(OLI2CA4)(3)[MN4](4) (M=MO, W) - NITRIDOMETALATE OXIDES WITH CLOSE STRUCTURAL RELATIONSHIPS TO THE TH3P4 TYPE-STRUCTURE

Molybdenum and tungsten powder react readily with alkali and alkaline earth metal nitrides to form nitridometalates. Transparent yellow sing le crystals of the title compounds are formed in the presence of trace s of oxides under flowing nitrogen at 850 degrees C/900 degrees C. The crystal structures were determined by single crystal X-ray analyses ( space group I (4) over bar 3d, Z = 4, (OLi2Ca4)(3)[MoN4](4): a = 13.06 1(3) Angstrom, (OLi2Ca4)(3)[WN4](4): a = 13.060(2) Angstrom). Predomin ant structural features are isolated tetrahedral complex anions [MoN4] (6-) and [WN4](6-), which can be described in accordance with the exte nded Zintl-Klemm concept. The isolated oxygen atoms are surrounded by four Ca and two Li cations in a tetragonal bipyramidal arrangement wit h Ca forming the tetragonal basis. The centers of tetrahedra and tetra gonal bipyramids form a pattern which resembles the motif of the Th3P4 type structure.