Chemistry:Actinocene

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Short description: Class of chemical compounds
Skeletal formula of uranocene
Skeletal formula
Uranocene ball-and-stick model
Ball-and-stick
Uranocene space-filling model
Space-filling
Uranocene molecular representations showing the U atom sandwiched between 2 COT2- ligands

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 C8H2−8) bound to an actinide-metal center (An) in the oxidation state IV, resulting in the general formula An(C8H8)2.[1][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.[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]

Bonding

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]

See also

References

  1. ↑ Minasian, Stefan G.; Keith, Jason M. (2014). "New evidence for 5f covalency in actinocenes determined from carbon K-edge XAS and electronic structure theory". Chem. Sci. 5 (1): 351–359. doi:10.1039/C3SC52030G. https://zenodo.org/record/1230028. 
  2. ↑ 2.0 2.1 Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements. Butterworth-Heinemann. pp. 1278–1280. ISBN 978-0-08-037941-8. 
  3. ↑ 3.0 3.1 Seyferth, D. (2004). "Uranocene. The First Member of a New Class of Organometallic Derivatives of the f Elements". Organometallics 23 (15): 3562–3583. doi:10.1021/om0400705. 
  4. ↑ Goffart, J.; Fuger, J.; Brown, D.; Duyckaerts, G. (1974-05-01). "On the cyclooctatetraenyl compounds of actinide elements part II. Bis-(cyclooctatetraenyl) protactinium(IV)" (in en). Inorganic and Nuclear Chemistry Letters 10 (5): 413–419. doi:10.1016/0020-1650(74)80119-4. ISSN 0020-1650. https://dx.doi.org/10.1016%2F0020-1650%2874%2980119-4. 
  5. ↑ Avdeef, Alex; Raymond, Kenneth N.; Hodgson, Keith O.; Zalkin, Allan (1972-05-01). "Two isostructural actinide .pi. complexes. Crystal and molecular structure of bis(cyclooctatetraenyl)uranium(IV), U(C8H8)2, and bis(cyclooctatetraenyl)thorium(IV), Th(C8H8)2". Inorganic Chemistry 11 (5): 1083–1088. doi:10.1021/ic50111a034. ISSN 0020-1669. https://doi.org/10.1021/ic50111a034. 
  6. ↑ De Ridder, D. J. A.; Rebizant, J.; Apostolidis, C.; Kanellakopulos, B.; Dornberger, E. (1996-03-15). "Bis(cyclooctatetraenyl)neptunium(IV)" (in en). Acta Crystallographica Section C: Crystal Structure Communications 52 (3): 597–600. doi:10.1107/S0108270195013047. ISSN 0108-2701. http://scripts.iucr.org/cgi-bin/paper?S0108270195013047. 
  7. ↑ 7.0 7.1 Windorff, Cory J.; Sperling, Joseph M.; Albrecht-Schönzart, Thomas E.; Bai, Zhuanling; Evans, William J.; Gaiser, Alyssa N.; Gaunt, Andrew J.; Goodwin, Conrad A. P. et al. (2020-09-21). "A Single Small-Scale Plutonium Redox Reaction System Yields Three Crystallographically-Characterizable Organoplutonium Complexes" (in en). Inorganic Chemistry 59 (18): 13301–13314. doi:10.1021/acs.inorgchem.0c01671. ISSN 0020-1669. PMID 32910649. https://pubs.acs.org/doi/10.1021/acs.inorgchem.0c01671. 
  8. ↑ 8.0 8.1 8.2 Apostolidis, Christos; Walter, Olaf; Vogt, Jochen; Liebing, Phil; Maron, Laurent; Edelmann, Frank T. (2017-04-24). "A Structurally Characterized Organometallic Plutonium(IV) Complex" (in en). Angewandte Chemie International Edition 56 (18): 5066–5070. doi:10.1002/anie.201701858. PMID 28371148. 
  9. ↑ 9.0 9.1 Kerridge, Andrew (2014). "f-Orbital covalency in the actinocenes (An = Th–Cm): multiconfigurational studies and topological analysis". RSC Advances 4 (24): 12078–12086. doi:10.1039/C3RA47088A. Bibcode: 2014RSCAd...412078K. http://discovery.ucl.ac.uk/1426903/1/c3ra47088a.pdf. 



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