Reactive intermediates for the ethene homologation reaction on molybdena–silica catalysts

Abstract

Ethene has been selectively homologated to propene (3CC → 2CC—C) on reduced molybdena–silica at room temperature. The initial homologation activity was enhanced by grafting the methylene species on the surface with SnMe₄. Deuterated methane and cyclopropane were formed by reacting ²H₂ with the surface on which the ethene homologation had been carried out. These results clearly suggest that the ethene homologation proceeds through metal methylidene and metallocycle intermediates. The homologation accompanied the hydrogen exchange of ethene, which was considered to be a similar function to β-elimination of hydrogen from the metallocycle. [¹³C₂]propene was dominantly formed by the reaction of [¹³C₂]ethene on the CH₂ furnished surface. Taking account of the fact that the ethene metathesis proceeds 10³ times faster than the homologation, it was concluded that the propagating species for the homologation is different from that for the metathesis.