Synthesis and characterization of binuclear transition metal-rhenium(VII) complexes with bridging cyanide ligands

Reacting transition metal complexes in low oxidation states, containing one or two cyanide ligands, with methyltrioxorhenium(VII) leads to bridged mixed metal compounds in good yields. The Re(VII) core is then surrounded by five or six ligands, respectively. The strength of these CN bridges and thus the stability of the newly generated bimetallic compound strongly depends on the donor strength of the ligands surrounding of the Cr/Mo/W or Fe moiety. The stability of the mixed metal molecules is reflected in the temperature dependent behavior of their ¹⁷O-NMR spectra, in their IR (Re=O) stretching frequencies and force constants, as well as several other spectroscopic data. UV-vis absorption spectra show the appearance of charge transfer bands. In the case of the mixed Mo/Re complexes the ⁹⁵Mo-NMR spectroscopy is also a helpful tool to examine the donor capability of the Mo moiety. The described compounds also show photosensitivity.