Class of chemical compounds
Uranocene molecular representations showing the U atom sandwiched between 2 COT
2− ligands
Actinocenes are a family oforganoactinide compounds consisting ofmetallocenes containingelements from theactinide series. They typically have asandwich structure with two dianioniccyclooctatetraenyl ligands (COT2− , which isC8 2− 8 ) bound to an actinide-metal center (An) in theoxidation state IV, resulting in the general formula An(C8 H8 )2 .[ 1] [ 2]
Characterised actinocenes [ edit ] Name Formula AnIV centre First synthesis Crystal colour An–COT distance (Å) Space group Thorocene Th(C8 H8 )2 Th 1969 bright yellow 2.004 P 21 /n Protactinocene Pa(C8 H8 )2 Pa 1974 yellowish 1.933 (calculated)[ 3] P 21 /n Uranocene U(C8 H8 )2 U 1968 deep green 1.926 P 21 /n Neptunocene Np(C8 H8 )2 Np 1970 yellow-brown 1.909 P 21 /n Plutonocene Pu(C8 H8 )2 Pu 1970 dark red 1.898 I 2/m Berkelocene[ note 1] Bk(C14 H16 )2 Bk 2025 indigo 1.88 P 1
The most studied actinocene is uranocene, U(C8 H8 )2 , which in 1968 was the first member of this family to be synthesised and is still viewed as the archetypal example.[ 2] [ 5] [ 6] 8 H8 )2 ), thorocene[ 7] 8 H8 )2 ), neptunocene[ 8] 8 H8 )2 ), and plutonocene[ 9] [ 10] 8 H8 )2 ). Especially the latter two, neptunocene and plutonocene, have not been extensively studied experimentally since the 1980s because of theradiation hazard they pose.[ 9] [ 10] [ 11]
The actinide-cyclooctatetraenylbonding has been of interest for multiple theoretical studies.[ 10] [ 12] Computational chemistry methods indicate bonding with a largecovalent 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.[ 12] donation of electron density to the actinide. This donation is notably reduced in berkelocene relative to other characterized actinocenes, due to the stable 5f7 electron configuration of Bk4+ .[ 11]
Analogous sandwiched M(C8 H8 )2 compounds also exist forlanthanides M =Nd ,Tb , andYb , but therein the bonding ismostly ionic rather than covalent (seelanthanocenes ).[ 5]
^ Berkelocene was prepared with an annulated COT ligand, hexahydrodicyclopenta[8]annulene (hdcCOT); its properties are not strictly comparable to the other COT-ligated actinocenes in this table, but rather those also prepared with hdcCOT.[ 4] ^ 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 . ^a b Greenwood, Norman N.; Earnshaw, Alan (1997).Chemistry of the Elements . Butterworth-Heinemann. pp. 1278– 1280.ISBN 978-0-08-037941-8 ^ Kerridge, Andrew (2014)."f-Orbital covalency in the actinocenes (An = Th–Cm): multiconfigurational studies and topological analysis" .RSC Adv .4 (24). Royal Society of Chemistry (RSC):12078– 12086.doi :10.1039/c3ra47088a ISSN 2046-2069 . ^ Russo, Dominic R.; Branson, Jacob A.; Kelly, Sheridon N.; Sen, Asmita; Gunther, S. Olivia; Peterson, Appie; Smith, Patrick W.; Ouellette, Erik T.; Arnold, John; Autschbach, Jochen; Minasian, Stefan G. (2025-02-04)."Synthesis and characterization of isostructural annulated actinocenes" Chemical Communications .61 (12):2504– 2507.doi :10.1039/D4CC06094F .ISSN 1364-548X . ^a b 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 ^ Goffart, J.; Fuger, J.; Brown, D.; Duyckaerts, G. (1974-05-01)."On the cyclooctatetraenyl compounds of actinide elements part II. Bis-(cyclooctatetraenyl) protactinium(IV)" Inorganic and Nuclear Chemistry Letters .10 (5):413– 419.doi :10.1016/0020-1650(74)80119-4 .ISSN 0020-1650 . ^ 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 . ^ De Ridder, D. J. A.; Rebizant, J.; Apostolidis, C.; Kanellakopulos, B.; Dornberger, E. (1996-03-15)."Bis(cyclooctatetraenyl)neptunium(IV)" Acta Crystallographica Section C: Crystal Structure Communications .52 (3):597– 600.doi :10.1107/S0108270195013047 .ISSN 0108-2701 . ^a b 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.; Hobart, David E.; Huffman, Zachary K.; Huh, Daniel N. (2020-09-21)."A Single Small-Scale Plutonium Redox Reaction System Yields Three Crystallographically-Characterizable Organoplutonium Complexes" .Inorganic Chemistry .59 (18):13301– 13314.doi :10.1021/acs.inorgchem.0c01671 .ISSN 0020-1669 .OSTI 1680020 .PMID 32910649 .S2CID 221623763 . ^a b c Apostolidis, Christos; Walter, Olaf; Vogt, Jochen; Liebing, Phil; Maron, Laurent; Edelmann, Frank T. (2017-04-24)."A Structurally Characterized Organometallic Plutonium(IV) Complex" .Angewandte Chemie International Edition .56 (18):5066– 5070.doi :10.1002/anie.201701858 .PMC 5485009 PMID 28371148 . ^a b Russo, Dominic R.; Gaiser, Alyssa N.; Price, Amy N.; Sergentu, Dumitru-Claudiu; Wacker, Jennifer N.; Katzer, Nicholas; Peterson, Appie A.; Branson, Jacob A.; Yu, Xiaojuan; Kelly, Sheridon N.; Ouellette, Erik T.; Arnold, John; Long, Jeffrey R.; Lukens, Wayne W.; Teat, Simon J. (2025-02-28)."Berkelium–carbon bonding in a tetravalent berkelocene" Science .387 (6737):974– 978.doi :10.1126/science.adr3346 . ^a b Kerridge, Andrew (2014)."f-Orbital covalency in the actinocenes (An = Th–Cm): multiconfigurational studies and topological analysis" (PDF) .RSC Advances 4 (24):12078– 12086.Bibcode :2014RSCAd...412078K .doi :10.1039/C3RA47088A
