The UC Double Bond: Synthesis and Study of Uranium Nucleophilic Carbene Complexes

Treatment of U(BH4)4 with 1 or 3 equiv of Li2(SCS)·1.5Et2O, 1, afforded the actinide carbene complexes U(μ-SCS)3[U(BH4)3]2 (4) and U(μ-SCS)3[Li(Et2O)]2 (6), respectively [SCS = (Ph2P = S)2C]. In THF, complex 4 was transformed into the mononuclear derivative (SCS)U(BH4)2(THF)2 (5). The multiple bond character of the uranium−carbon bond was first revealed by the X-ray crystal structures of the three complexes. The UC bond in these complexes present a nucleophilic character, as shown by their reaction with a carbonyl derivative. Finally, DFT calculations prove the involvement of both 5f and 6d orbitals in both the σ and the π U−C bonds.