Small-Molecule Activation Mediated by a Uranium Bipyridyl Metallocene

Addition of potassium graphite (KC8) to a solution of (eta(5)-C5Me5)(2)UCl2 (1) and 2,2'-bipyridine (bipy) gives the uranium bipyridyl metallocene (eta(5)-C5Me5)(2)U(bipy) (2) in good yield. In complex 2 a bipy radical anion is coordinated to a U(III) atom, and it is therefore an ideal starting material for small-molecule activation: e.g., it serves as a synthetic equivalent for the (eta(5)-C5Me5)(2)U-II fragment on treatment with conjugated alkynes and a variety of heterounsaturated molecules such as imines, carbodiimide, organic azides, hydrazine, and azo derivatives. Alternatively, it may also react with aldehydes, ketones, nitriles, and alpha,beta-unsaturated reagents such as p-ClPhCHO, (CH2)(5)CO, PhCN, and methyl methacrylate (MMA), forming the C-C bond coupling products (eta(5)-C5Me5)(2)U[(bipy) (p-ClPhCHO)] (10), (eta(5)-C5Me5)(2)U[bipy){(CH2)(5)CO}] (11), (eta(5)-C5Me5)(2)U[bipy)(PhCN)] (12), (eta(5)-C5Me5)(2)U[(bipy)CH2=C(Me)CO(OMe)] (13a), and {(eta(5)-C5Me5)(2)U{OC(OMe)=C(Me)CH2-3-bipy}](2) (13b), respectively, in quantitative conversion. Furthermore, addition of CuI to complex 2 induces a single -electron -transfer process to form the uranium(III) iodide complex (eta(5)-C5Me5)(2)U(I)(bipy) (14).