Stable homogeneous silver(i) catalysts for the highly efficient cycloaddition of azides onto terminal alkynes in water†

Abstract

To develop stable and efficient silver(I) catalysts and evaluate the role of sulfur and phosphorus donor ligands in the catalytic cycloaddition of selected organic azides and alkynes (AAC), a series of mononuclear Ag(I) and heteronuclear Ag(I)–Fe(II) complexes were synthesized. The synthesis utilized phosphine and sulfur donors from the dialkyldithiophosphate and borate families, specifically Na[S₂H2B(mt)₂]. These complexes are designated as [(dppf)AgSP(S)(OⁱPr)₂] (1), [S₂H₂B(mt)₂Ag(μ-dppf)AgS₂H₂B(mt)₂] (2), [(dppf)Ag(μ-dppf)Ag(dppf)] (3), and [(dppe)AgS₂H₂B(mt)₂] (5). The complexes 1–5 were characterized using a combination of ¹H, ¹³C{¹H}, and ³¹P{¹H} NMR spectroscopy, as well as IR spectroscopy techniques. In two instances, single-crystal X-ray diffraction analysis was also employed. Complex 3 exhibited high catalytic activity and regioselectivity in the cycloaddition reaction conducted in water at 40 °C.