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

Previously,
we synthesized π-conjugated trinuclear metalladithiolene complexes
based on benzenehexathiol (J. Chem. Soc., Dalton Trans. 1998, 2651; 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 92–, substantiating the existence
of electronic communication among the three metal nuclei. These observations
prove that the triphenylene backbone transmits π-conjugation
among the three metalladithiolene units.