Crystal structure of [Co(NH(3))(6)][Co(CO)(4)](2)

Hexaamminecobalt(II) bis­[tetra­carbonyl­cobaltate(-I)], [Co(NH(3))(6)][Co(CO)(4)](2), was synthesized by reaction of liquid ammonia with Co(2)(CO)(8). The Co(II) atom is coordinated by six ammine ligands. The resulting polyhedron, the hexa­amminecobalt(II) cation, exhibits point group symmetry -3. The Co(-I) atom is coordinated by four carbonyl ligands, leading to a tetra­carbonyl­cobaltate(−I) anion in the shape of a slightly distorted tetra­hedron, with point group symmetry 3. The crystal structure is related to that of high-pressure BaC(2) (space group R-3m), with the [Co(NH(3))(6)](2+) cations replacing the Ba sites and the [Co(CO)(4)](−) anions replacing the C sites. N—H⋯O hydrogen bonds between cations and anions stabilize the structural set-up in the title compound.