Theoretical Analysis of Factors Controlling the Nonalternating CO/C_2H_4 Copolymerization

摘要

A [P-O]Pd catalyst based on o-alkoxy derivatives of diphenylphosphinobenzene sulfonic acid (I) has recently been shown by Drent et al.(Chem.Commun.2002,9,964) to perform nonalternating CO/C_2H_4 copolymerization with subsequent incorporation of ethylene units into the polyketone chain.The origin of the nonalternation is investigated in a theoretical study of I,where calculated activation barriers and reaction heats of all involved elementary steps are used to generate a complete kinetic model.The kinetic model is able to account for the observed productivity and degree of nonalternation as a function of temperature.Consistent with the energy changes obtained for the real catalyst model,the selectivity toward a nonalternating distribution of both comonomers appears to be mainly a result of a strong destabilization of the Pd-acyl complex.