Endocyclic and Endo-Exocyclic Silver(I) Complexes of Thiaoxaaza Macrocycles: Crystallographic and NMR Studies

Abstract

A comparative investigation of the coordination behaviour of a 19-memberedNO(2)S(2)-macrocycle (L-1) and a 20-membered NO2S3-macrocycle (L-2) is reported. On silver(I) complexation, L-1 yields a discrete endocyclic mononuclear complex, whereas L-2 affords a one-dimensional coordination polymer in which the endo-coordinated macrocyclic complex units are linked by silver(I) ions outside the cavity via endo-exo-coordination. The larger ring cavity along with the flexible nature of L-2 may induce the weaker endocyclic complexation and contribute to exocyclic coordination as well. In NMR titration studies for the corresponding complex system, however, no evidence of exocyclic coordination was observed. Instead, L-1 and L-2 form a stable endocyclic 1 : 1 silver(I) nitrate complex, with a higher affinity for the former ligand.