The successful alternating copolymerization of carbon dioxide and cyclohexene oxide was achieved by using a dinuclear zinc Schiff base complex, without forming cyclic carbonate. A remarkable effect of Lewis basic additives on the yield and selectivity of the product was demonstrated. Among the examined Lewis bases, 1,4-dioxane was the best additive, where the copolymerization with the dinuclear zinc Schiff base complex - 1,4-dioxane system produced selectively the perfectly alternating copolymer in high yield. (c) 2007 Elsevier Ltd. All rights reserved.