Three diruthenium compounds, [Na(18-crown-6)(thf)2][Ru 2(O2CCH3)2(t-Busalpy)2] (1), [K(18-crown-6)(thf)2][Ru2(O2CCH 3)2(t-Busal-4-Mepy)2] (2), and [K(18-crown-6)(thf)(H2O)][K(18-crown-6)(thf)(MeO)][Ru 2(O2CCH3)2(t-Busal-5-Mepy) 2] (3) (18-crown-6 = 1,4,7,10,13,16-hexaoxocyclooctadecane; 18-crown-6-ether), have been synthesized by the ligand substitution reaction of Ru2(O2CCH3)4Cl with newly prepared tridentate bridging/chelating ligands, N-(2-pyridyl)-2-oxido-3,5-di-tert- butylbenzylaminato (t-Busalpy2-), N-(4-methyl-2-pyridyl)-2-oxido-3,5- di-tert-butylbenzylaminato (t-Busal-4-Mepy2-), and N-(5-methyl-2-pyridyl)-2-oxido-3,5-di-tert-butylbenzylaminato (t-Busal-5-Mepy2-), respectively, and isolated using [Na(18-crown-6)]+ or [K(18-crown-6)]+ as the counter cation. The structural features of the anionic parts are very similar to those of the previously synthesized family of [Ru2(O2CCH 3)2(5-Rsalpy)2]- (R = H, Me, Cl, Br, and NO2); two acetate and two t-Busal-R′py2- ligands are respectively located around the Ru2 unit in a trans fashion, where the t-Busal-R′py2- ligand acts as a tridentate ligand having both bridging and chelating characters to form the M-M bridging/axial-chelating mode. Their Ru-Ru bonded core with an electronic configuration of σ2π4δ2(π *δ*)3 is axial-capped by the di-t-butylphenolate groups of the t-Busal-R′py2- ligands, and experiences multi-redox properties: a one-electron reduction to Ru24+ and two one-electron oxidations to Ru26+ followed by Ru27+, in addition to t-Busal-R′py2- ligand-centered redox. The strong electron-donating ability of the t-butyl groups compared with the other R-groups leads to negative shifts of the redox potentials according to the Hammett law.
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