Structural sources of chiral discrimination in diastereoisomeric Ru(II) complexes of aromatic aminoacids and diimines

The single-crystal structure of a previously reported Ru(II) complex salt, Δ-[Ru(bpy)2(S-tyr)]ClO4 · benzene (bpy = 2,2′-bipyridyl; tyr = tyrosinato) has been refined in its correct setting. The salt contains the cation that is thermodynamically unstable in aqueous solution at 298 K with respect to the Λ diastereoisomer. Its stability in the solid state is ascribed to the influence of intramolecular NH–π and CH–π interactions involving the aromatic ring of the aminoacidate with the amine group and a pyridyl ring of one of the diimine ligands. The benzene of crystallization is involved with similar CH–π, π–π and π-facial interactions with the bpy and tyrosinato ligands, and this too may serve to stabilize the particular diastereoisomer in the lattice.