Coordination of N-Donor Ligands to a Uranyl(V) β-Diketiminate Complex

Addition of 2 equiv of AgOTf to [UO2(Ar2nacnac)Cl]2 (Ar2nacnac = {(2,6-Pri2C6H3)NC(Me)}2CH) in the presence of excess pyridine, followed by addition of Cp2Co, generates the uranyl(V) complex UO2(Ar2nacnac)(py)2 (2), in moderate yield. Complex 2 has proven to be an excellent precursor for the synthesis of other U(V) complexes. Thus, addition of 2,2′-bipyridine (bipy), 1,10-phenanthroline (phen), TMEDA, or 1-methylimidazole (MeIm) to 2 provides UO2(Ar2nacnac)(bipy) (3), UO2(Ar2nacnac)(phen) (4), UO2(Ar2nacnac)(TMEDA) (5), and UO2(Ar2nacnac)(MeIm)2 (6), respectively. Complexes 2−6 have been fully characterized and their structures confirmed by X-ray crystallography. Attempts to form the analogous hexavalent uranyl complexes of bipy, phen, and TMEDA have not been successful. However, reaction of [UO2(Ar2nacnac)Cl]2 with AgOTf and 2 equiv of MeIm leads to the isolation of [UO2(Ar2nacnac)(MeIm)2][OTf] (7), which has been fully characterized. Attempts to ligate sulfur donor ligands to either the UO2(Ar2nacnac) or the [UO2(Ar2nacnac)]+ fragments were unsuccessful.