Efficient and Selective Conversion of Phosphine-Protected (MAu8)2+ (M = Pd, Pt) Superatoms to Thiolate-Protected (MAu12)6+ or Alkynyl-Protected (MAu12)4+ Superatoms via Hydride Doping

Abstract

An efficient and selective method was developed for the synthesis of bimetallic clusters, MAu₂₄L₁₈ (M = Pd or Pt; L = thiolates or alkynyls), by the reaction of Au(I)L oligomers with quasi-spherical superatoms [HMAu₈(PPh₃)₈]⁺ activated by hydride doping. This hydride-mediated conversion afforded previously known clusters MAu₂₄(SC₂H₄Ph)₁₈ having an icosahedral (M@Au₁₂)⁶⁺ core at ∼200 mg scale, with a yield of >50%, and was successfully applied to a variety of primary thiols with good yields. Although the application to secondary and tertiary thiolates was limited, the conversion produced the novel cluster [PdAu₂₃(ScC₆H₁₁)₁₇]⁰ having a poorly symmetrical, flattened (Pd@Au₁₂)⁶⁺ core. The conversion produced the new alkynyl-protected clusters [MAu₂₄(C≡CAr^F)₁₈]^2- (Ar^F = 3,5-(CF₃)₂C₆H₃) having an icosahedral (M@Au₁₂)⁴⁺ core, with a yield of >50%. The larger number of valence electrons in the M@Au₁₂ core protected by alkynyls is ascribed to an increase in attractive potential of the M@Au₁₂ core owing to the stronger electron-withdrawing nature of alkynyls than thiolates. This simple and versatile bottom-up approach will provide an opportunity to synthesize a variety of superatoms on a large scale for the promotion of materials science based on superatoms as building units.