Bond lengths hydroxide complexes

For the unique rhenium complex Re(C0)3(C14H21N0)(C28H39N02), prepared from Re(CO)5Br or Re2(CO)10, 3,5-di-t-butylcatechol (3,5-DBCat), 3,5-di-/-butyl-l, 2-ben-zoquinone (3,5-DBBQ), and ammonium hydroxide [180], some structural features in bond lengths can be explained by delocalization of the oxygen anion and the phe-noxazinyl radical throughout the chelate ring 943 ... 

The Fourier transform moduli of EXAFS data of three silica samples that sorbed U(VI) appeared to be very similar (Fig. 3-5). The uranyl U=0 distance of 1.78 0.01 A is typical of U(VI) compounds. Shells for hydroxide coordinated in the equatorial plane appeared in the range 2.22 to 2.31 A, while bond distances for coordinated water molecules were observed from 2.43 to 2.51 A. The presence of a U-Si shell (between 3.1 and 3.3 A) in all samples investigated suggests the formation of inner-sphere uranyl surface complexes, and there was no evidence for a U-U shell, which would indicate surface precipitation or polynuclear uranyl species. The short U-Si bond length of about 3.2 A and coordination number of 1 at pH around 3 suggests bidentate complexation to a single silica atom. At pH 5, the coordination number of 2 for the Si shell suggests the coordination of the uranyl complex to two Si atoms (Sylwester et al., 2000). 

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