The reaction of 3 equiv of Li-C6H3-2,6-(C6H4-4-Bu-t)(2) (Terph-Li) with UI3(1,4-dioxane)(1.5) led to the formation of the homoleptic uranium(III) tris(aryl) complex (Terph)(3)U (1). The U-C bonds are reactive: treatment with excess (PrN)-Pr-i=C=(NPr)-Pr-i yielded the double-insertion product [TerphC((NPr)-Pr-i)(2)](2)U(Terph) (2). Complexes 1 and 2 were characterized by X- ray crystallography, which showed that the U-C bond length in 2 (2.624(4) angstrom) is similar to 0.1 angstrom longer than the average U-C bond length in 1 (2.522(2) angstrom). Thermal decomposition of 1 yielded Terph-H as the only identifiable product; the process is unimolecular with activation parameters Delta H double dagger = 21.5 +/- 0.3 kcal/mol and Delta S double dagger = -7.5 +/- 0.8 cal.mol(-1) K-1, consistent with intramolecular proton abstraction. The protonolysis chemistry of 1 was also explored, which led to the uranium(IV) alkoxide complex U(OCPh3)(4)(DME) (3 center dot DME).