Complex Featuring Two Double Dative Bonds Between Carbon(0) and Uranium

The uranyl with two U=O double bonds is a well-known and predominant form of uranium in the environment, but the carbon-based analog with two U=C double bonds has rarely been synthesized. Here, we describe the formation of an unprecedented uranium complex [(PyPh₂P)₂C]₂UCl₂]²⁺·2(BPh₄⁻) from the reaction of UCl₄ with carbodiphosphorane in the presence of NaBPh₄. The nature of the U–C bonds was revealed by density functional theory calculations, which show that the 5f and 6d orbital electrons of uranium are remarkably involved in the U=C double bonds. The inspection of the bonding characteristics with an energy decomposition analysis suggests that the uranium-ligand bond may be alternatively described with double dative bonds [CUC] or strong electron-sharing π bonds and weak σ bonds.