C-13 NMR spectroscopy is used to characterize the microstructure of polypropylene (PP) obtained using a nickel alpha-keto-beta-diimine initiator activated with methylaluminoxane (MAO) at different reaction temperatures (T-rxn). The product prepared at -20 degrees C has structural features that resemble an ethylene-propylene copolymer. We find that the main sequences present in this sample arise as a result of normal 1,2-insertion and that propylene sequences are predominantly isotactic (m = 88%, mmmm = 63%). There is also evidence of ethylene-like sequences as a result of 3,1-enchainment, and from 2,1-insertion. A reduction in T-rxn to -60 degrees C results in a polymer that has undetectable regioirregularities and is highly isotactic (m = 93%, mmmm = 85%). Moreover, the application of stereo propagation models gives indication that the isospecificity is a result of enantiomorphic site control.