Poly(propylene carbonates) are prepared from propylene oxide and CO2 with less than 10% cyclic propylene carbonate by product using cobalt based catalysts of structure preferably in combination with salt cocatalyst, very preferably cocatalyst where the cation is PPN+ and the anion is Cl− or OBzF5−. Novel products include poly(propylene carbonates) having a stereoregularity greater than 90% and/or a regioregularity of greater than 90%.