Crystal structure of an unknown solvate of bis­(tetra-n-butyl­ammonium) [N,N′-(4-tri­fluoro­methyl-1,2-phenyl­ene)bis­(oxamato)-κ(4) O,N,N′,O′]nickelate(II)

In the title compound, [N(C(4)H(9))(4)](2)[Ni(C(11)H(3)F(3)N(2)O(6))] or [N(n-Bu)(4)](2)[Ni(topbo)] [n-Bu = n-butyl and topbo = 4-tri­fluoro­methyl-1,2-phenyl­enebis(oxamate)], the Ni(2+) cation is coordinated by two deprotonated amido N atoms and two carboxyl­ate O atoms, setting up a slightly distorted square-planar coordination environment. The [Ni(topbo](2−) anion lies on a twofold rotation axis. Due to an incompatibility with the point-group symmetry of the complete mol­ecule, orientational disorder of the CF(3) group is observed. The tetra­hedral ammonium cations and the anion are linked by weak inter­molecular C—H⋯O and C—H⋯F hydrogen-bonding inter­actions into a three-dimensional network. A region of electron density was treated with the SQUEEZE procedure in PLATON [Spek (2015). Acta Cryst. C71, 9–18] following unsuccessful attempts to model it as plausible solvent mol­ecule(s). The given chemical formula and other crystal data do not take into account the unknown solvent mol­ecule.