A crystalline uranium Fischer-type carbyne

Abstract

Abstract Since their discovery in 1973, transition metal Fischer carbynes have become a foundational class of metal–carbon triple bond in organometallic chemistry. However, even though the uranium Fischer carbyne bonding motif has been a fundamental target in f -element chemistry, its isolation has remained challenging. Here we report the synthesis and characterization of the uranium Fischer-type carbyne complex [N″ 3 U(μ-CNN)UN″ 3 ] (N″ = N(SiMe 3 ) 2 ). Single-crystal X-ray diffraction analysis reveals a uranium–carbyne distance of 2.379(15) Å, and density functional theory calculations combined with experimental quantum crystallography Hirshfeld atom refinement reveal the presence of two-electron C→U σ -donation, weak two-electron C→U π -donations and two orthogonal one-electron U→C π -back-bonds, demonstrating σ 2 π 1 π 1 Fischer-type carbyne bonding overall. This work redefines the range of bonding modes for the diazomethanediide ligand and reveals a uranium–carbon triple-bond interaction that is related, yet distinct from transition metal Fischer carbynes, providing a basis to develop and understand f -element carbyne chemistry.