Crystal Structure Determination of Thallium Carbodiimide, Tl₂NCN

Orange‐red single crystals of thallium carbodiimide, Tl 2 NCN, have been grown from an aqueous solution of cyanamide and thallium carbonate under strongly basic conditions. Tl 2 NCN crystallizes in space group with a = 5.338(1), b = 6.626(2), c = 9.645(3) Å, α = 98.765(4)°, β = 98.685(4)°, γ = 113.178(4)°, and Z = 3; the structure can be considered a strongly distorted anti ‐CdI 2 type. One finds two crystallographically different and irregular [NCN]Tl 6 octahedra in which the Tl–N distances of the three‐coordinate monovalent thallium ions lie between 2.52 and 2.72Å. The two symmetry‐inequivalent NCN 2− units adopt the carbodiimide shape, and the course of its molar volume as a function of the monovalent counter cation is analyzed.