Well-defined dinuclear silver phosphine complexes based on nitrogen donor ligand and their high efficient catalysis for A3-coupling reaction

Nitrogen donor ligands HL1, HL3, HL4 and their silver complexes 1·OTf–4·OTf are prepared and fully characterized. Treatment of HL1-HL4 with AgOTf (OTf− = triflato) in presence of base Et3N and co-ligand PPh3 affords dinuclear Ag(I) complexes [Ag2(L)(PPh3)2]·OTf (L = L1−, 1·OTf; L = L2−, 2·OTf; L = L3−, 3·OTf; L = L4−, 4·OTf), respectively. The solid structure displays L acts as bis(bidentate) ligand, bridging between two Ag(I) centres. The Ag⋯Ag interaction as well as other weak interactions, such as Ag⋯Brintermolecular for 1+, Ag⋯Brintramolecular for 2+, Ag⋯S for 3+ are observed. These complexes are applied in the A3-coupling reaction of aldehydes, alkynes and amines under mild conditions, and showed excellent catalytic efficiency and recyclability. 1 mol% catalyst loading gives 99% yield of propargylamines product in 0.15 h at 35 °C in open air atmosphere. 1·OTf can be recycled six times without noticeable less of the catalyst activity.