The synthesis and characterization of anew tridentate amidomethylpyrrolidepyridine ligand (LigH(2)) and of the corresponding LigZr(NMe2)(2) Complex (1) are described. Characterization of I by single-crystal X-ray diffraction analysis showed a slightly distorted square-pyramidal geometry. Variable-temperature NMR analysis suggested that 1 adopts a C-s-symmetric structure in solution. Complex 1 in combination with Al'Bu2H and methylalumoxane afforded a highly active single-site catalyst for the polymerization of ethylene and propene, producing ultrahigh molecular weight linear polyethylene and isotactic polypropylene via an "enantiomorphic sites" mechanism of steric control.