Polyhydrido Copper Nanoclusters with a Hollow Icosahedral Core: [Cu₃₀H₁₈{E₂P(OR)₂}₁₂] (E=S or Se; R=<i>n</i>Pr, <i>i</i>Pr or <i>i</i>Bu)

Abstract

Although atomically precise polyhydrido copper nanoclusters are of prime interest for a variety of applications, they have so far remained scarce. Herein, this work describes the synthesis of a dithiophosphate-protected copper(I) hydride-rich nanocluster (NC), [Cu₃₀ H₁₈ {S₂ P(OnPr)₂ }₁₂ ] (1_H ), fully characterized by various spectroscopic methods and single-crystal X-ray diffraction. The X-ray structure of 1_H reveals an unprecedented central Cu₁₂ hollow icosahedron. Six faces of this icosahedron are capped by Cu₃ triangles, the whole Cu₃₀ core being wrapped by twelve dithiophosphate ligands and the whole cluster has ideal S₆ symmetry. The locations of the 18 hydrides in 1_H were ascertained by a single-crystal neutron diffraction study. They are composed of three types: capping μ₃ -H, interstitial μ₄ -H (seesaw) and μ₅ -H ligands (square pyramidal), in good agreement with the DFT simulations. The numbers of hydrides and ligand resonances in the ¹ H NMR spectrum of 1_H are in line with their coordination environment in the solid state, retaining the S₆ symmetry in solution. Furthermore, two new Se-protected polyhydrido copper nanoclusters, [Cu₃₀ H₁₈ {Se₂ P(OR)₂ }₁₂ ] (2_H : R=iPr 3_H : R=iBu) were synthesized from their sulfur relative 1_H via ligand displacement reaction and their X-ray structures feature the exceptional case where both the NC shape and size are fully conserved during the course of ligand exchange. DFT and TD-DFT calculations allow understanding the bonding and optical properties of clusters 1_H -3_H . In addition, the reaction of 1_H with [Pd(PPh₃ )₂ Cl₂ ] in the presence of terminal alkynes led to the formation of new bimetallic Cu-Pd alloy clusters [PdCu₁₄ H₂ {S₂ P(OnPr)₂ }₆ (C≡CR)₆ ] (4: R=Ph; 5: R=C₆ H₄ F).