Two novel alkynyl-protected silver-copper nanoclusters (Ph₄P)₂[Ag₂₂Cu₁₂(C≡CR)₂₈] and (Ph₄P)₃[Ag₄₂Cu₁₂Cl(C≡CR)₃₆] (Ag₂₂Cu₁₂ and Ag₄₂Cu₁₂Cl) were obtained by using a weak reducing agent diphenylsilane (Ph₂SiH₂). For the first time, a hybrid 55-atom two-shell Mackay icosahedron was found in Ag₄₂Cu₁₂Cl. The incorporation of a chloride in the metal icosahedron contributes to the stability of the cluster due to electronic and geometric factors.

Abstract

A facile strategy that directly reduces alkynyl-silver precursors and copper salts for the synthesis of bimetallic nanoclusters using the weak reducing agent Ph₂SiH₂ is demonstrated. Two alkynyl-protected concentric-shell nanoclusters, (Ph₄P)₂[Ag₂₂Cu₁₂(C≡CR)₂₈] and (Ph₄P)₃[Ag₄₂Cu₁₂Cl(C≡CR)₃₆] (Ag₂₂Cu₁₂ and Ag₄₂Cu₁₂Cl, R=bis(trifluoromethyl)phenyl), were successfully obtained and characterized by single-crystal X-ray diffraction and electro-spray ionization mass spectrometry. For the first time, a hybrid 55-atom two-shell Mackay icosahedron was found in Ag₄₂Cu₁₂Cl, which is icosahedral M₅₄Cl instead of M₅₅. The incorporation of a chloride in the metal icosahedron contributes to the stability of the cluster from both electronic and geometric aspects. Alkynyl ligands show various binding-modes including linear “RC≡C−Cu−C≡CR” staple motifs.