Orientational Self-Sorting in Octahedral Coordination Cages Based on Small, Heteroditopic N-Donor Ligands

Abstract

Coordination cages based on heteroditopic N-donor ligands can potentially form isomers, which differ in the relative orientation of the ligands. We have explored the construction of octahedral cages using small low-symmetry N-donor ligands (L). When the ligands were combined with [Pd(CH3CN)4](BF4)2, hexanuclear Pd6L12-type cages were obtained as a mixture of isomers, as evidenced by NMR spectroscopy and single-crystal X-ray crystallography. Attempts to resolve the isomers by cyclic ion mobility-mass spectrometry (cIM-MS) are described. Structurally defined cages of the general formula [Pt2Pd4Cl8L8](BF4)4 were formed in kinetically controlled reactions of homoleptic [PtL4](BF4)2 complexes with PdCl2(CH3CN)2. Crystallographic analyses of the products have revealed antipodal Pt2+ centers, the pyridine or pyrimidine donor groups of the bridging ligands being exclusively bound to the four equatorial PdCl2 complexes.