The first Fe(II) complex bearing end-to-end dicyanamide as a double bridging ligand: crystallography study and Hirshfeld surface analysis; completed with a CSD survey

Two new polymeric, one and two-dimensional compounds [Fe(dmbpy) (μ_1,5-dca)₂] (1) and [Fe(4,4′-bpy) (μ_1,5-dca)₂].0.24(4,4′-bpy).0.5(EtOH) (2), in which dmbpy = 5,5′-dimethyl-bipyridine, dca = dicyanamide and 4,4′-bpy = 4,4′-bipyridine, has been synthesized under solvothermal conditions and fully characterized by elemental analysis, FT-IR spectroscopy and X-ray single crystal diffraction. Compound 1, with a rare coordination environment, is the only well-known example in which end-to-end double bridged dca ligands and a bidentate bulky aromatic ligand (dmbpy) are coordinated simultaneously to the iron center. Structural analysis of compound 2 showed it is a novel two-dimensional coordination polymer, constructed from repetition of 4,4′-bpy and dca as a bidentate bridging ligand. Changing the co-ligand to 4,4′-bpy, lead to completely different structure geometry and network, which confirms the substantial effect of co-ligand. Furthermore, Hirshfeld surfaces analyses have been performed to help understand the packing.