The synthesis and characterization of 15 new, unbridged metallocene dichloride complexes of the type (L)(Ind)ZrCl2, (L = omega-phenylalkyl substituted cyclopentadienyl or 1-phenylsilyl substituted indenyl; Ind = indenyl) and (L')(Flu)ZrCl2(L' = 1-benzyl substituted indenyl or 2-benzyl substituted indenyl; Flu = fluorenyl) are reported. After activation with methyl aluminoxane (MAO), these complexes are highly active catalysts for homogeneous ethylene polymerization. The influence of various substituents on the catalyst activities and the polymer properties are discussed.