Stable Discrete Pt 1 (0) in Crown Ether with Ultra‐High Hydrosilylation Activity

Obtaining reduced discrete metal atoms that are stable in liquid solvents by in‐situ reduction of an ionic metal precursor has been a challenge until recently. A liquid surfactant polydimethylsiloxane‐polyethylene glycol (PDMS‐PEG) enabled the synthesis of stable discrete platinum atoms (Pt 1 ) by reducing Pt(IV) and Pt(II) salts. Here we report the successful preparation of discrete mononuclear platinum atoms (Pt 1 ) in a crown ether, [15]crown‐5, as a structurally much simpler solvent, and the prepared Pt 1 @[15]crown‐5 was demonstrated for ultra‐high catalytic activity and selectivity in hydrosilylation reactions. A combination of spectroscopic characterizations proves the reduced Pt species is Pt 1 (0) with partially positive charge. 195 Pt NMR and DFT calculation indicate the Pt 1 (0) is stabilized by the pseudo octahedral structure of ([15]crown‐5)PtCl − 2 H + 2 involving two adjacent oxygens from the crown ether ring, although the oxygens in the crown ether ring have been known to host and stabilize certain metal cations. The Pt 1 @[15]crown‐5 shows ultrahigh activity (TOF of 8.3×10 8  h −1 ) with excellent terminal adducts selectivity in catalytic olefin hydrosilylation. This catalyst was found to be highly stable under hydrosilylation conditions. For examples, the turnover number (TON) exceeded 1.0×10 9 for hydrosilylation between 1‐octene and (Me 3 SiO) 2 MeSiH without showing sign of deactivation; the TON exceeded 2.0×10 8 while the catalyst remained active for a catalytically more demanding reaction between styrene and (Me 3 SiO) 2 MeSiH.