Actinide tetra-N-heterocyclic carbene 'sandwiches'.
- Author(s): DeJesus, Joseph F;
- Kerr, Ryan WF;
- Penchoff, Deborah A;
- Carroll, Xian B;
- Peterson, Charles C;
- Arnold, Polly L;
- Jenkins, David M
- et al.
Published Web Locationhttps://doi.org/10.1039/d1sc01007g
Highly-symmetrical, thorium and uranium octakis-carbene 'sandwich' complexes have been prepared by 'sandwiching' the An(iv) cations between two anionic macrocyclic tetra-NHC ligands, one with sixteen atoms and the other with eighteen atoms. The complexes were characterized by a range of experimental methods and DFT calculations. X-ray crystallography confirms the geometry at the metal centre can be set by the size of the macrocyclic ring, leading to either square prismatic or square anti-prismatic shapes; the geometry of the latter is retained in solution, which also undergoes reversible, electrochemical one-electron oxidation or reduction for the uranium variant. DFT calculations reveal a frontier orbital picture that is similar to thorocene and uranocene, in which the NHC ligands show almost exclusively σ-donation to the metal without π-backbonding.