Synthesis and structural characterization of infinite single-stranded coordination polymers of optically active bis(oxazoline) ligands with silver trifluoromethanesulfonate

Abstract

Three novel complexes, [Ag(S,S-1)][CF₃SO₃] (3), [Ag(S,S-2)][CF₃SO₃]·0.5H₂O (4) and [Ag(R,R-2)][CF₃SO₃]·0.5H₂O (5) [1  = 2,2-bis(4′-benzyloxazolin-2′-yl)propane, 2  = 2,2-bis(4′-phenyloxazolin-2′-yl)propane] were obtained from silver trifluoromethanesulfonate and the corresponding bis(oxazoline) ligands. The crystal structures of compounds 3 and 4 were determined by X-ray diffraction. The subtle difference in the substitution at the 4-position of the oxazoline ring in the ligands led to a remarkable change in the structures of complexes 3 and 4. Complex 3 is an infinite single-stranded helical coordination polymer with two-fold symmetry and left-handed helicity, while complexe 4 is an infinite single-stranded polymer with zig-zag conformation. However, the extended structures are not maintained in solution, undergoing rapid ligand redistribution and rapid dynamic exchange among several nonequivalent species as determined by ESMS spectra.