Bidentate Phosphine-Assisted Synthesis of an All-Alkynyl-Protected Ag₇₄ Nanocluster

Determining the total structure of metal nanoparticles is vital to understand their properties. In this work, the first all-alkynyl-protected Ag nanocluster, Ag₇₄(C≡CPh)₄₄, was synthesized and structurally characterized by single crystal diffraction. Ag atoms are arranged in a Ag₄@Ag₂₂@Ag₄₈ three shell structure and all 44 phenylethynyl ligands coordinated with Ag in a μ₃ mode. In spite of being absent in nanocluster, ³¹P NMR study reveals that bidentate phosphine first reacts with Ag(I) to form a dinuclear complex, from which Ag atoms are then released to phenylethynyl ligands. This phosphine mediated strategy may find general application in synthesis of alkynyl-protected Ag nanoclusters.