Tuning the link of doubly silyl-bridged ferrocenes

New 4,4,8,8-tetraalkyltetrahydro-4,8-disila-s-indacene ligands were synthesized in order to increase the solubility of higher-nuclear bridged metallocenes. CpNa and R2SiCl2 (R = Et, n-Bu) gave the silylated cyclopentadienes (C5H5)SiR2Cl that were converted to disila-s-indacenes carrying R at the silyl bridges. Deprotonation led to the corresponding dianions, which after addition of CpNa, reacted with solvated iron dichloride to yield dinuclear ferrocenes that were bridged by R2Si groups. In any case, mixtures of syn- and anti-isomers were obtained from which the pure anti-isomers could be separated by crystallization. All compounds were characterized by H-1- and C-13-NMR spectroscopies and partly by mass spectroscopy. In cyclic voltammetry, the anti-isomers of the dinuclear ferrocenes underwent successive electron transfers with separations that were determined by solvation effects. (C) 1999 Elsevier Science S.A. All rights reserved.