BA[CON] - A LOW-VALENCY NITRIDOCOBALTATE WITH ANGLED CHAINS INFINITY[CON2/22-]

Ba[CoN] is prepared by reaction of barium and cobalt (molar ratio Ba:Co = 1:2.5) in tantalum crucibles at 870-degrees-C with flowing nitrogen (1 atm) within a period of 96 h. After cooling down to room temperature (24-degrees-C/h) black single crystals of the ternary phase with a platy habit are obtained (orthorhombic, Pnma; a = 959.9(2) pm, b = 2351.0(3) pm, c = 547.6(2) pm; Z = 20). The crystal structure of Ba[CoN] contains angled (planar) chains infinity1[CoN2/2(2-)] which run along the [010]-direction (N-Co-N[degree]: 178.5(5), 179.6(6), 180.0; Co-N-Co[degree]: 82.9(6), 84.2(5), 177.1(8); Co-N[pm]: 174.6(12), 177.2(12), 181.9(13), 184.3(13), 187.1(12)). Nitrogen is in an octahedral coordination (NBa4Co2) and is arranged in a distorted cubic close packing. Barium occupies one half of the tetrahedral holes (Ba-N[pm]: 274.8(16) - 308.2(12)). The cis-positions of the Co-atoms at the nitrogen coordination-octahedra cause short Co-Co contacts within the chains infinity1[CoN2/2(2-)]. Through this, Co2-units (Co-Co[pm]: 247.8(4); bridged by nitrogen) and linear Co3-groups (Co-Co [pm]: 245.5(2); Co-Co-Co[degree]: 180.0; bridged by nitrogen) alternate along the chains. The crystal structure of Ba[CoN] is closely related to the Ba[NiN] type structure.