Responsive Four-Coordinate Iron(Ii) Nodes In Fepd(Cn)(4)

Metal node design is crucial for obtaining structurally diverse coordination polymers (CPs) and metal-organic frameworks with desirable properties; however, Fe(II)ions are exclusively six-coordinated. Herein, we present a cyanide-bridged three-dimensional (3D) CP, FePd(CN)(4), bearing four-coordinate Fe(II)ions, which is synthesized by thermal treatment of a two-dimensional (2D) six-coordinate (FeCP)-C-II, Fe(H2O)(2)Pd(CN)(4).4 H2O, to remove water molecules. Atomic-resolution transmission electron microscopy and powder X-ray and neutron diffraction measurements revealed that the FePd(CN)(4)structure is composed of a two-fold interpenetrated PtS topology network, where the Fe(II)center demonstrates an intermediate geometry between tetrahedral and square-planar coordination. This four-coordinate Fe(II)center with the distorted geometry can act as a thermo-responsive flexible node in the PtS network.