Uranium-stibinidiide, -stibinidene, and -stibido multiple bonds and uranium-nitride formation from multimetallic diuranium-distibene-mediated dinitrogen cleavage

Although uranium-nitrogen multiple bonding is well developed, there are far fewer uranium-phosphorus and -arsenic multiple bonds, and none for antimony, even in spectroscopic scenarios. Here, we report straightforward syntheses of uranium-stibido, -stibinidiide, -distibene, and -stibinidene derivatives containing single, double, and pseudo-triple bond interactions. Quantum chemical calculations suggest that these uranium-antimony multiple bonds are more covalent than thorium-antimony congeners, due to superior spatial and energy matching of uranium and antimony frontier orbitals, but comparison to isostructural uranium-phosphorus and -arsenic analogues suggests that for uranium moving from phosphorus to arsenic to antimony the spatial overlap term reduces but the orbital energy matching improves. Reduction of the distibene complex results in loss of the antimony-component and multimetallic activation and cleavage of dinitrogen to nitride. This constitutes an uncommon mode of reactivity for uranium that is co-facilitated by the distibene and potassium ions.