Evidence of Hybrid Homogeneous–Heterogeneous Catalysis in a Pt/Au Heterobimetallic System

Abstract We report here our efforts towards understanding the catalytic species involved in a novel Pt/Au heterobimetallic system capable of efficiently catalysing the tandem cyclisation/C−X coupling reaction of heteroarylallenes with C‐ and N‐based nucleophiles. Our results confirm that homogeneous Au‐catalysis is involved at the beginning of the reaction to generate an intermediate that enters the second catalytic cycle in which hybrid homogeneous–heterogeneous catalysis by [Pt–Au] clusters could be responsible for the high efficiency. In this part of the cycle, [Pt–AuPPh3] homogeneous clusters (identified by 31P NMR analysis) seem to be aided by Pt–Au particles in the heterogeneous phase (supported by Hg poisoning, filtration experiments and characterisation of the possible catalytic species by several techniques, such us 31P NMR spectroscopy, inductively coupled plasma mass spectrometry, SEM and dynamic light scattering experiments). Here, full Pt‐to‐Au transmetallation was not observed contrary to the results with other bimetallic systems. Although a few examples of hybrid homogeneous–heterogeneous catalysis in monometallic systems exist, to the best of our knowledge, this is the first example of hybrid homogeneous–heterogeneous catalysis in systems involving two different metals.