Reduction-resistant and reduction-catalytic double-crown nickel nanoclusters

Area of Science:

• Nanomaterials Chemistry
• Coordination Chemistry
• Catalysis

Background:

• The Brust method is commonly used for synthesizing zero-valent metal nanoclusters.
• Nickel nanoclusters are of interest for catalytic applications.
• Understanding structure-property relationships in metal thiolate complexes is crucial.

Purpose of the Study:

• To synthesize zero-valent nickel nanoclusters using the Brust method.
• To characterize the unexpected nickel-phenylethanethiolate complex formed.
• To investigate its reduction resistance and catalytic activity.

Main Methods:

• Brust method for synthesis.
• Mass spectrometry (MS) for molecular weight determination.
• Thermal gravimetric analysis (TGA) for thermal stability.
• Single-crystal X-ray diffraction (XRD) for structural elucidation.
• X-ray photoelectron spectrometry (XPS) for surface chemistry.
• Catalytic reduction of 4-nitrophenol.

Main Results:

• Unexpected formation of a hexameric Ni(ii)-phenylethanethiolate complex, Ni₆(SCH₂CH₂Ph)₁₂, with a double-crown-like structure.
• The complex exhibits significant resistance to aqueous sodium borohydride (BH₄⁻).
• This reduction resistance is correlated with the unique double-crown structure.
• Ni₆(SCH₂CH₂Ph)₁₂ demonstrates superior catalytic activity compared to Au₂₅(SCH₂₂Ph)₁₈ for 4-nitrophenol reduction at 0 °C.

Conclusions:

• The Brust method can yield unexpected complex structures beyond zero-valent nanoclusters.
• The double-crown structure of Ni₆(SCH₂CH₂Ph)₁₂ is key to its unique reduction resistance.
• This nickel complex shows promising catalytic potential for 4-nitrophenol reduction, outperforming gold catalysts under specific conditions.
• Further research into less noble metal nanoclusters with unique structures is warranted.