Influence of the 1,2,4-Tri-tert-butylcyclopentadienyl Ligand on the Reactivity of the Uranium Bipyridyl Metallocene [η5-1,2,4-(Me3C)3C5H2]2U(bipy)

The uranium bipyridyl metallocene, [eta 5-1,2,4-(Me3C)3C5H2]2U(bipy) (2), prepared from [eta 5-1,2,4-(Me3C)3C5H2]2UCl2 (1) and 2,2 '-bipyridine in the presence of potassium graphite (KC8) has been evaluated in small-molecule activation. In contact with AgF, Ph2E2 (E = S, Se), (PhNH)2, (PhCH=N)2, diazenes, pyridine N-oxide, organic azides, diazoalkanes, Ph2CS, and Ph2CO, it behaves as a synthon for the [eta 5-1,2,4-(Me3C)3C5H2]2U(II) fragment. In contrast, C-C bond coupling occurs when 2 is treated with (CH2)5CO, p-MePhCHO, and p-ClPhCHO to furnish [eta 5-1,2,4-(Me3C)3C5H2]2U[(bipy){(CH2)5CO}] (19), [eta 5-1,2,4-(Me3C)3C5H2]2U[(bipy)(p-MePhCHO)] (20), and [eta 5-1,2,4-(Me3C)3C5H2]2U[(bipy)(p-ClPhCHO)] (21), respectively. Moreover, a single-electron transfer (SET) process ensues after the addition of CuI to 2 to yield the uranium(III) iodide complex [eta 5-1,2,4-(Me3C)3C5H2]2UI (3). A comparison with the other uranium bipyridyl metallocene derivatives shows that minor variations in the coordinated cyclopentadienyl ligands changes the reactivity of these compounds.