Dynamic properties of a diruthenium complex with ligand-unsupported Ru–Ru triple bonds, Na 2 [Ru 2 (3,6-DTBCat) 4 ] (1), were studied using variable-temperature 1 H NMR. Structural freedom derived from the ligand-unsupported structure leads to torsional motion about the Ru–Ru bonds in THF and in DMF. The observed solvent dependency corresponds to the electrostatic interactions between the diruthenium complex and Na + counter cations, which are sensitive to the polarity of solvents. In addition, a new diruthenium complex, [{Na(THF) 2 (H 2 O)}{Na(THF) 0.5 (H 2 O)}{Ru 2 (3,6-DTBCat) 2 (H 4 Cat) 2 }] (2·2.5THF·2H 2 O), with a ligand-unsupported Ru–Ru bond surrounded by two different kinds of catecholate derivatives, has been synthesized and crystallographically characterized. The complex, which was characterized by single-crystal structural analysis, will provide an opportunity to investigate not only static molecular structures but also dynamic physicochemical properties in comparison with analogues containing four identical catecholate derivatives.