Reactivity of uranium(IV) bridged chalcogenido complexes UIV–E–UIV (E = S, Se) with elemental sulfur and selenium: synthesis of polychalcogenido-bridged uranium complexes

We report the syntheses, electronic properties, and molecular structures of a series of polychalcogenido-bridged dinuclear uranium species. These complexes are supported by the sterically encumbering but highly flexible, single N-anchored tris(aryloxide) chelator (AdArO)3N3−. Reaction of an appropriate uranium precursor, either the U(III) starting material, [((AdArO)3N)U(DME)], or the dinuclear mono-chalcogenido-bridged uranium(IV/IV) compounds [{((AdArO)3N)U(DME)}2(μ-E)] (E = S, Se), with elemental sulfur or selenium, yields new complexes with a variety of bridging chalcogenide entities μ-Emn− (E = S, m = 2, n = 1 or 2 and E = Se, m = 2, 4; n = 2). Activation of the heavy chalcogens typically requires either a coordinatively unsaturated, strongly-reducing metal complex or a compound with a metal–metal bond. Since uranium complexes in the +IV oxidation state, are generally considered rather unreactive, the observed reaction of the here employed uranium(IV)/(IV) species with elemental chalcogens is fairly remarkable