Construction of Pd-based coordination cages with three geometrically distinct ligands

Abstract

Three different dipyridyl ligands were combined with [Pd(CH₃CN)₄](BF₄)₂ to give mixtures of homo- and/or heteroleptic coordination cages. The three ligands were chosen so that one ligand shows a parallel orientation of the coordinate vectors, the second ligand a bent angle of 60°, and the third ligand a bent angle of 120°. We have identified ligand mixtures that give rise to integrative self-sorting, and we have characterized a heterotrileptic [Pd₄L₂L′₂L′′₄]⁸⁺ cage by single crystal X-ray crystallography. The structural flexibility of ligands with alkynyl spacers was found to be of importance for the formation of heteroleptic complexes.