Polymerization of ethyl and benzyl diazoacetates (EDA and BDA) initiated with π-allylPdCl-based systems [π-allylPdCl/NaBPh4, π-allylPdCl/NaBArF 4 (ArF = 3,5-{CF3}2C6H3), and π-allylPdCl] is described. Initiation efficiencies of the π-allylPdCl-based systems are much higher than those of the previously reported (NHC)­Pd/borate (NHC = N-heterocyclic carbene) systems, and the new systems are capable of polymerizing the alkyl diazoacetates at low temperatures (0 ∼ −20 °C), where the (NHC)­Pd/borate systems cannot initiate the polymerization. MALDI–TOF–MS analyses of the polymers obtained from EDA provide information for the chain-end structures of the polymers, based on which initiation and termination mechanisms are proposed. Interestingly, EDA polymerization by the π-allylPdCl-based systems in the presence of alcohols (EtOH, nPrOH, and nBuOH) or water was found to afford RO- or HO-initiated polymers as major products, as confirmed by MALDI–TOF–MS analyses.

(NHC)Pd/borate initiating systems (NHC = N-heterocyclic carbene) were applied for polymerization of alkyl diazoacetates with a variety of ester groups. The monomers with n-hexyl, cyclohexyl, benzyl, and cholesteryl group as an ester group were transformed into the corresponding poly(alkoxycarbonylmethylene)s with M n > 10 000. On the other hand, the polymerization of 1-adamantyl diazoacetate afforded low-M n polymers (M n < 4000), probably because of steric reasons. Copolymerization of a few comonomer combinations also proceeded successfully to give copolymers with M n > 20 000.