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3.Organometallic catalysis, resolution of metal complexes via chiral anion recognition.

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Resolution of a rare binuclear ruthenium compounds via chiral anion recognition
The binuclear ruthenium trans-[bis(Cp*Ru)-carbazolyl][PF6], has a C2 symmetry and belongs to compounds with planar chirality (Figure 1).

         
                       a)                                                                b)

Figure. a) Binuclear ruthenium complex trans-[bis(Cp*Ru)-carbazolyl][PF6] ; b) Structure of trans-[(Sp,Sp)-bis(Cp*Ru)-carbazolyl][Δ-Trisphat] showing chiral anion recognition. Organometallics 2004, 23, 4338.

The PF6- anion of the racemic dinuclear ruthenium compound can be replaced by Δ-Trisphat through anion metathesis to give two pair of diastereomers. These diastereomers [trans-[(Sp,Sp)-bis(Cp*Ru)-carbazolyl][Δ-Trisphat] and trans-[(Rp,Rp)-bis(Cp*Ru)-carbazolyl][Δ-Trisphat] can be separated by fractional crystallization. X-ray molecular structure of the trans-[(Sp,Sp)-bis(Cp*Ru)-carbazolyl][Δ-Trisphat] was ascertained by single crystal X-ray diffraction study. The complex crystallizes in the chiral space group P21. The absolute configuration was determined by using the Flack’s parameter (x = 0.07). The CD curve of the crystal was recorded and confirmed the configuration obtained from the X-ray study.

Our future objectives is devoted to the use of such chiral complexes as ligands to promote enantioselective catalytic C-C bond formation.