Terpolymerizations of CO2/propylene oxide (PO)/cyclohexene oxide (CHO), CO2/PO/1-hexene oxide (HO), and CO2/PO/1-butene oxide (BO) were carried out without the formation of cyclic carbonates and ether linkages with a cobalt(III) complex of a Salen-type ligand tethered by four quaternary ammonium salts (1). The activities were excellent, in the range of (0.62-1.6) x 10(6) g/mol-Co (TOF, 4400-14 000 h(-1)). In all three of terpolymerizations, the data for the PO mole fractions in the feed (f(PO)) and the polymers (F-PO) fit the Fineman-Ross plot well to determine the monomer reactivity ratios. The linear dependencies of the T-g's of the polymers on the mole fractions of the third monomers (F-CHO, F-HO, and F-BO) were observed with the relationships of "T-g(degrees C) = 81 x F-CHO + 40", "T-g(degrees C) = -62 x F-HO + 38", and "T-g (degrees C) = -27 x F-BO + 38", respectively. The decomposition temperature of the resin increased when the third monomer was employed. The GPC data indicated that the polymer chains grew man immortal passion from four 2,4-dinitrophenolates as well as the two 2.4-dinitrophenols in 1. High molecular weights (M-n) above 200 000 were attainable because of the high activities.