Dynamic ring-opening polymerization of silver(i) complexes with bis(amidopyridine) ligands

Abstract

The factors which influence the formation of chelate, macrocycle or polymer in the reaction of silver(I) salts with bis(pyridine) ligands have been probed by studying structures in the solid state and cold spray ionization mass spectra in solution, with the ligands C₆H₄-1,3-[CONR(CH₂)_n-3-C₅H₄N]₂, 1 (R = Me, n = 0) or 3 (R = H, n = 1) or 5-t-Bu-C₆H₃-1,3-[CONR(CH₂)_n-4-C₅H₄N]₂, 2 (R = Me, n = 0) or 4 (R = H, n = 1). In both the solid state and solution, the complex [Ag(1)₂]BF₄ exists as a chelate complex 5. The ligands NN = 2–4 form complexes in the solid state with either macrocyclic structures [Ag₂(μ-NN)₂]X₂ [6, NN = 2, X = BF₄; 9, NN = 3, X = NO₃] or polymeric structures [7, NN = 2, X = NO₃; 8, NN = 3, X = CF₃CO₂; 10, NN = 4, X = CF₃CO₂]. The ligands 2 and 3 gave both macrocyclic and polymeric complexes, depending on the anion. In solution, these complexes existed as mixtures of macrocycles and ring-opened oligomers. In the crystalline state, the complexes 6–10 underwent supramolecular association through combinations of hydrogen bonding, secondary bonding of the type Ag⋯X to anions, or argentophilic bonding of the type Ag⋯Ag.