Hydrogen bonding in two ionic complexes built from octahedral rhenium(III) chalcocyanohydroxo cluster anions and tris(ethylenediamine)nickel(II) cations, [Ni(en)3]2[Re6S8(CN)4(OH)2]·5.5H2O and [Ni(en)3]2[Re6Se8(CN)4(OH)2]·10H2O

► Octahedral Re chalcocyanohydroxo clusters as building blocks. ► Presence of OH and CN groups enables OH⋯NC intercluster hydrogen bonding. ► Chalcogen in the cluster core influences interactions between cluster anions. ► Thermal behavior drastically depends on crystal structures. Two novel octahedral rhenium(III) chalcocyanohydroxo cluster complexes [Ni(en)3]2[Re6S8(CN)4(OH)2]·5.5H2O (1) and [Ni(en)3]2[Re6Se8(CN)4(OH)2]·10H2O (2) have been prepared by reaction of cluster complexes Cs1.68K2.32[Re6S8(CN)4(OH)2]·2H2O and Cs2.75K1.25[Re6Se8(CN)4(OH)2]·H2O with NiCl2 and en (en=ethylenediamine) in aqueous ammonia solutions. Both compounds were characterized by IR-spectra, elemental analysis, EDS, DTA and single-crystal X-ray analysis. Compound 1 crystallizes in the monoclinic space group C2/c, while compound 2 refers to the triclinic space group P-1. The structures of both compounds consist of discrete ions [Ni(en)3]2+, [Re6Q8(CN)4(OH)2]4− and water molecules of crystallization that are bonded by a network of hydrogen bonds. In the structure of 1 the [Re6S8(CN)4(OH)2]4− anions are bound to each other via OH⋯NC hydrogen interactions (O⋯N distance is 2.950(10)Å), thus forming a linear chains running along the c axis.