Synthesis and crystal structure of ammine copper(I) cyanamide, Cu4(NCN)2NH3

Ammine copper(I) cyanamide, CU4(NCN)(2)NH3, was obtained as a white powder from the reaction between CuCl and H2NCN in concentrated ammonia solution. X-ray and neutron diffraction experiments yield the hexagonal system with space group P63mc (no. 186) and a = 5.7661(1) angstrom, c = 10.7817(3) angstrom, and Z = 2. The structure is characterized by layers of monovalent copper ions with an average Cu-Cu distance of 2.89 angstrom, and the layers are connected through two crystallographically independent NCN2- units. While one Cu-I is linearly bonded to an NCN2- unit and an additional NH3 molecule, the other Cu-I is also linearly coordinated but by two NCN2- groups; the Cu-N bonds lie between 1.86-1.98 angstrom. The C-N bond lengths and angles evidence both NCN2- groups as essentially linear cyanamides.