LI3SR3NI4N4 - AN LOW-VALENCY NITRIDONICCOLATE WITH 1-INFINITY-[NIN]-CHAINS

Isometric black-reflecting crystals of Li3Sr3Ni4N4 (orthorhombic, Immm; a = 401.1(1) pm, b = 708.8(3) pm, c = 1663.0(8) pm; Z = 2) were obtained by wall-reaction of Li4SrN2 in closed nickel tubes (heating rate 50-degrees-C/h; reaction at 800-degrees-C for 20 h; cooling rate 10-degrees-C/h). The crystal structure contains infinity 1 [NiN]-chains (Ni-N: 177.3(1) and 177.8(1) pm) which run parallel to the [010] direction. Lithium and strontium are arranged in planes (010) perpendicular to the [NiN]-chains and interconnect the chains via the nitrogen atoms. Lithium is in a two-fold (linear; Li-N: 200.7(1) pm and 200.4(7) pm), strontium is in three- and four-fold (distorted trigonal- and square-planar) N-coordination (Sr-N: 264.5(5) pm, 268.0(7) pm and 277.6(6) pm, resp.). Nitrogen is in an octahedral surrounding by Ni, Li and Sr; the coordination-octahedra NNi2Sr4 and NNi2Li3Sr are condensed by sharing common edges and apices. The three-dimensional framework contains one-dimensional fragments of the (inverse) octahedral structures of the ReO3 and Rutile structure types.