An unusually weak intervalence transition in a very stable bis chelate analog of the ruthenium mixed-valent Creutz-Taube ion. UV/visible/near-IR and EPR spectroelectrochemistry of (NH3)4Ru(m-bptz)Ru(NH3)4n+ (bptz = 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine; n = 3 - 5). Inorganic Chemistry, (32)12:2640--2643, 1993. [PUMA: ESR ammine complex complex;UV complex;redox complex;ruthenium electronic factor g potential pyridyl ruthenium spectrum structure tetrazine]