Reaction between [Ni(cyclam)]²⁺ and [W(CN)₈]⁴⁻ leads to the formation of a 3D diamond-like network [Ni(cyclam)]₂[W(CN)₈]·3.5H₂O (1). The structure is characterised by a network of intersecting channels of 3–4 Å in diameter, filled with crystallisation water, most of which is released upon drying in air, causing the crystals to collapse. Analogous compound [Ni(cyclam)]₂[Nb(CN)₈]·3.5H₂O (2), based on paramagnetic Nb(IV), could only be obtained as a powder, due to the decomposition of the [Nb(CN)₈]⁴⁻ complex under slow diffusion conditions. It shows long-range magnetic ordering with T_C = 11.8 K and magnetic hysteresis at 2 K. These properties are lost upon drying in air. After rehydration differently shaped hysteresis appears, which together with AC susceptibility measurements suggests the formation of a multiphase system. Subsequent dehydration–rehydration experiments show partial reversibility.