Synthesis, Crystal Structure, Bonding, and Properties of (Ba6O)(OsN3)2

The new barium nitridoosmate oxide (Ba6O)(OsN3)(2) was prepared by reacting elemental barium and osmium (3:1) in nitrogen at 815-830 degrees C. The crystal structure of (Ba6O)-(OsN3)(2) as determined by laboratory powder X-ray diffraction (R (3) over bar, No 148: a=b=8.112(1) angstrom, c =17.390(1) angstrom, V=991.0(1) angstrom(3), Z=3), consists of sheets of trigonal OsN3 units and trigonal-antiprismatic Ba6O groups, and is structurally related to the "313 nitrides" AE(3)MN(3) (AE=Ca, Sr, Ba, M=V-Co, Ga). Density functional calculations, using a hybrid functional, likewise indicate the existence of oxygen in the Ba-6 polyhedra. The oxidation state 4+ of osmium is confirmed, both by the calculations and by XPS measurements. The bonding properties of the OsN35- units are analyzed and compared to the Raman spectrum. The compound is paramagnetic from room temperature down to T=10 K. Between room temperature and 100 K it obeys the Curie-Weiss law (mu = 1.68 mu(B)). (Ba6O)(OsN3)(2) is semiconducting with a good electronic conductivity at room temperature (8.74 x 10(-2) Omega(-1)cm(-1)). Below 142 K the temperature dependence of the conductivity resembles that of a variable-range hopping mechanism.