Chiral recognition and resolution mediated by pi-pi interactions: Synthesis and X-ray structure of trans-[(Sp,Sp)-bis(Cp*Ru)-carbazolyl][Delta-trisphat]

摘要

A planar chiral dinuclear ruthenium complex has been prepared and obtained as a pair of diastereomers, trans-[(Sp,Sp)-bis(Cp*Ru)-carbazolyl][Delta-Trisphat] (4a) and trans-[(Rp,Rp)-bis(Cp*Ru)-carbazolyl][Delta-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 Delta-Trisphat anion pi-stacks (d(average) = 3.62(1) Angstrom, alpha(average) = 20.16degrees) with a single enantiomer of the C-2-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 Delta-Trisphat salt is possible, important results for uses as chiral organometallic reagents and catalysts.