Thorium(IV) and Uranium(IV) Halide Complexes Supported by Bulky 尾-Diketiminate Ligands

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• 作者：Marisa J. Monreal ; Robert J. Wright ; David E. Morris ; Brian L. Scott ; Jeffery T. Golden ; Philip P. Power ; Jaqueline L. Kiplinger
• 刊名：Organometallics
• 出版年：2013
• 出版时间：March 11, 2013
• 年：2013
• 卷：32
• 期：5
• 页码：1423-1434
• 全文大小：488K
• 年卷期：v.32,no.5(March 11, 2013)
• ISSN：1520-6041

文摘

The coordination behavior of the bulky 尾-diketiminate ligands N,N鈥?bis(2,6-diisopropylphenyl)pentane-2,4-diiminate (L^Me) and N,N鈥?bis(2,6-diisopropylphenyl)-2,2鈥?,6-tetramethylheptane-3,5-diiminate (L^tBu) toward ThX₄(THF)₄ (X = Br, I) and UCl₄ has been investigated. The reaction between K[L^Me] and ThX₄(THF)₄ (X = Br, I) afforded the mono(尾-diketiminate)thorium(IV) halide complexes (L^Me)ThX₃(THF) (X = Br (7), I (8)). The same reaction carried out with the more sterically demanding K[L^tBu] gave (L^tBu)ThBr₃(THF) (9) and (L^tBu)ThI₃ (11). All attempts to install two 尾-diketiminate ligands on thorium(IV) were unsuccessful, giving the mono(尾-diketiminate)thorium(IV) halide complex and unreacted K[L^Me] or K[L^tBu]. However, complex 9 was shown to react with smaller anions such as K[C₅H₄Me] to give the mixed-ligand methylcyclopentadienyl 尾-diketiminate complex (L^tBu)Th(C₅H₄Me)Br₂ (10). Complexes 7鈥?b>11 represent rare examples of thorium complexes featuring only one 尾-diketiminate ligand, and complexes 9鈥?b>11 are the first examples of thorium and halide complexes supported by the L^tBu framework. In a similar manner, both K[L^Me] and K[L^tBu] were shown to react with UCl₄ to give the corresponding mono(尾-diketiminate)uranium(IV) chloride complexes (L^Me)UCl₃(THF) (12) and (L^tBu)UCl₃ (13). Complex 13 represents the first example of a uranium complex featuring the L^tBu framework. Efforts to prepare the bis(尾-diketiminate)uranium(IV) complex (L^Me)₂UCl₂ by reacting 2 equiv of K[L^Me] with UCl₄ led instead to the interesting cationic diuranium complex [{(L^Me)(Cl)U}₂(渭-Cl)₃][Cl] (14). Complexes 7鈥?b>14 have been characterized by a combination of ¹H and ¹³C{¹H} NMR spectroscopy, elemental analysis, electrochemistry, and UV鈥搗isible鈥搉ear-IR spectroscopy. Several complexes have also been characterized by X-ray crystallography, and a discussion of their structures is presented. NMR spectroscopy and the X-ray structures demonstrate that the 尾-diketiminate ligand is symmetrically bound to the actinide metal in the L^Me complexes and is asymmetrically bound to the actinide metal in the L^tBu complexes. In all cases the actinide(IV) metal centers lie out of the plane of the 尾-diketiminate ligand NCCCN backbone by 1鈥? 脜. The electronic spectroscopy data on K[L^Me], (L^Me)ThI₃(THF) (8), and (L^Me)UCl₃(THF) (12) suggest relatively weak metal鈥?尾-diketiminate) ligand bonding interactions, although small perturbations in the characteristics of the 尾-diketiminate 蟺鈥撓€* bands with changes in the the metal ion are consistent with some metal鈥搇igand orbital interactions. This new class of mono(尾-diketiminate)thorium and -uranium halide complexes promises to provide a robust platform for developing new chemistry of the actinides.