π‑AllylPdCl-Based Initiating Systems for Polymerization of Alkyl Diazoacetates: Initiation and Termination Mechanism Based on Analysis of Polymer Chain End Structures
- Publication date
- 2012
- Publisher
Abstract
Polymerization of ethyl and benzyl diazoacetates (EDA
and BDA) initiated with π-allylPdCl-based systems [π-allylPdCl/NaBPh<sub>4</sub>, π-allylPdCl/NaBAr<sup>F</sup><sub>4</sub> (Ar<sup>F</sup> = 3,5-{CF<sub>3</sub>}<sub>2</sub>C<sub>6</sub>H<sub>3</sub>), 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 = <i>N</i>-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