Hydroxy- and alkoxy-bridged dinuclear uranyl-Schiff base complexes: hydrolysis, transamination and extraction studies

作者：Bharara Mohan S; Heflin Kathryn; Tonks Stephen; Strawbridge Kara L; Gorden Anne E V^*

来源：Dalton Transactions, 2008, (22): 2966-2973.

DOI：10.1039/b800469b

The reaction of uranyl nitrate with 1,3-bis(salicylideneamino)-2-propanol (H(3)L1) and 1,3-bis(3,5-di-tert-butylsalicylideneamino)-2-propanol (H(3)L2) in the presence of triethylamine (Et(3)N) yielded hydroxy- and alkoxy-bridged dinuclear complexes; [(UO(2))(2)(L1)(OII)(MeOII)(2)]center dot(MeOII)(2) (1 center dot(MeOH)(2)) and [(UO(2))(2)(L2)(OH)(MeOH)(2)]center dot(MeOH)(2) (2 center dot(MeOH)(2)). The crystal structures of 1 center dot(DMF)(2) and 2 center dot(DMF)(2) exhibit an unsymmetrical central U(2)O(2) core involving bridging alkoxy- and hydroxy-oxygen atoms. The geometry around the uranium center in 1 center dot(DMF)(2) and 2 center dot(DMF)(2) is that of a distorted pentagonal bipyramid with the solvent molecule occupying the fifth coordination site. The flexible nature of the ligand backbone is more pronounced in 2 center dot(DMF)(2) compared to 1 center dot(DMF)(2), yielding two molecules per unit cell in different conformations. Under similar reaction conditions, using ethylenediamine as a base, the respective Salen-based uranyl compounds, [UO(2)(Salen)(MeOH)] (3) and [UO(2)( Bu(2)(t)-Salen)(MeOH)] (4) are obtained due to transamination of the ligand backbone. Complexes 1 center dot(MeOH)(2) and 2 center dot(MeOH)(2) when reacted with an excess of ethylenediamine failed to yield the respective Salen-based complexes, 3 and 4, respectively. The new compounds have been characterized using solution (NMR and UV-Vis) and solid-state (IR, X-ray crystallography) techniques. Hydrolysis of 1 center dot(MeOH)(2) and 2 center dot(MeOH)(2) in the pH range 1-14 was studied using UV-Vis spectroscopy and compared with the hydrolysis of 3 and [UO(2)(Salophen)(MeOH)] (5). A two-phase extraction study suggests quantitative removal of uranyl ions from the aqueous phase at higher pH conditions.

• 出版日期2008