Structurally diverse copper complexes bearing NNO-tridentate Schiff-base derivatives as efficient catalysts for copolymerization of carbon dioxide and cyclohexene oxide

Inorg Chem. 2014 May 19;53(10):5109-16. doi: 10.1021/ic5002122. Epub 2014 May 6.

Abstract

Structurally diverse copper acetate complexes based on NNO-tridentate Schiff-base ligands were synthesized and characterized as mono-, di-, and trinuclear complexes with respect to varied ancillary ligands. Treatment of the ligand precursors (L(1)-H = 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-4-methylphenol, L(2)-H = 4-chloro-2-(1-((2-(dimethylamino)ethyl)imino)ethyl)phenol, and L(3)-H = 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-5-methylphenol) with Cu(OAc)2·H2O (1 equiv) in refluxing ethanol afforded five-coordinate mono- or bimetallic copper complexes ([(L(1))Cu(OAc)(H2O)] (1); [(L(2))Cu(OAc)(H2O)] (2); [(L(3))2Cu2(OAc)2] (3)) in high yields. Dinuclear copper acetate analogue [(L(1))2Cu2(OAc)2] (4) resulted from treatment of L(1)-H as the ligand precursor in refluxing anhydrous MeOH with equimolar proportions of metal acetate salt under a dry nitrogen atmosphere. However, a trinuclear complex, [(L(4))2Cu3(OAc)4] (5), was obtained on utilizing 2-(1-((2-(dimethylamino)ethyl)imino)ethyl)-5-methoxyphenol (L(4)-H) as the proligand under the same synthetic route of 1-3; this complex was also synthesized in the reaction of L(4)-H and copper(II) acetate monohydrate in the ratio of 2:3, giving a quantitative yield. All complexes are active catalysts for copolymerization of cyclohexene oxide (CHO) and CO2 without cocatalysts. In particular, dinuclear Cu complex 3 performed satisfactorily to produce polycarbonates with controllable molecular weights and high carbonate linkages. These copper complexes are the first examples that are effective for both CO2/CHO copolymerization and formation of polymers in a controlled fashion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amides / chemistry
  • Carbon Dioxide / chemistry*
  • Catalysis
  • Copper / chemistry*
  • Cyclohexenes / chemistry*
  • Imines / chemistry
  • Models, Molecular
  • Molecular Structure
  • Organometallic Compounds / chemistry*
  • Phenols / chemistry
  • Polymerization
  • Polymers / chemical synthesis
  • Polymers / chemistry
  • Schiff Bases / chemistry*

Substances

  • Amides
  • Cyclohexenes
  • Imines
  • Organometallic Compounds
  • Phenols
  • Polymers
  • Schiff Bases
  • Carbon Dioxide
  • cyclohexene oxide
  • Copper