Synthesis, Structure, and Magnetism of an f Element Nitrosyl Complex, (C5Me4H)3UNO

(C5Me4H)3U, 1, reacts with 1 equiv of NO to form the first f element nitrosyl complex (C5Me4H)3UNO, 2. X-ray crystallography revealed a 180° U–N–O bond angle, typical for (NO)1+ complexes. However, 2 has a 1.231(5) Å NO distance in the range for (NO)1– complexes and a short 2.013(4) Å U–N bond like the UN bond of uranium imido complexes. Structural, spectroscopic, and magnetic data as well as DFT calculations suggest that reduction of NO by U3+ has occurred to form a U4+ complex of (NO)1– that has π interactions between uranium 5f orbitals and NO π* orbitals. These bonding interactions account for the linear geometry and short U–N bond. The complex displays temperature-independent paramagnetism with a magnetic moment of 1.36 μB at room temperature. Complex 2 reacts with Al2Me6 to form the adduct (C5Me4H)3UNO­(AlMe3), 3.