Formation and hydrolysis of gas-phase [UO (R)] : R═CH , CH CH , CH═CH , and C H.

The goals of the present study were (a) to create positively charged organo-uranyl complexes with general formula [UO (R)] (eg, R═CH and CH CH ) by decarboxylation of [UO (O C─R)] precursors and (b) to identify the pathways by which the complexes, if formed, dissociate by collisional activation or otherwise react when exposed to gas-phase H O. Collision-induced dissociation (CID) of both [UO (O C─CH )] and [UO (O C─CH CH )] causes H transfer and elimination of a ketene to leave [UO (OH)] . However, CID of the alkoxides [UO (OCH CH )] and [UO (OCH CH CH )] produced [UO (CH )] and [UO (CH CH )] , respectively. Isolation of [UO (CH )] and [UO (CH CH )] for reaction with H O caused formation of [UO (H O)] by elimination of ·CH and ·CH CH : Hydrolysis was not observed. CID of the acrylate and benzoate versions of the complexes, [UO (O C─CH═CH )] and [UO (O C─C H )] , caused decarboxylation to leave [UO (CH═CH )] and [UO (C H )] , respectively. These organometallic species do react with H O to produce [UO (OH)] , and loss of the respective radicals to leave [UO (H O)] was not detected. Density functional theory calculations suggest that formation of [UO (OH)] , rather than the hydrated U O , cation is energetically favored regardless of the precursor ion. However, for the [UO (CH )] and [UO (CH CH )] precursors, the transition state energy for proton transfer to generate [UO (OH)] and the associated neutral alkanes is higher than the path involving direct elimination of the organic neutral to form [UO (H O)] . The situation is reversed for the [UO (CH═CH )] and [UO (C H )] precursors: The transition state for proton transfer is lower than the energy required for creation of [UO (H O)] by elimination of CH═CH or C H radical.