Use of the Electron-Reservoir [FeICp(arene)] Sandwiches as Efficient and Selective Electrocatalysts: Syntheses of Homo- and Heterodinuclear Zwitterionic Transition-Metal Fulvalene Complexes

The electron-reservoir complexes [FeICp(C6H6)], [FeICp(C6Me6)], and [FeICp*(C6Me6)] (Cp = η5-C5H5; Cp* = η5-C5Me5) have been used as initiators in THF for the electron-transfer-chain-catalyzed (electrocatalyzed) synthesis of the homobimetallic zwitterions [(CO)3M-FvM+(CO)2(PR3)2] (M = Mo, W; Fv = μ2-η10-fulvalene; R = Me, OMe) from [M2Fv(CO)6] and PR3 and of the heterobimetallic zwitterions [(CO)3MIFvM2(CO)(PR3)2] (M1 = Mo, W; M2 = Fe, Ru) from [M1M2Fv(CO)5] and PR3. Cyclic voltammetry (CV) experiments (DMF, 0.1 M n-Bu4NBF4, Pt, 0.400 V s-1) show that the CV's of the homobimetallic starting materials are unchanged in the presence of PR3 (R = Me, OMe) whereas those of the heterobimetallic complexes in the presence of PMe3 show only the CV's of the zwitterions. This indicates that the electrocatalytic process of the homobimetallic complexes is slow on the electrochemical time scale whereas that of the heterobimetallic complexes with PMe3 is fast on the same time scale. This dichotomy is taken into account i...