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Abstract:
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.
