Synthesis and characterization of bis(ferrocenylcarboxylato)telluranes

A convenient route to the synthesis of the first bis(ferrocenyl carboxylato) telluranes has been developed. Reactions of 1,1,2,3,4,5,6-heptahydro-1,1-(dihydroxo)telturane and 1,1,2,3,4,5-hexahydro-1,1-(dihydroxo)tellurophene with ferrocene carboxylic acid give 1,1,2,3,4,5,6-heptahydro-1,1-bis(ferrocenyl carboxylato)tellurane (3) and 1,1,2,3,4,5,hexahydro-1,1-bis(ferrocenyl carboxylato)tellurophene (5), respectively. The X-ray structure of 3 shows that it contains a tellurium heterocycle (C5H10Te), present in a chair conformation, sandwiched between two ferrocene units with carboxylate groups acting as spacers. Compound 3 also exhibits modest second harmonic generation (SHG) efficiency. The electrochemical studies of 3 and 5 through cyclic voltammetry show only one oxidation wave, indicating the presence of independent redox centers leading to reversible single-step two-electron redox systems.