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

(C5Me4H)(3)U, 1, reacts with 1 equiv of NO to form the first f element nitrosyl complex (C5Me4H)(3)UNO, 2. X-ray crystallography revealed a 180 degrees U-N-O bond angle, typical for (NO)(1+) complexes. However, 2 has a 1.231(5) angstrom N=O distance in the range for (NO)(1-) complexes and a short 2.013(4) angstrom 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 pi interactions between uranium 5f orbitals and NO pi* 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 mu(B) at room temperature. Complex 2 reacts with Al2Me6 to form the adduct (C5Me4H)(3)UNO(AlMe3), 3.