Soluble Platinum Nanoparticles Ligated by Long‐Chain N‐Heterocyclic Carbenes as Catalysts

Soluble platinum nanoparticles (Pt NPs) ligated by two different long‐chain N‐heterocyclic carbenes (LC‐IPr and LC‐IMe) were synthesized and fully characterized by TEM, high‐resolution TEM, wide‐angle X‐ray scattering (WAXS), X‐ray photoelectron spectroscopy (XPS), and solution NMR. The surface chemistry of these NPs (Pt@LC‐IPr and Pt@LC‐IMe) was investigated by FT‐IR and solid state NMR using CO as a probe molecule. A clear influence of the bulkiness of the N‐substituents on the size, surface state, and catalytic activity of these Pt NPs was observed. While Pt@LC‐IMe showed no activity in the hydroboration of phenylacetylene, Pt@LC‐IPr revealed good selectivity for the trans‐isomer, which may be supported by a homogeneous species. This is the first example of hydroboration of acetylenes catalyzed by non‐supported Pt NPs. Telling a tall tail: soluble platinum nanoparticles ligated by two different long‐chain N‐heterocyclic carbenes (Pt@LC‐IPr and Pt@LC‐IMe) show marked differences in their catalytic activity depending on the bulkiness of the N‐substituents. While Pt@LC‐IMe behaves similarly to heterogeneous catalysts, the catalytic activity of Pt@LC‐IPr parallels that of molecular complexes in the hydroboration of phenylacetylene.