Efficient Asymmetric Synthesis of Δ‐ and Λ‐Enantiomers of (Bipyridyl)ruthenium Complexes and Crystallographic Analysis of Δ‐Bis(2,2′‐bipyridine)(2,2′‐bipyridine‐4,4′‐dicarboxylato)ruthenium: Diastereoselective Homo‐ and Heterochiral Ion Pairing Revisited

Abstract

Abstract Optically pure ruthenium complexes of the type Δ‐ or Λ‐[Ru(bpy) 2 (L−L)][PF 6 ] 2 [L−L = cmbpy = 4′‐methyl‐2,2′‐bipyridine‐4‐carboxylic acid ( 3a , b ); L−L = dcbpy = 2,2′‐bipyridine‐4,4′‐dicarboxylic acid ( 4a , b )] were prepared and fully characterized. The Ru II carboxylate complexes Δ‐ and Λ‐[Ru(bpy) 2 (dcabpy)] ( 5a , b ) (dcabpy = 2,2′‐bipyridine‐4,4′‐dicarboxylate) were resolved efficiently by chiral column chromatography and isolated in good yields. The Δ‐[Ru(bpy) 2 (dcabpy)] ( 5a ) enantiomer was crystallized and its X‐ray molecular structure determined. The enantiomeric nature and the absolute configuration of the tris(bipyridyl)ruthenium complexes were confirmed by NMR and circular dichroism studies. In addition, ion‐pairing interactions between Δ‐Trisphat (Δ‐ 1 , D 3 symmetry) and each enantiomer of the (monocarboxylic acid)Ru II complex ( 3a and 3b , C 1 symmetry) and the dicarboxylic acid complex ( 4a and 4b , C 2 symmetry) were examined by NMR spectroscopy. (© Wiley‐VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003)