DMAP/Cr(III) catalyst ratio:: The decisive factor for poly(propylene carbonate) formation in the coupling of CO2 and propylene oxide

Highly efficient formation of poly(propylene carbonate) can be achieved in the coupling of CO2 and propylene oxide assisted by 4-(N,N-dimethylamino)pyridine (DMAP) and catalyzed with salen chromium(III)chloride by using DMAP/Cr ratios of less than 2. Under these conditions a possible backbiting mechanism is suppressed, leading to only minor amounts of cyclic carbonate as a side product.