Supported rhenium complexes were prepared from CH3Re(CO)(5) and dealuminated HY zeolite or NaY zeolite, each with a Si/Al atomic ratio of 30. The samples were characterized with infrared (IR) and extended X-ray absorption fine structure (EXAFS) spectroscopies. EXAFS data characterizing the sample formed by the reaction of CH3Re(CO)(5) with dealuminated HY zeolite show that the rhenium complexes were bonded to the zeolite frame, incorporating, on average, three carbonyl ligands per Re atom (as shown by Re-C and multiple-scattering Re-O EXAFS contributions). The I R spectra, consistent with this result, show that the supported rhenium carbonyls were bonded near aluminum sites of the zeolite, as shown by the decrease in intensity of the I R bands characterizing the acidic silanol groups resulting from the reaction of the rhenium carbonyl with the zeolite. This supported metal complex was characterized by narrow peaks in the nu(CO) region of the I R spectrum, indicating highly uniform species. In contrast, the species formed from CH3Re(CO)(5) on NaY zeolite lost fewer carbonyl ligands than those formed on HY zeolite and were significantly less uniform, as indicated by the greater breadth of the nu(CO) bands in the I R spectra. The results show the importance of zeolite H+ sites for the formation of uniform supported rhenium carbonyls from CH3Re(CO)(5); the formation of such uniform complexes did not occur on the NaY zeolite.