- The catalytic coupling of carbon dioxide with indene oxide utilizing (salen)Co(III)-2,4-dinitrophenoxide in the presence of an onium salt is presented. X-ray structural data for indene oxide monomer as well as cis-indene carbonate display near planarity of the fused cyclopentene and benzene rings. Low temperature (0 C) is required to selectively afford copolymer vs cyclic carbonate from the coupling reactions of CO(2) and indene oxide. The produced poly(indene carbonate) samples have molecular weights of up to 7100 Da, with corresponding glass transition temperatures of up to 134 C, the highest yet reported for polycarbonates produced from CO(2)/epoxides coupling. Poly(indene carbonate) is thermally stable up to 249 C. The polymerizations are well controlled, with PDI values 1.3.