Chiral Recognition and Resolution Mediated by π−π Interactions: Synthesis and X-ray Structure of <i>trans</i>-[(<i>S</i>p,<i>S</i>p)-bis(Cp*Ru)-carbazolyl][Δ-Trisphat]^†

A planar chiral dinuclear ruthenium complex has been prepared and obtained as a pair of diastereomers, trans-[(Sp,Sp)-bis(Cp*Ru)-carbazolyl][Δ-Trisphat] (4a) and trans-[(Rp,Rp)-bis(Cp*Ru)-carbazolyl][Δ-Trisphat] (4b), through fractional crystallization. The X-ray molecular structure of 4a is reported and shows the formation of a one-dimensional supramolecular species in which the Δ-Trisphat anion π-stacks (daverage = 3.62(1) Å, αaverage = 20.16°) with a single enantiomer of the C2-planar cation [trans-(Sp,Sp)-bis(Cp*Ru)-carbazolyl], suggesting that chiral recognition and resolution occur under supramolecular control. NMR and circular dichroism studies in solution support the solid-state behavior and show that resolution of chiral planar complexes by the Δ-Trisphat salt is possible, important results for uses as chiral organometallic reagents and catalysts.