1. Tetravalent Uranium and Thorium Complexes: Elucidating Disparate Reactivities of An IV Cl 2 (An = U, Th) Supported by a Pyridine-Decorated Dianionic Ligand.
- Author
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Guo Y, Li X, Liu K, Hu K, Mei L, Chai Z, Gibson JK, Yu J, and Shi W
- Abstract
Although synthesis, reactivity, and bonding of U(IV) and Th(IV) complexes have been extensively studied, direct comparison of fully analogous compounds is rare. Herein, we report corresponding complexes 1-U and 1-Th , in which U(IV) and Th(IV) are supported by the tetradentate pyridine-decorated dianionic ligand N
2 NN' (1,1,1-trimethyl- N -(2-(((pyridin-2-ylmethyl)(2-((trimethylsilyl)amino)benzyl)amino)methyl)phenyl)silanamine). Although 1-U and 1-Th are structurally very similar, they display disparate reactivities with TMS3 SiK (tris(trimethylsilyl)silylpotassium). The reaction of (N2 NN')UCl2 ( 1-U ) and 1 equiv of TMS3 SiK in THF unexpectedly formed [Cl(N2 NN')U]2 O ( 2-U ) featuring an unusual bent U-O-U moiety. In contrast, a salt elimination reaction between (N2 NN')ThCl2 ( 1-Th ) and 1 equiv of TMS3 SiK led to thorium complex 2-Th , in which the pyridyl group has undergone a 1,4-addition nucleophilic attack. Complex 2-Th serves as a synthon for preparing dimetallic bis-azide complex 3-Th by reaction with NaN3 . The complexes were characterized by X-ray crystal diffraction, solution NMR, FT-IR, and elemental analysis. Computations of the formation mechanism of 2-U from 1-U suggest reduced U(III) as a key intermediate for promoting the cleavage of the C-O bonds of THF. The inaccessible nature of Th(III) as an intermediate oxidation state explains the very different reactivity of 1-Th versus 1-U . Given that reactants 1-U and 1-Th and products 2-U and 2-Th all comprise tetravalent actinides, this is an unusual case of very disparate reactivity despite no net change in the oxidation state. Complexes 2-U and 3-Th provide a basis for the synthesis of other dinuclear actinide complexes with novel reactivity and properties.- Published
- 2023
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