Formation of a Uranium-Bound η1‑Cyaphide (CP–) Ligand via Activation and C–O Bond Cleavage of Phosphaethynolate (OCP–)

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.