Migration of 1,3-diazacyclohexane sub-rings in ring-contracted macrocyclic silver(I) complexes

Mononuclear and dinuclear silver(I) complexes with contracted macrocyclic ligands were synthesized ([AgLd]BPh4, 1, and [Ag2Lb](BPh4)2 · 2(DMF), 2). X-ray structural analysis revealed that in 1 the coordinated ligand Ld adopted a ring-contracted cis-form, with two 1,3-diazacyclohexane sub-rings positioned in a cis-configuration with respect to the macrocyclic ring center, while in 2 the ligand Lb adopted a ring-contracted trans-form. 1H NMR and X-ray structural analysis revealed that the cis- and trans-forms are interconvertible depending on whether the complex is mononuclear or dinuclear and whether it is in crystalline form or in solution; i.e., the 1,3-diazacyclohexane sub-ring is capable of migration in ring-contracted macrocyclic silver(I) complexes.