Synthesis and Electrochemical Behavior of Ferrocenyl-Functionalized Metallocenes M((5)-C5H5)(2)(EFc)(2) (M = Ti, Zr; E = O, S, Se)

Metallocenes [Ti](Cl)(OFc) (4) and [M](EFc)(2) {[M] = M((5)-C5H5)(2); M = Ti: 5a, E = O; 5b, E = S; 5c, E = Se. M = Zr: 6, E = O; Fc = Fe((5)-C5H4)((5)-C5H5)} 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 degrees = -308 mV) and 5a (E-1 degrees = -429, E-2 degrees = -142 mV). For 5b three processes at E-1 degrees = -151, E-2 degrees = 87, and E-3 degrees = 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 degrees = 64 and E-2 degrees = 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.