Intramolecular “CH···π(Metal Chelate Ring) Interactions” as Structural Evidence for Metalloaromaticity in Bis(pyridine‐2,6‐diimine)Ru^II Complexes

Abstract

Abstract The synthesis and structural characterization of two novel Ru II complexes ( 1 and 2) with tridentate pyridine‐2,6‐diimine ligands are described. In both compounds, ortho ‐CH bonds from the phenyl or phenyl‐like rings produce unexpected CH ··· π interactions with ruthenium‐α,α'‐diimine chelate rings. This insight is thought to provide new structural evidence for the metalloaromaticity of the chelate rings in the ruthenium complexes studied. The molecular geometry of complex 1 is remarkably similar to S 4 symmetrical geometry, which is also a consequence of the four CH ··· π(chelate ring) interactions working cooperatively. In contrast, there are only two pairs of these interactions working in complex 2 because of the steric effects and electronic influences caused by the methyl‐group substitutions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)