Heteroleptic Actinocenes: A Thorium(IV)-CyclobutadienylCyclooctatetraenyl-Di-Potassium-Cyclooctatetraenyl Complex

Josef Boronski, Ashley Wooles, Stephen Liddle

Research output: Contribution to journalArticlepeer-review


Despite the vast array of hn-carbocyclic C5-8 complexes reported for actinides, cyclobutadienyl (C4) remain exceedingly rare, being restricted to six uranium examples. Here, overcoming the inherent challenges of installing highly reducing C4-ligands onto actinides when using polar starting materials such as halides, we report that reaction of [Th(η8-C8H8)2] with [K2{C4(SiMe3)4}] gives [{Th(η4-C4[SiMe3]4)(µ-η8-C8H8)(µ-η2-C8H8)(K[C6H5Me]2)}2{K(C6H5Me)}{K}] (1), a new type of heteroleptic actinocene. Quantum chemical calculations suggest that the thorium ion engages in p- and d-bonding to the h4-cyclobutadienyl and h8-cyclooctatetraenyl ligands, respectively. Furthermore, the coordination sphere of this bent thorocene analogue is supplemented by an h2-cyclooctatetraenyl interaction, which calculations suggest is composed of sand p-symmetry donations from in-plane in- and out-of-phase C=C 2p-orbital combinations to vacant thorium 6d orbitals. The characterisation data are consistent with this being a metal-alkene-type interaction that is is integral to the bent structure and stability of this complex.
Original languageEnglish
JournalChemical Science
Publication statusAccepted/In press - 10 Jun 2020


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