Uranium carbon multiple-bond chemistry. 3. Insertion of acetonitrile and the formation of a uranium nitrogen multiple bond

Dark red crystals of CpUNCH(CH/sub 3/)CHP(CH/sub 3/.C/sub 6/H/sub 5/CH/sub 3/ were grown in a mixture of toluene and heptane (CP is cyclopentadienyl-). Spectral data were inconclusive so crystal structure was determined by x-ray diffraction. The structure was routinely solved by Patterson and Fourier methods. An OPTEP drawing of the molecule is shown. The crystals belong to the triclinic space group. Lattice parameter, bond lengths, and bond angles are listed. The acetonitrile has been inserted into the U-C bond of the starting compound to form an NC(CH/sub 3/)CHP(C/sub 6/H/sub 5/)/sub 2/CH/sub 3/ ligand that coordinates through nitrogen. The U-N bond distance, 2.06 (1) angstrom, is the shortest the authors have seen reported. Such a short bond indicates multiple bond character; nitrogen might be able to donate as many as 3 electron pairs to uranium.