Octahedral group 4 bisphenolate ether complexes, activated by methylaluminoxane, were tested in propylene polymerization in the presence and absence of diethyl zinc. The resulting polypropylenes were analyzed thoroughly by means of differential scanning calorimetry and C-13 NMR techniques. Despite structural similarity of the Hf and Zr complexes, the performance in propylene polymerization differs significantly in terms of productivity, isospecificity, and propensity to incorporate specific regioerrors. These catalysts are capable of generating high-molecular weight polypropylene (M-n = 130,000-360,000 g/mol) with isotacticities [mmmm] up to 97% and melting points as high as 165 degrees C when very bulky ligands are used. C-13 NMR analysis revealed that the type and the number of regioerrors being incorporated into the polymer chain highly depend on the ligand and the metal. Polymerizations in the presence of diethyl zinc generate saturated low-molecular weight polypropylenes (M-n = 1700-9900 g/mol) and facilitated an end-group analysis, which revealed the presence of isobutyl and 2-methylbutyl groups. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 2604-2611, 2012