Eight new sulfur-rich [CpCo(dithiolene)] complexes were synthesized from [Zn(dmit)(2)](2-) as a starting material. The structures, electrochemical behavior and electronic absorption spectra of the sulfur-rich [CpCo(S(2)C(2)S(2)Y)] complexes could be compared with the early data of analogous Ni complexes. [CpCo (pddt)] (Y= -(CH(2))(3)-), [CpCo(dpdt)] (Y = -CH(2)C(CH(2))CH(2)-), [CpCo(bddt)] (Y = -(CH(2))(4)-), [CpCo(dtdt)] (Y = -CH(2)SCH(2)-) and [CpCo(poddt)] (Y = -CH(2)C(O)CH(2)-) crystallized in all isostructural with the corresponding paramagnetic [CpNi(dithiolene)](center dot) complexes, but [CpCo(dmid)] (Y =C=O), [CpCo(dddt)] (Y= -(CH(2))(2)-) and [CpCo(F(2)pddt)] (Y= -CH(2)CF(2)CH(2)-) crystallized in non-isostructural with them. These molecules are associated with intermolecular short S center dot center dot center dot S contacts in the crystals. [CpCo(F(2)pddt)] did not show any remarkable S center dot center dot center dot S contacts but indicated interesting fluorine segregation and Cp center dot center dot center dot Cp face-to-face interactions. Redox potentials of [CpCo(dithiolene)] complexes were obtained with the cyclic voltammetry measurements and dimerized by electrochemical oxidations. Electronic absorption spectra of [CpCo(dithiolene)] complexes showed visible absorption in the range of 585-701 nm as lowest energy wavelengths (epsilon = 9800-11,800 M(-1) cm(-1)) in solutions, and they were higher energy than those of [CpNi (dithiolene)](center dot) complexes (near-IR). (C) 2010 Elsevier B.V. All rights reserved.