SYNTHESIS AND CRYSTAL-STRUCTURE OF A NEW MODIFICATION OF TETRASELENIUM TETRANITRIDE, SE4N4

Beta-Se4N4 has been prepared by the reaction of selenium dioxide with the phosphane imine Me3SiNPMe3 in acetonitrile, forming red-brown crys tal needles. The crystal structure analysis shows a new modification, the IR spectrum of which differs only slightly from the known alpha-fo rm of Se4N4 (space group C2/c). Beta-Se4N4: Space group P2(1)/n, Z = 4 , structure solution with 1 667 observed unique reflections, R = 0.054 . Lattice dimensions at -50-degrees-C: a = 881.8(2), b = 738.7(2), c = 899.6(2) pm, beta = 93.58(1)-degrees. Just as the alpha-form beta-Se4 N4 forms cage molecules without symmetry and intramolecular Se-Se cont acts of 273.2 and 274.0 pm. There are strong Se ... N-interactions bet ween the Se4N4 molecules.