Ring-Opening Polymerization of Heterocycles with Palladium Insertion Catalysts:  Observation of a Multifunctional Polymerization Initiator

Abstract

The palladium insertion polymerization catalysts (bipy)Pd(CH3)L+OTf- have been found to mediate a second class of polymerization reaction: the ring-opening polymerization of heterocycles. Unlike traditional cationic ring-opening processes, this polymerization is found to proceed via an unusual series of metal-based reactions, including novel steps which allow the coupling of insertion monomers (CO and norbornene) with ring-opened polymers.

Zwitterionic Design Principle of Nickel(II) Catalysts for Carbonylative Polymerization of Cyclic Ethers

“…Typically, when epoxides were subjected to the cationic Ni II ‐ or Pd II ‐acetyl compounds under high‐pressure CO, oligoethers with an acetate ester end group were obtained, but not poly‐ or oligoesters. The same type of reactivity was also observed for tetrahydrofuran (THF) by Arndtsen and cleverly taken advantage of for the synthesis of poly(norbornene‐ block ‐THF) using cationic Pd complexes . Apparently, the initial attack by the cyclic ether on the acetyl‐Ni II+ and acetyl–Pd II+ bond indeed happens, but the resulting neutral Ni 0 and Pd 0 intermediate are separated from the acyloxonium cation in solution (Scheme ).…”

“…[19] Apparently,t he initial attack by the cyclic ether on the acetyl-Ni II+ and acetyl-Pd II+ bond indeed happens,b ut the resulting neutral Ni 0 and Pd 0 intermediate are separated from the acyloxonium cation in solution (Scheme 1). The results were disappointing without exception.…”

Ring-opening polymerization of cyclohexene oxide by a novel dicationic palladium catalyst

“…Nevertheless, only few reports exist on the use of cationic palladium species [43]. Based on our finding that the stable cationic palladium catalyst Pd(CH 3 CON-(2-pyridyl) 2 )(CH 3 CN) 2+ 2 (PF − 6 ) 2 (1) may be prepared from PdCl 2 (CH 3 CON-(2-pyridyl) 2 we were interested whether the Lewis acidic character of this compound would be pronounced enough to allow for the ROP of epoxides.…”

Zwitterionic Design Principle of Nickel(II) Catalysts for Carbonylative Polymerization of Cyclic Ethers

“…Ty pically,when epoxides were subjected to the cationic Ni II -o rP d II -acetyl compounds under high-pressure CO,o ligoethers with an acetate ester end group were obtained, but not poly-or oligoesters.T he same type of reactivity was also observed for tetrahydrofuran (THF) by Arndtsen and cleverly taken advantage of for the synthesis of poly(norbornene-block-THF) using cationic Pd complexes. [19] Apparently,t he initial attack by the cyclic ether on the acetyl-Ni II+ and acetyl-Pd II+ bond indeed happens,b ut the resulting neutral Ni 0 and Pd 0 intermediate are separated from the acyloxonium cation in solution (Scheme 1). Theacyloxonium cation then goes on by itself to initiate the cationic oligomerization of epoxide or polymerization of THF.…”