Synthesis, crystal structure and MMCT of new cyanide-bridged complexes cis-MII(dppm)2(CN)2(FeIIIX3)2 (M = Ru, Os)

The syntheses, crystal structures, IR and electronic absorption spectroscopy of two cyanide precursors cis-MII(dppm)2(CN)2 (M = Ru, 1; Os, 2) (dppm = bis(diphenylphosphino)methane) and four new cyanide-bridged complexes cis-MII(dppm)2(CN)2(FeIIIX3)2 (M = Ru, X = Cl, 3; M = Ru, X = Br, 4; M = Os, X = Cl, 5; M = Os, X = Br, 6) are reported. The crystal structural data, IR and the MMCT (metal-to-metal charge transfer) in the electronic absorption spectroscopy indicate the existence of some electron delocalization along FeIII–NC–MII arrays in complexes 3–6. The presence of a newer MMCT band of the Os-based complexes (5 and 6) than the Ru-based complexes (3 and 4) should result from the larger spin–orbit coupling (SOC) of OsII. Also the theoretical calculated values of the crystal structural data and IR spectra are consistent with the experimental values. Temperature-dependent magnetic properties of complexes 3–6 reveal the presence of the very weak metal–metal interaction between distant FeIII ions.