A series of cobalt/Schiff base complexes, (R,R)-SalenCo(III)X [Salen = N,N'-bis(3,5-di-tert-butylsalicylidene)-1,2-di-phenylethylenediimine; X = OOCCF(3) (1), OOCCCl(3) (2), and OOCCH(3) (3)], were investigated for the alternating copolymerization of carbon dioxide with racemic propylene oxide in the presence of [PPN]CI ([PPN] = bis(triphenylphosphine)iminium). The effect of the axial group X of the complexes and the reaction conditions on the yield, the selectivity for poly(propylene carbonate) over propylene carbonate, and the polymer molecular weight for this transformation were investigated. A high molecular weight of 72.5 kg mol(-1) (Mn/Mw = 1.27, yield 76%) for the copolymer was achieved. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.