In this study, we investigate theselectivity for copolymer versuscyclic carbonate production from the coupling of isomeric forms ofbutene oxide with carbon dioxide in the presence of binary and bifunctionalcobalt(III) and chromium(III) salicylaldimine catalysts. Use of theless problematic 1-butene oxide has previously been reported to preferentiallyafford copolymer from its coupling with CO2. Of the epoxides, cis- and trans-2-butene oxide and isobuteneoxide, only cis-2-butene oxide was shown to selectivelyprovide polycarbonate, with both cobalt(III) catalysts being moreeffective than their chromium(III) analogues. The binary chromiumcatalyst system produced both cis- and trans-cyclic carbonates from the cycloaddition of CO2and cis-2-butene oxide, whereas, the corresponding cobalt(III)catalyst selectively yielded 75.4% copolymer at 40 °C with theremaining product being trans-cyclic carbonate. Inthis instance, the trans-cyclic carbonate resultsfrom copolymer degradation, consistent with the observation that depolymerizationof the copolymer derived from CO2and cis-2-butene oxide affords trans-cyclic carbonate exclusively.By way of contrast, both bifunctional catalysts were efficient atproducing copolymers with selectivities of 100% (40 °C) and 79%(70 °C) for the cobalt and chromium catalysts, respectively.The glass transition temperature (Tg)of poly(trans-2-butene carbonate) derived from thecompletely alternating copolymerization of CO2and cis-2-butene oxide was found to be 68 °C, some 30 deghigher than poly(propylene carbonate). Furthermore, it was shown tohave a significantly lower % elongation-to-break value than poly(propylenecarbonate). [ABSTRACT FROM AUTHOR]