Ba2(Ni1-xLix)Ni2N2: a low-valency nitridoniccolate with puckered layers ∞2[(NiN2/2)-(Ni1-xLix)-(NiN2/2)]

Ba2(Ni1-xLix)Ni2Ni2 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 10degC/h (orthorhombic, Cmca; a = 713.3(2)pm, b = 1027.7(7)pm, c = 752.2(4)pm; Z = 4; DXR = 5.50 g/cm3 with x = 0.43). The crystal structure contains nearly linear ∞1[NiN2/2]-chains (N-Ni-N: 178.5(7)deg, Ni-N-Ni 173.4(7)deg, Ni-N: 178.6(1)pm), running parallel to the [100] direction, which are interconnected via (Ni1-xLix)-sites (linear units (N-(Ni1-xLix)-N); bond-lenths: 194.5(12)pm with x = 0.43) to form puckered layers ∞2[(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□0.5}[NiN]. Furthermore, this structure enlarges the scope of barium-nitrido-niccolates which up to now were found to contain merely ∞1[NiN2/2]-chains (BaNiN: planar zigzag-chains; Ba8Ni6N7: helical zigzag-chains). (orig.)