Four new donor-functionalized ansa-zirconocenes have been synthesized from the XMeSiCp2ZrCl2 and X2SiCp2ZrCl2 general formula (where X = (CH2)(3)OEt, C8H4SCH2OMe, and CH2(2-MeO-3-Me-C6H3)). In each of these metallocenes, alkoxy groups are linked by a three-carbon chain to the silicon atom. To study the influence of the functionalized side chains, these metallocenes were activated with methylalumoxane (MAO) and utilized in solution polymerization of ethylene. The molecular weight distributions of the polymers formed show a bimodal shape which can be described as a superposition of two Schultz-Flory distributions, synonymous to at least two different catalytic species. Unimodal polymers with M-w/M-n=2 were formed with the Me2SiCp2ZrCl2/MAO catalyst system, indicating that the unusual bimodal molecular weight distributions are due to the functionalized side chains tethered to the Si-bridge.