Synthesis, Structure, Reactivity and Catalytic Implications of a Cationic, Acetylide‐Bridged Trigold–JohnPhos Species

The cationic complex [(JohnPhos–Au) 3 (acetylide)][SbF 6 ] (JohnPhos=(2‐biphenyl)di‐ tert ‐butylphosphine, L1) has been characterised structurally and features an acetylide–trigold(I)–JohnPhos system; the trinuclear–acetylide unit, coordinated to the monodentate bulk phosphines, adopts an unprecedented μ,η 1 ,η 2 ,η 1 coordination mode with an additional interaction between distal phenyl rings and gold centres. Other cationic σ,π‐[(gold(I)L1) 2 ] complexes have also been isolated. The reaction of trimethylsilylacetylene with various alcohols ( i PrOH, n BuOH, n ‐HexOH) catalysed by cationic [Au I L1][SbF 6 ] complexes in CH 2 Cl 2 at 50 °C led to the formation of acetaldehyde acetals with a high degree of chemo‐ and regioselectivity. The reaction mechanism was studied, and several organic and inorganic intermediates have been characterised. A comparative study with the analogous cationic [Cu I L1][PF 6 ] complex revealed different behaviour; the copper metal is lost from the coordination sphere leading to the formation of cationic vinylphosphonium and copper nanoparticles. Additionally, a new catalytic approach for the formation of this high‐value cationic vinylphosphonium has been established.