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 (COT2-, which is C
8H2−
8) bound to an actinide-metal center (An) in the
oxidation state IV, resulting in the general formula An(C8H8)2.
[1]
[2]
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. [2] [3] Other actinocenes that have been synthesised are protactinocene [4] (Pa(C8H8)2), thorocene [5] (Th(C8H8)2), neptunocene [6] (Np(C8H8)2), and plutonocene [7] [8] (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. [7] [8]
The actinide-cyclooctatetraenyl bonding has been of interest for multiple theoretical studies. [8] [9] 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. [9] 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). [3]
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 (COT2-, which is C
8H2−
8) bound to an actinide-metal center (An) in the
oxidation state IV, resulting in the general formula An(C8H8)2.
[1]
[2]
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. [2] [3] Other actinocenes that have been synthesised are protactinocene [4] (Pa(C8H8)2), thorocene [5] (Th(C8H8)2), neptunocene [6] (Np(C8H8)2), and plutonocene [7] [8] (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. [7] [8]
The actinide-cyclooctatetraenyl bonding has been of interest for multiple theoretical studies. [8] [9] 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. [9] 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). [3]