Sila[1]ruthenocenophanes: Long Sought-After Family Members.

During the last three decades, silicon-bridged [1]ferrocenophanes have been developed into an important class of monomers with the resulting polymers being the subject of hundreds of publications. For unknown reasons, not a single example of a silicon-bridged [1]ruthenocenophane is described in the literature. We set out to address this mystery and could synthesize the first sila[1]ruthenocenophanes. Their molecular structures as well as their heat release in the melt, render them as highly strained sandwich compounds that are polymerizable. Why did it take so long to prepare the first sila[1]ruthenocenophanes? This question is addressed by a detailed analysis of the kinetics of the salt-metathesis approach, which reveals a striking difference between ferrocene and ruthenocene.