Diuranium Inverted Sandwiches Involving Naphthalene and Cyclooctatetraene

Treatment of IU(DME)(NC[tBu]Mes)3 (2-I-DME) with 4 equiv of KC8 and 0.5 equiv of naphthalene in DME allowed the isolation of a naphthalene-bridged compound, K2(μ-η6,η6-C10H8)[U(NC[tBu]Mes)3]2 (K2-22-μ-C10H8), in 60% yield as a dark brown powder. The twelve U−C distances are rather short, varying from 2.565(11) to 2.749(10) Å. Treatment of M2-22-μ-C10H8 (M = Na, K) with 2 equiv of 1,3,5,7-cyclooctatetraene afforded a mixture of two products:  M-2-COT and 22-μ-COT. Compound 22-μ-COT can be assembled independently in 90% yield by salt elimination upon reaction of M-2-COT with iodide 2-I-DME. The U−Carene distance in compound 22-μ-COT is longer than that in its naphthalene counterpart K2-22-μ-C10H8 (2.822 vs 2.634 Å), in accord with bonding considerations. A DFT study performed on model compounds for both M2-22-μ-C10H8 and 22-μ-COT indicates that the δ bonds present in the former compound show better covalent overlap.