Lawrence Berkeley National Laboratory

The reactivity of two metallocene aryloxide U(III) complexes, [(C5Me5)2U(O-Ar)], Ar = 4-tBuC6H4, 1; Ar = 2,6-tBu2-4-CH3C6H2(BHT), 3, with CO2and CS2has been investigated. The reaction of 1 with CO2produces a bridging oxo complex, [{(C5Me5)2(4-tBuC6H4-O)U}2(μ2-O)], 4, while 3 with CO2results in reductive disproportionation to form the bridging carbonate species, [{(C5Me5)2(BHT)U}2(μ2-κ2:η1-CO3)], 5. The difference in reactivity can be attributed to the steric properties of the ligand because the reaction of 3 with an oxo-delivering agent yields a U(V) terminal oxo complex, [(C5Me5)2(BHT)U═O], 6. Reduction of CS2to form a bridging (CS2)2-ligand, [{(C5Me5)2(tBuC6H4-O)U}2(μ2-CS2)], 7, is observed with 1, while the reaction of 3 with CS2also produces a bridging (CS2)2-reduced ligand complex, followed by C-H bond activation of a methyl group from one (C5Me5)1-ring, [(C5Me5)2(BHT)U{μ2-C(H)S2}U(C5Me4CH2)(C5Me5)(BHT)], 8. All compounds are characterized by NMR and IR spectroscopy, and their solid-state structures are determined by X-ray crystallography.