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

Abstract

The syntheses, crystal structures, IR and electronic absorption spectroscopy of two cyanide precursors cis-M^II(dppm)₂(CN)₂ (M = Ru, 1; Os, 2) (dppm = bis(diphenylphosphino)methane) and four new cyanide-bridged complexes cis-M^II(dppm)₂(CN)₂(Fe^IIIX₃)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 Fe^III–NC–M^II 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 Os^II. 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 Fe^III ions.