Cyclopenta[l]phenanthrene titanium trichloride and its 2-methyl and phenyl derivatives were synthesized; the crystalstructure of the 2-methyl-substituted complex was determined by X-ray diffraction analysis. In the presence of methylalurnoxane (MAO), these complexes give highly active catalysis for the syndiotactic polymerization of styrene; the 2-phenyl-substituted complex exceeds all previously