Efficient Magnesium Catalysts
for the Copolymerization
of Epoxides and CO<sub>2</sub>; Using Water to Synthesize Polycarbonate
Polyols
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Abstract
The synthesis and characterization of three highly active
dimagnesium
catalysts for the copolymerization of cyclohexene oxide and carbon
dioxide, active under just 1 atm of carbon dioxide pressure, are reported.
The catalysts have turnover numbers up to 6000 and turnover frequencies
of up to 750 h<sup>–1</sup>. These values are, respectively,
75 and 20 times higher than those of the other three known magnesium
catalysts. Furthermore, the catalysts operate at 1/500th the loading
of the best reported magnesium catalyst. The catalyst selectivities
are excellent, yielding polymers with 99% carbonate repeat units and
>99% selectivity for copolymer. Using a dimagnesium bis(trifluoroacetate)
catalyst, and water as a renewable chain transfer reagent, poly(cyclohexene
carbonate) polyols are synthesized with high selectivity