rac-Dimethylsilylenebis(indenyl)zirconium dichloride was grafted onto commercial methyl aluminoxane modified silica (SMAO) at different loadings (0.1-1.5 wt % Zr/SMAO). Supported catalysts were evaluated in ethylene polymerization with isoprenylaluminum as a cocatalyst. The characterization of two supported catalysts bearing 0.3 and 0.8 wt % Zr/SiO2 by extended X-ray absorption fine structure indicated that the number and the intensity of the peaks beyond the coordination shell, associated with the next nearest neighbors, depended on the Zr concentration. For the catalyst with a higher Zr content, only one peak (2.8 angstrom) xas observed. The catalyst with 0.3 wt %, Zr/SMAO presented two small peaks at 2.8 and 3.8 angstrom. Polymers produced with the Supported catalysts presented lower crystallinity and higher molar mass and polydispersity values in comparison to that produced by the homogeneous one. Gel permeation chromatogram deconvolution Suggested the presence Of four catalyst sites for the supported systems. (c) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 112: 563-571, 2009