Syntheses, crystal structures and magnetic properties of two cyanide-bridged molecular squares MII2–CoII2 (M = Ru, Os) based on the diamagnetic cyanidometal M(dppm)2(CN)2

Two tetra-nuclear cyanide-bridged molecular square complexes [MII(dppm)2(CN)2(CoIICl2)]2 (M = Ru, 1; M = Os, 2) (dppm = bis(diphenylphosphino) methane) were synthesized and characterized by elemental analysis, IR, electronic absorption spectra and single-crystal X-ray diffraction analysis. Both the isostructure complexes 1 and 2 crystallize in monoclinic space group P21/c, and possess two cis-M(dppm)2(CN)2 (M = Ru, 1; M = Os, 2) and two CoCl2 units through cyanido bridges. What’s more, the environment around the Co(II) atoms in 1 and 2 define a slightly distorted tetrahedron, and are coordinated by two nitrogen atoms from the cyanide groups with cis-configuration and by two chlorine atoms. Temperature dependence of magnetic susceptibilities show both 1 and 2 are weak antiferromagnetic coupling between the paramagnetic Co(II) ions across a diamagnetic cyanidometal –NC–M(II)–CN– bridge. Furthermore, complex 1 exhibits spin-canted behavior. However, there is no such magnetic behavior in complex 2, which may result from the more diffuse nature of the 5d orbits with respect to 4d.