Mixed AuPd Nanoparticles as Highly Active Catalysts for Alkyne Z‐Semihydrogenation

A method for the preparation of mixed AuPd nanoparticles that are used as catalysts for selective alkyne Z‐semihydrogenation is described. It is shown that the corresponding monometallic Pd nanoparticles display a lower activity, documenting the cooperative effect exerted by the two metals. These mixed AuPd nanoalloys are readily prepared by irradiation of the corresponding precursor salts in the presence of photoactive polymers or commercially available photoinitiators as reducing and stabilizing agents. Alkyne semihydrogenation using these catalyst systems with H2 proceeds in high yield (up to 97 % yield of isolated product) and excellent Z‐selectivity (up to 99 %). Hydrogenations work on larger scale and the hybrid catalyst can be recovered and reused by simple centrifugation. Two metals are better than one! Readily prepared mixed AuPd nanoparticles with a diameter of around 2.6 nm show high catalyst activity for the selective Z‐semihydrogenation of various alkynes. The corresponding monometallic Au nanoparticles show no activity and the monometallic Pd system displays significantly lower activity documenting the cooperative effect of the two metals.