Deuterium kinetic isotope effects and H/D exchange in dimerization of acetylene with a Nieuwland catalyst in aqueous media

Deuterium kinetic isotope effects were observed in the dimerization of acetylene with a Nieuwland catalyst in an aqueous media, where the copper-acetylene and copper-monovinylacetylene (MVA) π-complexes were detected as intermediates by ¹H NMR. The copper-acetylene π-complex is responsible for an efficient H/D exchange between acetylene and proton (or deuteron) of water, which occurs rapidly with a Nieuwland catalyst. The deuterium kinetic isotope effects and the rapid H/D exchange reaction together with the detection of the copper-acetylene and copper-MVA π-complexes provide deeper insight into the catalytic mechanism of the Nieuwland catalysis for the dimerization of acetylene.