Low‐valent uranium‐element multiple bond complexes remain scarce, though there is burgeoning interest regarding to their bonding and reactivity. Herein, isolation of a uranium(III)‐carbon double bond complex [(Cp*)2U(CDP)](BPh4) (1) comprising a tridentate carbodiphosphorane (CDP) was reported for the first time. Oxidation of 1 afforded the corresponding U(IV) complex [(Cp*)2U(CDP)](BPh4)2 (2). The distance between U and C in 2 is 2.481 Å, indicating the existence of a typical U=C double bond, which is further confirmed by quantum chemical calculations. Bonding analysis suggested that the CDP also serves as both σ‐ and π‐donor in complex 1, though a longer U−C bond (2.666(3) Å) is observed. It implies that 1 is the first isolable mononuclear uranium(III) carbene complex. Moreover, these results suggest that CDPs are promising ligands to establish other low‐valent f‐block metal‐carbon multiple bond complexes.

Density functional theory calculations have been performed to gain insights into the catalytic mechanism of the N-quaternized pyridoxal (i.e., 1a)-mediated biomimetic asymmetric Mannich reaction of tert-butyl glycinate 3 with N-diphenylphosphinyl imine 2a to give the diamino acid ester 4a in high yield with excellent enantiomeric and diastereomeric selectivity (Science 2018, 360, 1438). The study reveals that the whole catalysis can be characterized via three stages: (i) the catalyst 1a reacts with the tert-butyl glycinate 3 to generate the active carbanion complex IM3. (ii) IM3 then reacts with the N-diphenylphosphinyl imine 2a giving the imine intermediate IM8. (iii) IM8 undergoes hydrolysis to give the final product anti-4a and regenerate the catalyst 1a for the next catalytic cycle. Each stage is kinetically and thermodynamically feasible for experimental realization. The hydrolysis step in the stage III is predicted to be the rate-determining step during the whole catalytic cycle. Furthermore, the origins of the enantioselectivity and diastereoselectivity for the target reaction, as well as the deactivation of the catalyst 1b, are also discussed.