Sulfur-rich CpCo(dithiolene) complexes: Isostructural or non-isostructural couples of CpCo(III) with CpNi(III) dithiolene complexes

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(S₂C₂S₂Y)] complexes could be compared with the early data of analogous Ni complexes. CpCo(pddt)] (Y = -(CH₂)₃-), CpCo(dpdt)] (Y = -CH₂C(CH₂)CH₂-), CpCo(bddt)] (Y = -(CH₂)₄-), CpCo(dtdt)] (Y = -CH₂SCH₂-) and CpCo(poddt)] (Y = -CH₂C(O)CH₂-) crystallized in all isostructural with the corresponding paramagnetic CpNi(dithiolene)] complexes, but CpCo(dmid)] (Y = CO), CpCo(dddt)] (Y = -(CH₂)₂-) and CpCo(F₂pddt)] (Y = -CH₂CF₂CH₂-) crystallized in non-isostructural with them. These molecules are associated with intermolecular short S?S contacts in the crystals. CpCo(F₂pddt)] did not show any remarkable S?S contacts but indicated interesting fluorine segregation and Cp?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 (? = 9800-11,800 M⁻¹ cm⁻¹) in solutions, and they were higher energy than those of CpNi(dithiolene)] complexes (near-IR).