Three different bonding modes of cyano groups in the coordination polymer [Cu(en)2(H(2)O)][Cu(en)(2)Ni(2)Cu(2)(CN)(10)] x 2H(2)O (en is 1,2-diaminoethane).

Partial reduction of the Cu(II) ions in the aqueous system Cu(II)-en-[Ni(CN)(4)](2-) (1/1/1) (en is 1,2-diaminoethane) yields a novel heterobimetallic mixed-valence compound, poly[[aquabis(1,2-diaminoethane)copper(II)] [hexa-mu-cyano-tetracyanobis(1,2-diaminoethane)tricopper(I,II)dinickel(II)] dihydrate], [Cu(C(2)H(8)N(2))(2)(H(2)O)][Ni(2)Cu(3)(CN)(10)(C(2)H(8)N(2))(2)] x 2H(2)O or [Cu(en)(2)(H(2)O)][Cu(en)(2)Ni(2)Cu(2)(CN)(10)] x 2H(2)O. The structure is formed by a negatively charged two-dimensional array of the cyano complex [Cu(en)(2)Ni(2)Cu(2)(CN)(10)](n)(2n-), [Cu(en)(2)(H(2)O)](2+) complex cations and water molecules of crystallization. These last are involved in a complicated hydrogen-bonding system. The cyano groups act as terminal, mu(2)-bridging or mu(3)-bridging ligands.