Synthesis and structure determination of Co(HNCN)2 and Ni(HNCN)2

Well-crystallized cobalt and nickel hydrogencyanamide, Co(HNCN)2 and Ni(HNCN)2, were synthesized from the corresponding ammonia complexes [M(NH3)6]2+ under aqueous cyanamide conditions. The X-ray and neutron powder data evidence the orthorhombic system and space group Pnnm. The cell parameters for Co(HNCN)2 are a=6.572(1), b=8.805(2), c=3.267(1) Å, and Z=2; for the isotypic Ni(HNCN)2, the cell parameters arrive at a=6.457(1), b=8.768(2), c=3.230(1) Å. The octahedral coordinations of the metal ions are marginally squeezed, with interatomic distances of 4×Co–N=2.134(5) Å, 2×Co–N=2.122(9) Å, and 4×Ni–N=2.133(6) Å, 2×Ni–N=2.035(11) Å. The HNCN− units appear as slightly bent (177.5(2)° for Co(HNCN)2 and 175.7(2)° for Ni(HNCN)2) and exhibit cyanamide shape character due to triple- and single-bond C–N distances (1.20(2) vs. 1.33(2) Å for Co(HNCN)2 and 1.15(2) vs. 1.38(2) Å for Ni(HNCN)2). The infrared vibration data compare well with those of the three existing alkali-metal hydrogencyanamides.