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Zusammenfassung:
Ba2(Ni1-xLix)Ni2N2 is obtained by reaction of lithium-barium-melts
(molar ratios Li:Ba between 1:1 and 3:1) with nitrogen (1 atm.) in
nickel-crucibles within a period of 15 h. Single crystals with a
dark-metallic lustre are formed by cooling the melt to room temperature
with a rate of 10-degrees-C/h (orthorhombic, Cmca; a = 713.3(2) pm, b =
1027.4(7) pm, c = 752.2(4) pm; Z = 4; D(XR) = 5.50 g/cm3 with x = 0.43).
The crystal structure contains nearly linear 1 infinity [NiN2/2]-chains
(N-Ni-N: 178.5(7)-degrees, Ni-N-Ni 173.4(7)-degrees; Ni-N: 178.6(1)
pm), running parallel to the [100] direction, which are interconnected
via (Ni1-xLi(x))-sites (linear units (N-(Ni1-xLix)-N); bond-lenths:
194.5(12) pm with x = 0.43) to form puckered layers 2 infinity
[(NiN2/2)-(Ni1-xLix)-(NiN2/2)]. Barium is in a distorted
trigonal-planar coordination by nitrogen atoms (Ba-N: 281.1(11) pm -
285.5(11) pm). The nitrogen-coordination corresponds to a distorted
octahedron, NBa3(Ni1-xLix)Ni2, with nickel in trans-position.
The crystal structure of Ba2(Ni1-xLix)Ni2N2 is closely related to the
Li3N-type structure: Li2[LiN] <--> Ba{(Ni1-xLix)0.5-square-0.5}[NiN].
Furthermore, this structure enlarges the scope of
barium-nitrido-niccolates which up to now were found to contain merely 1
infinity [NiN2/2]-chains (BaNiN: planar zigzag-chains; Ba8Ni6N7:
helical zigzag-chains)
