Structural characterization of [HxRe3(CO)12]x-3 (x = 2, 3) by extended x-ray absorption fine structure spectroscopy

Extended X-ray absorption fine structure (EXAFS) measurements on the Re LnI edge have been used to elucidate the structures H3Re3(C0)12a nd [H2Re3(C0)12]-T. he data analysis is based on empirically determined EXAFS functions, including of OS~(CO)to~ a~c,c ount for the multiple scattering effects characteristic of metal carbonyls. The results confirm the of a triangular Re3 skeleton in each cluster, with the Re-Re bonds in the neutral cluster being of equal length (3.285). The disorder in the Re-Re shell characterizing the anionic cluster indicates that not all the Re-Re bonds are of equal, which implies the presence of bridging hydride ligands associated with the longer Re-Re bonds. Comparison of the data with published X-ray diffraction data characterizing [HRe3(CO),,12- shows a trend of decreasing Re-C distances increasing C-0 distances with increasing negative charge on the cluster, which is explained by r-back-bonding.