Uranyl methoxide

Primary and sequential reactions of four small uranium oxide/hydroxide anions, U02, UO3, U04, and U03(0H), with methanol, were studied the experimental observations were evaluated by DFT, with the validity of the computational results—structures and reaction mechanisms—confirmed by isotopic labeling experiments (Michelini et al., 2010). The U02 ion was inert, whereas the other three oxoanions reacted with three methanol molecules via the addition or elimination of formaldehyde, water, or dihydrogen to ultimately produce inert uranyl methoxide anion complexes, [U 02(0CH3)2] or [U 02(0CH3)3] . The structure of the U04 ion reveals four discrete U—O bonds with no O—O bonding. Another notable feature of the DFT results that was verified by isotopic labeling is that the stmcture of... 

Through a series of experiments, Sessler and coworkers were able to determine a likely mechanism for the formation of complex 5.96. This mechanism, shown in Scheme 5.5.3, involves the initial coordination of uranyl cation to sapphyrin giving a complex such as 5.97 or 5.98. Addition of methanol (or methoxide anion) to one of... 

Figure 5.5.5 Single Crystal X-Ray Diffraction Structure of Uranyl Complex 5.96 Confirming the Formal Attack by Methoxide at the Macrocyclic C(10) Position.

Sapphyrins bearing peripheral substituents other than those present in 5.21 also react with uranyl cation in methanol to form complexes akin to 5.96. Analogous reactions, wherein the methoxide nucleophile is replaced by cyanide were also described by Sessler and coworkers. Unfortunately, when cyanide anion is used as the nucleophile, the reaction yield was very poor. It thus proved impossible to isolate and characterize fully the resulting uranyl complex. 

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