2019/11/14 by Josef T. Boronski, Laurence R. Doyle, John A. Seed +2 · 1 citation
Chemistry · #Radioactive element chemistry and processing #Organometallic Complex Synthesis and Catalysis #Coordination Chemistry and Organometallics
paper · doi:10.1002/anie.201913640
openalex publication_date 2019/11/14 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/02
Abstract Despite there being numerous examples of f‐element compounds supported by cyclopentadienyl, arene, cycloheptatrienyl, and cyclooctatetraenyl ligands (C 5–8 ), cyclobutadienyl (C 4 ) complexes remain exceedingly rare. Here, we report that reaction of [Li 2 C 4 (SiMe 3 ) 4 (THF) 2 ] ( 1 ) with [U(BH 4 ) 3 (THF) 2 ] ( 2 ) gives the pianostool complex [UC 4 (SiMe 3 ) 4 (BH 4 ) 3 ][Li(THF) 4 ] ( 3 ), where use of a borohydride and preformed C 4 ‐unit circumvents difficulties in product isolation and closing a C 4 ‐ring at uranium. Complex 3 is an unprecedented example of an f‐element half‐sandwich cyclobutadienyl complex, and it is only the second example of an actinide‐cyclobutadienyl complex, the other being an inverse‐sandwich. The U−C distances are short (av. 2.513 Å), reflecting the formal 2− charge of the C 4 ‐unit, and the SiMe 3 groups are displaced from the C 4 ‐plane, which we propose maximises U−C 4 orbital overlap. DFT calculations identify two quasi‐degenerate U−C 4 π‐bonds utilising the ψ 2 and ψ 3 molecular orbitals of the C 4 ‐unit, but the potential δ‐bond using the ψ 4 orbital is vacant.