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What a Difference Ancillary Thienyl Makes: Unexpected Additional Stabilization of the Diruthenium(III,II) but Not the Diosmium(III,II) Mixed-Valent State in Tetrazine Ligand-Bridged Complexes

, , , , , , and . Inorganic Chemistry, 42 (20): 6172--6174 (2003)
DOI: 10.1021/ic034105p

Abstract

The Ru2III,II mixed-valent state is strongly stabilized in (bpy)2Ru(m-bttz)Ru(bpy)25+ (35+), bttz = 3,6-bis(2-thienyl)-1,2,4,5-tetrazine, as evident from lowered oxidn. potentials and isolability, a strongly increased comproportionation const. Kc = 1016.6, and a high-energy intervalence charge transfer band at 10100 cm-1. Curiously, no such effects were obsd. for the diosmium(III,II) analog, whereas the related systems (bpy)2M(m-bmptz)M(bpy)25+, bmptz = 3,6-bis(4-methyl-2-pyridyl)-1,2,4,5-tetrazine, exhibit conventional behavior, i.e., a slightly higher Kc value of the Os2III,II analog. EPR signals were obsd. at 4 K for 35+ but not for the other mixed-valent species, and high-frequency (285 GHz). EPR was employed to study the diruthenium(II) radical complexes 23+ and 33+. on SciFinder(R)

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