:
* ''electromagnetic radiation'', such as radio waves, microwaves, infrared, visi ...
hazard they pose.
Bonding
The actinide-cyclooctatetraenyl
bonding has been of interest for multiple theoretical studies.
Computational chemistry
Computational chemistry is a branch of chemistry that uses computer simulation to assist in solving chemical problems. It uses methods of theoretical chemistry, incorporated into computer programs, to calculate the structures and properties of m ...
methods indicate bonding with a large
covalent
A covalent bond is a chemical bond that involves the sharing of electrons to form electron pairs between atoms. These electron pairs are known as shared pairs or bonding pairs. The stable balance of attractive and repulsive forces between atoms ...
character resulting mainly from the mixing of actinide 6''d'' orbitals with ligand π-
orbitals, with a smaller interaction involving the actinide 5''f'' and ligand π-orbitals.
The covalent component is characterised by
donation
A donation is a gift for charity, humanitarian aid, or to benefit a cause. A donation may take various forms, including money, alms, services, or goods such as clothing, toys, food, or vehicles. A donation may satisfy medical needs such as blo ...
of electron density to the actinide.
Analogous sandwiched M(C
8H
8)
2 compounds also exist for
lanthanides
The lanthanide () or lanthanoid () series of chemical elements comprises the 15 metallic chemical elements with atomic numbers 57–71, from lanthanum through lutetium. These elements, along with the chemically similar elements scandium and ytt ...
M =
Nd,
Tb, and
Yb, but therein the bonding is
mostly ionic rather than covalent (see
lanthanocenes).
See also
*
Organoactinide chemistry
Organoactinide chemistry is the science exploring the properties, structure and reactivity of organoactinide compounds, which are organometallic compounds containing a carbon to actinide chemical bond.
Like most organometallic compounds, the orga ...
*
f-block metallocene
References
{{thorium compounds
Organoactinide compounds
Metallocenes