Ring-Opening Copolymerization of 2-Aryl-1-methylenecyclopropanes with Carbon Monoxide Initiated by Pd–bpy Complexes

✍ Scribed by Sunwook Kim; Daisuke Takeuchi; Kohtaro Osakada

• Publisher: John Wiley and Sons
• Year: 2003
• Tongue: English
• Weight: 164 KB
• Volume: 204
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.200390035

✦ Synopsis

Abstract

[PdCl(Me)(bpy)] and a mixture of the complex with cocatalysts; NaBARF (BARF = [B{C~6~H~3~(CF~3~)~2~‐3,5}~4~]^−^), NaBF~4~, AgBARF, AgBF~4~, and AgOTf, catalyze the copolymerization of 2‐phenyl‐1‐methylenecyclopropane with carbon monoxide to produce a new polyketone accompanied by ring opening of the monomer. ^1^H and ^13^C{^1^H} NMR spectra indicate that the polymers have two isomeric repeating units in which the phenyl substituents occupy different positions. The molecular weights of the polyketones formed by the reactions with a [Pd]/[cocatalyst]/[2‐phenyl‐1‐methyleneyclopropane] ratio of 1:3:70 are in the range of M~n~ = 13 100–86 000. The polymer obtained by the reaction promoted by [PdCl(Me)(bpy)]/MBARF, where M = Ag or Na, shows a narrow molecular weight distribution, M~w~/M~n~ = 1.44 and 1.59, respectively. The catalysis is effective also for the ring‐opening copolymerization of 2‐aryl‐1‐methylenecyclopropanes bearing Me and F substituents on the phenyl ring. Isotope‐labeled experiments revealed the mechanism of the polymerization, which involves a 1,2‐insertion of the monomer into the Pd–acyl bond to produce a cyclopropylmethyl palladium intermediate, and subsequent β‐alkyl elimination to give the Pd–alkyl complex.

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