Synthesis and Reactivity of Terminal U(IV) Hydrides Including the Isolation of a κ¹-Formate

Formation of a rare terminal U(IV) hydride complex, [(C5Me5)2(2,6-tBu2-4-MeC6H2O)U(H)], was accomplished through the hydrogenation of a uranium(IV) metallocene hydrocarbyl complex. The reactivity of this hydride was probed with a variety of substrates to examine sigma-bond metathesis, PhEEPh (E = S, Se, Te), and insertion (CO2, CH2═CH2) reactivity. While the reaction of CO did not produce an isolable result, using the U(IV) hydride with a less sterically encumbering mesityl aryloxide, an ethenediolate is formed, [{(C5Me5)2(MesO)U}2(μ2-OC(H)═C(H)O], Mes = mesityl, 2,4,6-Me3C6H2. Each complex has been characterized by NMR, IR, and X-ray crystallographic analysis.