Synthesis and Electrochemical Behavior of Ferrocenyl ‐ Functionalized Metallocenes M(η 5 ‐ C 5 H 5 ) 2 (EFc) 2 (M = Ti, Zr; E = O, S, Se)

Metallocenes [Ti](Cl)(OFc) ( 4 ) and [M](EFc) 2 {[M] = M(η 5 ‐ C 5 H 5 ) 2 ; M = Ti: 5a , E = O; 5b , E = S; 5c , E = Se. M = Zr: 6 , E = O; Fc = Fe(η 5 ‐ C 5 H 4 )(η 5 ‐ C 5 H 5 )} were prepared by the treatment of [M]Cl 2 ( 1 , M = Ti; 2 , M = Zr) with FcOLi ( 3 ), or by the reaction of FcELi ( 8a , E = S; 8b , E = Se) with 1 . The solid‐state structures of the metallocenes 4 , 5a , b , and 6 are reported. The electrochemical ( 4 , 5a , b , c ) and spectroelectrochemical (in situ UV/Vis/NIR) [ 5a , Fc 2 E 2 for comparison; E = S ( 9 ), Se ( 10 )] behavior is discussed. All Ti compounds show irreversible Ti IV /Ti III reduction processes at E pc = –1520 to –2100 mV. Reversible Fc redox processes are characteristic for 4 ( E 1 °′ = –308 mV) and 5a ( E 1 °′ = –429, E 2 °′ = –142 mV). For 5b three processes at E 1 °′ = –151, E 2 °′ = 87, and E 3 °′ = 369 mV are found. In multicyclic CV studies it could be shown that after Ti IV /Ti III reduction the Ti–S bonds in 5b were cleaved resulting in the formation of Fc 2 S 2 ( 9 ), which shows two separate reversible redox processes at E 1 °′ = 64 and E 2 °′ = 366 mV for the Fc groups. However, metallocene 5c decomposes in solution producing 10 . UV/Vis/NIR studies on 5a , 9 , and 10 indicate significant electrostatic interaction among the Fc/Fc + groups as oxidation progresses.