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Abstract:
Molybdenum and tungsten powder react readily with alkali and alkaline
earth metal nitrides to form nitridometalates. Transparent yellow single
crystals of the title compounds are formed in the presence of traces 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 =
13.061(3) Angstrom, (OLi2Ca4)(3)[WN4](4): a = 13.060(2) Angstrom).
Predominant structural features are isolated tetrahedral complex anions
[MoN4](6-) and [WN4](6-), which can be described in accordance with the
extended Zintl-Klemm concept. The isolated oxygen atoms are surrounded
by four Ca and two Li cations in a tetragonal bipyramidal arrangement
with Ca forming the tetragonal basis. The centers of tetrahedra and
tetragonal bipyramids form a pattern which resembles the motif of the
Th3P4 type structure.
