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. 2015 Jan 12:11:42-9.
doi: 10.3762/bjoc.11.7. eCollection 2015.

Anion effect controlling the selectivity in the zinc-catalysed copolymerisation of CO2 and cyclohexene oxide

Sait Elmas  1 , Muhammad Afzal Subhani  1 , Walter Leitner  2 , Thomas E Müller  1
Affiliations

Anion effect controlling the selectivity in the zinc-catalysed copolymerisation of CO2 and cyclohexene oxide

Sait Elmas et al. Beilstein J Org Chem. .

Abstract

The choice of the anion has a surprisingly strong effect on the incorporation of CO2 into the polymer obtained during the zinc-catalysed copolymerisation of CO2 and cyclohexene oxide. The product span ranges from polyethercarbonates, where short polyether sequences alternate with carbonate linkages, to polycarbonates with a strictly alternating sequence of the repeating units. Herein, we report on the influence of the coordination ability of the anion on the selectivity and kinetics of the copolymerisation reaction.

Keywords: CO2 chemistry; anion effect; carbon dioxide; copolymerisation; polyethercarbonate; zinc catalyst.

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Figures

Scheme 1
Scheme 1
Structural motif of two important types of catalysts and typical substrate specificity in the copolymerisation of CO2 and epoxides (*: end groups). Type I: binuclear complexes with a macrocyclic Robson-type ligand framework; Type II: mononuclear complexes with a Salen ligand.
Scheme 2
Scheme 2
Binuclear Zn(II) complexes [LZn2](CF3SO3)2 (1, KOP113) and [LZn2](p-TSO3)2 (2, KOP115) explored in this study (the numbers refer to the assignment of the NMR signals, see also Table 1).
Scheme 3
Scheme 3
Copolymerisation of CO2 and cyclohexene oxide (*: end groups of the polymer chain).
Figure 1
Figure 1
Time-resolved IR spectra of the copolymerisation of CO2 and CHO with catalyst 1 showing the formation of carbonate and ether groups in the polymer.
Figure 2
Figure 2
Time–concentration profile of the copolymerisation of CO2 and CHO in the presence of catalytic amounts of complex 1 and fit according to a first order kinetic in CO2 and in epoxide.
Figure 3
Figure 3
Carbonate region of the time-resolved IR spectra recorded during the copolymerisation of CO2 and cyclohexene with catalyst 2.
Figure 4
Figure 4
Time–concentration profile of the copolymerisation of CO2 and CHO in the presence of catalytic amounts of complex 2.
Scheme 4
Scheme 4
Proposed inner-sphere mechanism for the copolymerisation of CO2 and CHO with binuclear zinc complexes (1: X = CF3SO3, 2: X = p-TSO3).
See this image and copyright information in PMC

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