π-Conjugated Trinuclear Group-9 Metalladithiolenes with a Triphenylene Backbone

Previously, we synthesized pi-conjugated trinuclear metalladithiolene complexes based on benzenehexathiol (j. Chem. Soc., Dalton Trans. 1998, 2641; Dalton Trans. 2009, 1939; Inorg. Chem. 2011, 50, 6856). Here we report trinuclear complexes with a triphenylene backbone. A reaction with triphenylenehexathiol and group 9 metal precursors in the presence of triethylamine gives rise to trinuclear complexes 9-11. The planar structure of 11 is determined using single crystal X-ray diffraction analysis. The ligand-to-metal charge transfer bands of 9-11 move to longer wavelengths compared with those of mononuclear 12-14. Electrochemical measurements disclose that the one-electron and two-electron reduced mixed-valent states are stabilized thermodynamically. Uv-vis-NIR spectroscopy for the reduced species of 9 identifies intervalence charge transfer bands for 9(-) and 9(2-), substantiating the existence of electronic communication among the three metal nuclei. These observations prove that the triphenylene backbone transmits pi-conjugation among the three metalladithiolene units.