Two isostructural square grid networks were formed by reacting a Langmuir monolayer of an amphiphilic pentacyanoferrate (3+) complex with aqueous Co2+ or Mn2+ ions dissolved in the subphase. Confinement of the reactants to the air–water interface discriminates against the formation of higher dimensional products and directs the lateral propagation of a polymeric two-dimensional cyanide-bridged network. The network can be transferred to a variety of supports to form monolayer or multilayer lamellar films by the Langmuir–Blodgett (LB) technique. Characterization of both the Fe–Co and Fe–Mn LB film extended networks by FTIR spectroscopy, SQUID magnetometry, and grazing incidence synchrotron X-ray diffraction (GIXD) reveals face-centered square grid structures directed by the defined bond angles of the octahedral metal complexes and the linear cyanide bridges. Magnetic measurements on both samples indicate the presence of anisotropic low temperature magnetic exchange interactions between the paramagnetic centers. The results illustrate the potential utility of an interface as a structure director in the assembly of low dimensional coordinate covalent network solids.