Abstract: | The reaction of N1,N1′‐(ethane‐1,2‐diyl)bis(propane‐1,3‐diamine) (bapen), K2Ni(CN)4]·H2O and dimethylformamide in the presence of Gd(NO3)3·6H2O under solvothermal conditions yielded yellow crystals of dicyanido(2,3,4,6,7,9,10,11‐octahydropyrimido2′,1′:3,4]pyrazino1,2‐a]pyrimidine)nickel(II) hemihydrate, Ni(CN)2(C10H16N4)]·0.5H2O, (I), the crystal structure of which is composed of Ni(CN)2(pdpm)] molecules (pdpm is 2,3,4,6,7,9,10,11‐octahydropyrimido2′,1′:3,4]pyrazino1,2‐a]pyrimidine) on general positions linked by O—H...N hydrogen bonds to water molecules located on twofold axes. This structural unit is further linked by nonclassical C—H...N interactions to form a warped two‐dimensional net perpendicular to the unit‐cell b axis. The nets are stacked, with C—H...O contacts joining successive units. The NiII cation is coordinated with square‐planar geometry by a chelating pdpm ligand and two cyanide ligands in mutually cis positions. Complex (I) is stable up to 360 K, at which point dehydration takes place; the ligands start to decompose at 558 K. |