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

Abstract

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.