A study on oxygen insertion in dinuclear silver cryptates

Abstract

Two novel silver(I) cryptates are reported in this paper. [Ag₂(L¹O)](ClO₄)₂·H₂O 1 and [Ag₂L¹](ClO₄)₂·1.5H₂O 2 were synthesized by the condensation of tris (3-aminopropyl) amine with m-phthalaldehyde in the presence of silver(I) ion, under aerobic and anaerobic conditions, respectively. (The ligand L¹O represents the oxygen insertion product of L¹.) Cryptates 1, 2, and their hydrogenated ligand H₁₂(L¹O) 3 and H₁₂L¹4 (obtained by reduction of the cryptates) were investigated by electrospray mass spectroscopy (ES-MS). 1 and 2 were also decomposed by HCl treatment and their products were separated and identified by HPLC and ES-MS. Our experiments show that cryptate 2 is able to activate dioxygen that results in quantitative aliphatic hydroxylation of L¹ on one of its HCN bonds. Crystal structure analysis shows an interesting difference between 1 and 2 in that 1 is an oxygenated and 2 is a non-oxygenated cryptate. Up to date, ligand hydroxylation has not been achieved in silver(I) complex–O₂ systems.