MECHANISM OF THE CATALYTIC ACTION OF THE MECHANOACTIVATED SALT K2PtCl4 IN THE GAS-PHASE HYDROCHLORINATION OF ACETYLENE

A heterogeneous catalyst for the hydrochlorination of acetylene by gaseous HCl is formed as a result of mechanical treatment of the solid salt K2PtCl4 in an atmosphere of acetylene, ethylene, or propylene by the formation of Pi complexes of platinum(II) as active centers in the surface layer under these conditions. The controlling stage of the catalytic reaction is chloroplatination of the _-coordinated acetylene by the HCl molecule. The reaction takes place as a concerted process, in which an intermediate _-chlorovinyl derivative of platinum(II), a complex of platinum with a coordination vacancy[PtC3l]^ and a new molecule of HCl are formed simultaneously with cleavage of the H—Cl and Pt—Cl bonds in the metal complex adjacent to the _-acetylene complex. The catalytic cycle closes with rapid dissociation of the organoplatinum intermediate by the action of HCl, giving the final product and the initial complex [PtCl4]2–.