A series of new dicobalt complexes of the permethylated macrocyclic hexaamine dithiophenolate ligand H₂L^Me have been prepared and investigated in the context of ligand binding and oxidation state changes. The octadentate ligand is an effective dinucleating ligand that supports the formation of bioctahedral complexes with a central N₃Co(μ-SR)₂(μ-X)CoN₃ core structure, leaving a free bridging position X for the coordination of the substrates. The acetato- and cinnamato-bridged complexes [(L^Me)Co^II₂(μ-O₂CMe)]⁺ (2) and [(L^Me)Co^II₂(μ-O₂CCHCHPh)]⁺ (5) were prepared by reaction of the μ-Cl complex [(L^Me)Co^II₂(μ-Cl)]⁺ (1) with the corresponding sodium carboxylates in methanol. The electrochemical properties of these and of the methyl carbonate complex [(L^Me)Co^II₂(μ-O₂COMe)]⁺ (8) were also investigated. All complexes undergo two stepwise oxidations at ca. E¹_1/2 = +0.22 and at E²_1/2 = ca. +0.60 V vs SCE, affording the mixed-valent complexes [(L^Me)Co^IICo^III(μ-O₂CR)]²⁺ (3, 6, 9) and the fully oxidized Co^IIICo^III forms [(L^Me)Co^III₂(μ-O₂CR)]³⁺ (4, 7, 10), respectively. Compounds 3, 6, 9 and 4, 7, 10 refer to acetato-, cinnamato-, and methylcarbonato species, respectively. The Co^IICo^III compounds were prepared by comproportionation of the respective Co^II₂ and Co^III₂ compounds. The Co^IIICo^III species were prepared by bromine oxidation of the Co^IICo^II forms. The crystal structures of complexes 2·BPh₄·MeCN, 3·(I₃)₂, 5·BPh₄·2MeCN, 6·(ClO₄)₂·EtOH, 7·(ClO₄)₃·MeCN·(H₂O)₃, and 9·(ClO₄)₂·(MeOH)₂·H₂O were determined by single-crystal X-ray crystallography at 210 K. The oxidations occur without gross structural changes of the parent complexes. The Co^IICo^III complexes are composed of high-spin Co^II (d⁷) and low-spin Co^III (d⁶) ions. The Co^IIICo^III complexes are diamagnetic. The oxidation reactions affect the binding mode of the substrates. In the Co^II₂ and Co^IICo^III forms the carboxylates bridge the two Co²⁺ ions in a symmetric μ-1,3 fashion with uniform C−O bond distances, whereas asymmetric bridging modes, with one short CO and one long C−O distance, are adopted in the fully oxidized species. This is consistent with the observed shifts in vibrational frequencies for ν_as(C−O) and ν_s(C−O) across the series.