Structure and stability of neutral cyanide complexes of copper and zinc

A theoretical study of neutral Zn[CN]n and Cu[CN]n complexes has been carried out, as representative examples of cyanide complexes of late transition metals. Both complexes prefer the cyanide arrangement over the isocyanide form, in agreement with the experimental evidence for the monocyanide compounds. The successive complexation energies suggest that the preferred complex in the case of copper is the monocyanide, CuCN, whereas for zinc the most favourable complex seems to be Zn(CN)2. Both Zn and Cu have preference for low coordination numbers, since mixed complexes with cyanide and cyanogen ligands are preferred over homoleptic M(CN)n complexes for n > 2.