Cyclic versus Polymeric Supramolecular Architectures in Metal Complexes of Dinucleating Ligands: Silver(I) Trifluoromethanesulfonate Complexes of the Isomers of Bis(di(1H-pyrazolyl)methyl)-1,1′-biphenyl.

Abstract

In the search for new examples of systems that self-assemble into cyclic metal–organic architectures, the six isomers of X, Y ′-bis(di(1 H -pyrazolyl)methane)-1,1′-biphenyl, L XY, and their silver(I) trifluoromethanesulfonate complexes were prepared. Five of the six silver complexes gave crystals suitable for single crystal X-ray diffraction, with only the microcrystalline derivative of 2,3′-bis(di(1 H -pyrazolyl)methane)-1,1′-biphenyl, L 23, proving to be unsuitable for this analysis. Of the structurally characterized silver(I) complexes, that with L 22 showed an unusual trans-spanning chelating coordination mode to silver. At the same time the ligand was also bound to a second silver center giving rise to a cyclic supramolecular isomer with a 22-membered metallacycle. The complex of L 34 also gave a cyclic dication but with a remarkable 28-membered metallacycle ring. The remaining three derivatives were polymeric. The results of this study underscore that a 120° angle between dipyrazolylmethyl moieties across aromatic spacers will give rise to a cyclic dication but this is not an exclusive requirement for the formation of cyclic architectures. Also, the supramolecular structures of complexes are assembled via a variety of noncovalent interactions involving the di(pyrazolyl)methyl cation most notably by weak hydrogen bonding interactions involving the methine hydrogen and an oxygen atom of the triflate anion.