Polymerization of Alkyl Diazoacetates Initiated by Pd(Naphthoquinone)/Borate Systems: Dual Role of Naphthoquinones as Oxidant and Anionic Ligand for Generating Active Pd(II) Species

For polymerization of alkyl diazoacetates, the combination of a Pd complex bearing 1,4-naphthoquinone (NQ) or its derivatives as a ligand and borate, NaBPh4, was found to be an efficient initiating system. The polymerization of ethyl diazoacetate by a Pd(0) complex having two NQ molecules [Pd­(nq)2]...

Full description

Saved in:
Bibliographic Details
Published in:Macromolecules 2019-09, Vol.52 (18), p.6976-6987
Main Authors: Shimomoto, Hiroaki, Ichihara, Shohei, Hayashi, Hinano, Itoh, Tomomichi, Ihara, Eiji
Format: Article
Language:English
Citations: Items that this one cites
Items that cite this one
Online Access:Get full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:For polymerization of alkyl diazoacetates, the combination of a Pd complex bearing 1,4-naphthoquinone (NQ) or its derivatives as a ligand and borate, NaBPh4, was found to be an efficient initiating system. The polymerization of ethyl diazoacetate by a Pd(0) complex having two NQ molecules [Pd­(nq)2] with NaBPh4 proceeded to give poly­(ethoxycarbonylmethylene)­s with a relatively high molecular weight (up to M n = 36 kDa) in good yield (∼70%). This initiating system was also effective for polymerizing other diazoacetates, benzyl and cyclohexyl diazoacetates. In addition, in the presence of NaBPh4, a novel Pd­(II) complex bearing an anionic naphthoquinonyl ligand derived from 2,3-dichloro-1,4-naphthoquinone (dichlone), [Pd­(cod)­(Cl-nq)­Cl] (cod = 1,5-cyclooctadiene), which was newly prepared by treatment of a Pd(0) precursor, Pd2(dba)3·CHCl3 [dba = (E,E)-dibenzylideneacetone], with COD and dichlone, was capable of affording poly­(alkoxycarbonylmethylene)­s with much higher stereoregularity compared to the previously reported Pd-based initiating systems, despite a rather low polymer yield (∼20%). For both Pd­(nq)-based initiating systems, Pd–Ph species generated by transmetalation with NaBPh4 were responsible for the initiation of diazoacetates based on MALDI-TOF-MS analyses of the resulting polymers, and naphthoquinones played unique important dual roles as both an oxidant and an anionic ligand for generating the active Pd­(II) species.
ISSN:0024-9297
1520-5835
DOI:10.1021/acs.macromol.9b00857