1417724-65-2Relevant academic research and scientific papers
Thorium(IV) and uranium(IV) halide complexes supported by bulky β-diketiminate ligands
Monreal, Marisa J.,Wright, Robert J.,Morris, David E.,Scott, Brian L.,Golden, Jeffery T.,Power, Philip P.,Kiplinger, Jaqueline L.
, p. 1423 - 1434 (2013/05/09)
The coordination behavior of the bulky β-diketiminate ligands N,N′-bis(2,6-diisopropylphenyl)pentane-2,4-diiminate (LMe) and N,N′-bis(2,6-diisopropylphenyl)-2,2-6,6-tetramethylheptane-3,5-diiminate (LtBu) toward ThX4(THF)4 (X = Br, I) and UCl4 has been investigated. The reaction between K[LMe] and ThX4(THF)4 (X = Br, I) afforded the mono(β-diketiminate)thorium(IV) halide complexes (LMe)ThX 3(THF) (X = Br (7), I (8)). The same reaction carried out with the more sterically demanding K[LtBu] gave (LtBu)ThBr 3(THF) (9) and (LtBu)ThI3 (11). All attempts to install two β-diketiminate ligands on thorium(IV) were unsuccessful, giving the mono(β-diketiminate)thorium(IV) halide complex and unreacted K[LMe] or K[LtBu]. However, complex 9 was shown to react with smaller anions such as K[C5H4Me] to give the mixed-ligand methylcyclopentadienyl β-diketiminate complex (L tBu)Th(C5H4Me)Br2 (10). Complexes 7-11 represent rare examples of thorium complexes featuring only one β-diketiminate ligand, and complexes 9-11 are the first examples of thorium and halide complexes supported by the LtBu framework. In a similar manner, both K[LMe] and K[LtBu] were shown to react with UCl4 to give the corresponding mono(β-diketiminate)uranium(IV) chloride complexes (LMe)UCl3(THF) (12) and (L tBu)UCl3 (13). Complex 13 represents the first example of a uranium complex featuring the LtBu framework. Efforts to prepare the bis(β-diketiminate)uranium(IV) complex (LMe) 2UCl2 by reacting 2 equiv of K[LMe] with UCl4 led instead to the interesting cationic diuranium complex [{(LMe)(Cl)U}2(μ-Cl)3][Cl] (14). Complexes 7-14 have been characterized by a combination of 1H and 13C{1H} NMR spectroscopy, elemental analysis, electrochemistry, and UV-visible-near-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 β-diketiminate ligand is symmetrically bound to the actinide metal in the LMe complexes and is asymmetrically bound to the actinide metal in the LtBu complexes. In all cases the actinide(IV) metal centers lie out of the plane of the β-diketiminate ligand NCCCN backbone by ～1-2 A. The electronic spectroscopy data on K[LMe], (LMe)ThI3(THF) (8), and (LMe)UCl 3(THF) (12) suggest relatively weak metal-(β-diketiminate) ligand bonding interactions, although small perturbations in the characteristics of the β-diketiminate π-π* bands with changes in the the metal ion are consistent with some metal-ligand orbital interactions. This new class of mono(β-diketiminate)thorium and -uranium halide complexes promises to provide a robust platform for developing new chemistry of the actinides.
