Rational Synthesis and Complexation Behavior of the Bidentate Lewis Acid 1,2-Bis(chloromercury)ferrocene

1,2-Disubstituted ferrocenes represent an interesting, yet underdeveloped class of redox-active bidentate Lewis acids. We describe here a new rational synthesis of 1,2-bis(trimethylstannyl)ferrocene (2) and its high yield conversion to 1,2-bis(chloromercury)ferrocene (3). X-ray crystal structures for complexes of the bidentate Lewis acid 3 with DMSO,
[Bu4N]Cl, and [PPh4]Cl were obtained. In all cases the two Hg atoms form reverse chelates
with the nucleophile. With DMSO a 1:1 complex is formed, in which DMSO is coordinated
from the endo side of ferrocene. Two molecules of 3 are used in the binding to the chloride
anion. Different modes are realized with the two different counterions. In the complex with
[Bu4N]Cl the chloride ion is coordinated from the exo side of both ferrocenes, while with
[PPh4]Cl the chloride ion is endo with respect to one and exo with respect to the other
ferrocene moiety. Layered and channel-like supramolecular structures are realized with
[Bu4N] and [Ph4P] counterions, respectively.