Ruthenium(II) Complexes of Multidentate Ligands Derived from Di(2-pyridyl)methane

Abstract

Bis(2,2′-bipyridyl)ruthenium complexes of the model ligand di(2-pyridyl)methane (1) and its multidentate derivatives 1,1,2,2-tetra(2-pyridyl)ethane (2), tetra(2-pyridyl)ethene (3), and hexa(2-pyridyl)[3]radialene (4) have been prepared and characterized by NMR, visible absorption spectroscopy, electrochemical measurements, and, in two cases, by X-ray crystallography. Complexes of (2) and (3) exist as conformationally rigid species with lower than expected symmetry. Ligands (2) and (3) proved surprisingly resistant to forming dinuclear ruthenium complexes. The two diastereoisomeric dinuclear complexes of (4), Δ Λ/Λ Δ and Δ Δ/Λ Λ (rac), are shown to be locked in conformations of C₁ and C₂ point-group symmetry, respectively. This represents a rare example where the Δ Λ/Λ Δ-dinuclear complex of a achiral, symmetrically bridging ligand is not a meso compound.