Results of propene polymerization in the presence of two known octahedral C-2-symmetric Zr complexes bearing tetradentate [ONNO]-type ligands are reported for the first time. Depending on the steric hindrance at the active metal, isotactic site-controlled or weakly syndiotactic chain-end-controlled polymers were obtained, in both cases via highly regioselective 1,2 (primary) monomer insertion. In this respect, the complexes mimic the behavior of the active Ti species on the surface of the heterogeneous Ziegler-Natta catalysts of which they might represent good structural models.