Abstract
Homodinuclear catalysts have good precedent for epoxide and carbon dioxide/anhydride copolymerizations; in contrast, so far pure heterodinuclear catalysts are unknown. The synthesis and properties of a heterodinuclear Zn(II)/Mg(II) complex coordinated by a symmetrical macrocyclic ligand are reported. It shows high polymerization selectivity, control, and significantly greater activity compared to either of the homodinuclear analogues or any combinations of them. Indeed, compared to a 50:50 mixture of the homodinuclear complexes, it shows 5 times (CO2/epoxide) or 40 times (anhydride/epoxide) greater activity.
Highlights
Homodinuclear catalysts have good precedent for epoxide and carbon dioxide/anhydride copolymerizations; in contrast, so far pure heterodinuclear catalysts are unknown
Significantly improved rates are observed for mixed metal complexes, as pioneered by Marks, Roesky (Ti/Zr and Al/Zr), and Harder (Al/Zr),[3] among others
We reported a range of high-activity homodinuclear catalysts, coordinated by a symmetrical macrocycle (Figure 1), for Ring-opening copolymerization (ROCOP) of epoxides/anhydrides/CO2.9d,i,11 Kinetic, DFT, and spectroscopic studies led to a proposed “chain shuttling” copolymerization pathway (Figure 1).9h,11a,12 each of the two metals has a distinct role in catalysis, and the growing polymer chain “shuttles” between the metals with each insertion
Summary
Homodinuclear catalysts have good precedent for epoxide and carbon dioxide/anhydride copolymerizations; in contrast, so far pure heterodinuclear catalysts are unknown. We reported a range of high-activity homodinuclear catalysts, coordinated by a symmetrical macrocycle (Figure 1), for ROCOP of epoxides/anhydrides/CO2.9d,i,11 Kinetic, DFT, and spectroscopic studies led to a proposed “chain shuttling” copolymerization pathway (Figure 1).9h,11a,12 each of the two metals has a distinct role in catalysis, and the growing polymer chain “shuttles” between the metals with each insertion.
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