The Codimerizations of Styrene with Vinyl Compounds Catalyzed by Olefin-palladium(II) Chloride Complexes

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Abstract
The codimerization of styrene with vinyl compounds catalyzed by di-μ-chloro-dichlorobis(styrene)dipalladium(II), (Pd(C6H5CH=CH2)Cl2)2, was investigated in a homogeneous system under mild conditions. The reaction of styrene and methyl acrylate carried out at 50°C for 6 hr yielded 220% codimers, 169% dimers of methyl acrylate, and 18% dimers of styrene, on the basis of the palladium(II) used. The codimerizations of styrene with vinyl acetate and with methyl vinyl ketone gave 50% codimer and 125% codimers respectively. When nitroethylene and n-butyl vinyl ether were used as the vinyl compound, no codimers were formed. The codimerization of styrene-d3 with ethylene was also carried out. The reaction mechanism involving the five-coordinate hydridopalladiumolefin intermediate was proposed and discussed in the terms of the distribution of deuterium in the codimer of styrene-d3 and ethylene, the functional group effects of vinyl compounds, and solvent effects on the codimerization.