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The hydrochlorination of acetylene by gaseous HCl is catalyzed at room temperature on the surface of dry K 2 PtCl 4 subjected to mechanical preactivation in an acetylene atmosphere. The acetylene hydrochlorination product is formed by trans addition. The kinetic isotope effect (KIE) upon replacing HCl by DCl is 5 ± 1, which is much greater than the KIE found in the catalytic hydrochlorination of acetylene on the surface of mechanically preactivated K 2 PtCl 6 (1.9). This discrepancy suggests different reaction mechanisms in these two systems.

A heterogeneous catalyst for the hydrochlorination of acetylene by gaseous HCl is formed as a result of mechanical treatment of the solid salt K 2 PtCl 4 in an atmosphere of acetylene, ethylene, or propylene by the formation of p 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 p-coordinated acetylene by the HCl molecule. The reaction takes place as a concerted process, in which an intermediate b-chlorovinyl derivative of platinum(II), a complex of platinum with a coordination vacancy [ ] PtCl 3 * − , 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 p-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 [PtCl 4 ] 2-.The established unfavorable ecological situation in regions where the chemical industry is concentrated requires the development of novel processes and technologies directed toward a marked reduction in the toxicity and volumes of waste products from chemical manufacture. Such an approach, which has become known as green chemistry [1, 2], has developed vigorously in the last decade. One important aspect of green chemistry includes solid-phase mechanochemical synthesis and the chemistry of mechanically activated reactions involving the participation of solids [2]. Broad possibilities here are opened up by the methods of mechanochemistry in heterogeneous catalysis; it is possible, in particular, to bring compounds considered to catalytically inert into catalytic reactions (e.g., see [3][4][5]). The active centers of mechanically activated catalysts are usually related [6] to defects in the crystal structure. Such states are metastable on account of diffusion-retarded mobility in the solids, and their surface concentration can substantially exceed the equilibrium concentration, which distinguishes mechanically activated catalysts from "normal" heterogeneous catalysts.However, despite the obvious advantages the development of research in this region has been greatly restricted by the limitations of the data about methods for the transformation of mechanical energy to the structural defects in various types of crystal lattices. In order to resolve these problems it is appropriate to use relatively simple catalytic systems. As such a model reaction we chose the catalytic hydrochlorination of acetylene. It is known [7] that the activation of alkynes by metal complexes 314 0040-5760/06/4205-0314