Transition metal complexes with sulfur ligands. XXVIII. Ruthenium complexes of the pentadentate thioether thiolate ligands dpttd2− (2,3,11,12-dibenzo-1,4,7,10,13-pentathiatridecane(−2)) and the sterically demanding derivative tbu4-dpttd2− (14,16,18,20-tetra (t-butyl)-2,3,11,12-dibenzo-1,4,7,10,13-pe