Donor-substituted CpCo-stabilized cyclobutadienes and superphanes

RCpCoL2 complexes (L2 = (CO)2 or COD, R = H, CO2Me, TMS) were reacted with various alkynes substituted with chalcogen atoms adjacent to the triple bonds. These reactions yielded hetero-substituted CpCo-capped cyclobutadienes and superphanes dependent on the ring size of the corresponding cyclic diene used as starting material. Reactions in decaline afforded not only CpCo-capped cyclobutadieno superphanes, but also mixed cyclobutadieno cyclopentadienono superphanes. X-ray analyses do not indicate a significant amount of conjugation between the π systems and the lone pairs of the heteroatoms whereas cyclic voltammetry reveals an easier oxidation when increasing the number of electron-donating heteroatoms.