Английская Википедия:Actinocene

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Actinocenes are a family of organoactinide compounds consisting of metallocenes containing elements from the actinide series. They typically have a sandwich structure with two dianionic cyclooctatetraenyl ligands (COT^2-, which is Шаблон:Chem) bound to an actinide-metal center (An) in the oxidation state IV, resulting in the general formula An(C₈H₈)₂.

Characterised actinocenes

Name	Formula	AnIV centre	First synthesis	Crystal colour	An–COT distance (Å)	Space group
Thorocene	Th(C8H8)2	Th	1969	bright yellow	2.004	P21/n
Protactinocene	Pa(C8H8)2	Pa	1974	yellowish	–	P21/n
Uranocene	U(C8H8)2	U	1968	deep green	1.926	P21/n
Neptunocene	Np(C8H8)2	Np	1970	yellow-brown	1.909	P21/n
Plutonocene	Pu(C8H8)2	Pu	1970	dark red	1.898	I2/m

The most studied actinocene is uranocene, U(C₈H₈)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(C₈H₈)₂), thorocene (Th(C₈H₈)₂), neptunocene (Np(C₈H₈)₂), and plutonocene (Pu(C₈H₈)₂). Especially the latter two, neptunocene and plutonocene, have not been extensively studied experimentally since the 1980s because of the radiation hazard they pose.

Bonding

The actinide-cyclooctatetraenyl bonding has been of interest for multiple theoretical studies. Computational chemistry methods indicate bonding with a large covalent character resulting mainly from the mixing of actinide 6d orbitals with ligand π-orbitals, with a smaller interaction involving the actinide 5f and ligand π-orbitals. The covalent component is characterised by donation of electron density to the actinide.

Analogous sandwiched M(C₈H₈)₂ compounds also exist for lanthanides M = Nd, Tb, and Yb, but therein the bonding is mostly ionic rather than covalent (see lanthanocenes).

See also

• Organoactinide chemistry
• f-block metallocene