The catalytic cleavage of carbon-carbon double bond in polychloroprene induced by Schwartz's reagent via chlorine self-assisted beta-alkyl elimination mechanism

摘要

The carbon-carbon double bonds (C=C) in polychloroprene (PCP) was broken down by Schwartz's reagent ([Cp2ZrClH](n)) under mild conditions. The reaction mechanism for cleaving C=C bonds in PCP was studied in detail. It was found that the cleavage pathway was chlorine self-assisted beta-alkyl elimination reaction, namely, alkyl elimination was promoted while chlorine in PCP was eliminated by releasing Cp2ZrCl2. The molecular weights of chain-scission products were controlled ranging from starting molecular weights of PCP to 0.2 kg mol(-1); at the same time, microstructures of chain-scission products were similar to chain structures of original PCP. In addition, chain-scission products could be chain-end functionalized by electrophiles quenching chain scission reaction. More importantly, efficient catalytic chain cleavage was achieved under the synergistic effect of ([Cp2ZrClH](n)) with both LiH and H-2.