Reduction chemistry of the mixed ligand metallocene [(C5Me5)(C8H8)U]2(μ-C8H8) with bipyridines

The U4+ cyclooctatetraenyl complex, [(C5Me5)(C8H8)U](2)(mu-C8H8), 1, reacts with two equiv of 4, 4'-dimethyl-2,2'-bipyridine (Me(2)bipy) and 2 equiv of 2,2'-bipyridine (bipy) to form 2 equiv of (eta(5)-C5Me5)(eta(8)-C8H8)U(Me(2)bipy-kappa N-2,N') and (eta(5)-C5Me5)(eta(8)-C8H8)U(bipy-kappa N-2,N'), respectively. X-ray crystallography, infrared spectroscopy, and density functional theory calculations indicate that the products are best described as U4+ complexes of bipyridyl radical anions. Hence, only one of the (C8H8)(2) ligands in 1 acts as a reductant and delivers 2 electrons per equiv of 1. Since the reduction potentials of uncomplexed (C8H8)(2), Me(2)bipy, and bipy are -1.86, -2.15, and -2.10 V vs SCE, respectively, it is likely that prior coordination of the bipyridine reagents enhances the electron transfer. (C) 2010 Elsevier B.V. All rights reserved.