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Abstract:
Ba-5[CrN4]N is prepared by reaction of mixtures of Li3N, Ba3N2 and
CrN/Cr2N (1:1) (molar ratio Li:Ba:Cr = 3:5:1) in tantalum crucibles at
700 degrees C with flowing nitrogen (1 atm) within a period of 48 h.
After cooling down to room temperature (60 degrees C/h) black-shining
single crystals of the ternary phase with a platy habit are obtained
(monoclinic, C2/m; a = 1054.0(2)pm, b = 1170.9(3)pm, c = 937.7(2)pm beta
= 110,79(2)degrees; Z = 4). The crystal structure contains isolated
complex anions [(CrN4)-N-v](7-) which nearly satisfy the ideal
tetrahedral symmetry (Cr-N [pm]: 2 x 175.3(4), 2 x 175.8(5); NCr-N-N
[degrees]: 106.8(2), 109.5(2), 2 x 109.9(2), 2 x 110,3(2)). The
coordination sphere for each of the terminal nitride functions of the
complex anions is completed by five neighbouring Ba2+ ions (distorted
CrBa5 octahedra). The octahedra are connected via common CrBa2 faces as
well as CrBa edges thereby forming condensed tetrameric octahedral
groups. The isolated nitride ions which are also present in the crystal
structure of Ba-5[CrN4]N are in an octahedral environment of Ba2+ ions.
The presence of a d(1)-System (Cr(V)) is confirmed by magnetic
susceptibility data.
