Stereoselectivity in the formation of tris-diimine complexes of Fe(ii), Ru(ii), and Os(ii) with a C2-symmetric chiral derivative of 2,2′-bipyridine

Abstract

A C₂-symmetric enantiopure 4,5-bis(pinene)-2,2′-bipyridine ligand (−)-L was used to investigate the diastereoselectivity in the formation of [ML₃]²⁺ coordination species (M = Fe(II), Ru(II), Os(II), Zn(II), Cd(II), Cu(II), Ni(II)), and [ML₂Cl₂] (M = Ru(II), Os(II)). The X-ray structures of the [ML₃]²⁺ complexes were determined for Δ-[FeL₃](PF₆)₂, Δ-[RuL₃](PF₆)₂, Λ-[RuL₃](PF₆)₂, Δ-[OsL₃](PF₆)₂, and Λ-[OsL₃](TfO)₂. All of these compounds were also characterized by NMR, CD and UV/VIS absorption spectroscopy. The [FeL₃]²⁺ diastereoisomers were studied in equilibrated solutions at various temperatures and in several solvents. The [RuL₃]²⁺ complexes, which are thermally stable up to 200 °C, were photochemically equilibrated.