Reaction of the trivalent uranium complex [((Ad,MeArO)3N)­U­(DME)] with [Na­(OCP)­(dioxane)2.5] and 2.2.2-crypt yields the μ-oxo-bridged, diuranium complex [Na­(2.2.2-crypt)]­[{((Ad,MeArO)3N)­U­(DME)}­(μ-O)­{((Ad,MeArO)3N)­U­(CP)}] (1). Complex 1 features an asymmetric, dinuclear UIV–O–UIV core structure with a cyaphide (CP–) anion η1-CP bound to one of the U ions, and a κ2-O DME coordinated to the other. The CP– ligand is unprecedented in uranium chemistry and is formed through reductive C–O bond cleavage of the phosphaethynolate anion (OCP–). An analogous reaction was performed starting from the tetravalent uranium halide complex [((Ad,MeArO)3N)­U­(DME)­(Cl)]. This salt metathesis approach with [Na­(OCP)­(dioxane)2.5] results in formation of the mononuclear complex [((Ad,MeArO)3N)­U­(DME)­(OCP)] (2) with an OCP– anion bound to the uranium­(IV) center via the oxygen atom in an η1-OCP fashion.

Despite their importance as mechanistic models for heterogeneous Haber Bosch ammonia synthesis from dinitrogen and dihydrogen, homogeneous molecular terminal metal-nitrides are notoriously unreactive towards dihydrogen, and only a few electron-rich, low-coordinate variants demonstrate any hydrogenolysis chemistry. Here, we report hydrogenolysis of a terminal uranium(V)-nitride under mild conditions even though it is electron-poor and not low-coordinate. Two divergent hydrogenolysis mechanisms are found; direct 1,2-dihydrogen addition across the uranium(V)-nitride then H-atom 1,1-migratory insertion to give a uranium (III)-amide, or with trimesitylborane a Frustrated Lewis Pair (FLP) route that produces a uranium(IV)-amide with sacrificial trimesitylborane radical anion. An isostructural uranium (VI)-nitride is inert to hydrogenolysis, suggesting the 5f 1 electron of the uranium(V)-nitride is not purely non-bonding. Further FLP reactivity between the uranium(IV)-amide, dihydrogen, and triphenylborane is suggested by the formation of ammonia-triphenylborane. A reactivity cycle for ammonia synthesis is demonstrated, and this work establishes a unique marriage of actinide and FLP chemistries.