A Ligand-Free Pt3 Cluster Catalyzes the Markovnikov Hydrosilylation of Alkynes with up to 106 Turnover Frequencies

Abstract

[EN] The Pt-catalyzed hydrosilylation of alkynes is the procedure of choice to obtain vinylsilanes, and is claimed to be the most relevant application of Pt in organic synthesis. More than half a century after its discovery, only b-vinylsilanes (anti-Markovnikov addition) are obtained with simple Pt catalysts, whereas a-vinylsilanes (Markovnikov addition)remain elusive compounds.Here the catalysis of the Markovnikov hydrosilylation of terminal alkynes by Pt3clusters, in parts-per-million amounts, to give a wide variety of a-vinylsi-lanes in reasonable isolated yields and with turnover fre-quencies that can reach up to one million per hour is reported. Moreover, these a-vinylsilanes are reactive in well-stablished C@Cbond-forming cascade reactions, in which thecorresponding b-isomers are unreactive. Besides its efficiency and synthetic usefulness, this catalytic system is an excellent example of how the atom-by-atomaggregation of a catalytic metal leads to a different selectivity for a given reaction