The uranyl with two U=O double bonds is a wellknown 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 [(PyPh 2 P) 2 C] 2 UCl 2 ] 2+ •2(BPh 4 − ) from the reaction of UCl 4 with carbodiphosphorane in the presence of NaBPh 4 . The nature of the U-C bonds was revealed by density functional theory calculations, which show that the 5f and 6d orbital

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... 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 [C⇉U⇇C] or strong electron-sharing π bonds and weak σ bonds.