Resolution and characterization of helicate dimer and trimer complexes of 1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane with copper(i)

Abstract

Complexation of copper(I) with the binucleating ligand, 1,3-bis(9-methyl-1,10-phenanthrolin-2-yl)propane, mphenpr, result in formation of helical dimers, [Cu₂(mphenpr)₂]²⁺. The resolution of the enantiomeric forms of the dimers has been carried out with Δ-[As(cat)₃]⁻ as resolving agent and X-ray structures for two compounds, P-[Cu₂(mphenpr)₂](Δ-[As(cat)₃])₂ and P-[Cu₂(mphenpr)₂](Δ-[As(cat)₃])₂·4(CH₃CN), are reported. The rate of racemization in poorly-coordinating solvents has been examined by ¹H NMR, and is slow. At saturating concentrations of [[Cu₂(mphenpr)₂]²⁺] in acetonitrile, crystals of the helical trimeric complex [Cu₃(mphenpr)₃](ClO₄)₃ are obtained. The X-ray structure of the trimer is reported. This species has also been resolved. As with the helical dimer, racemization in poorly-coordinating solvents is slow, and circular dichroism and ¹H NMR spectra are reported. The absolute configuration of the resolved complex, P-[Cu₃(mphenpr)₃](Δ-[As(cat)₃])₃, has been determined by X-ray crystallography.