CEA, INAC, SCIB, Laboratoire de Reconnaissance Ionique et Chimie de Coordination, CEA-Grenoble, 38054 Grenoble, Cedex 09, France.
J Am Chem Soc. 2010 Jan 20;132(2):495-508. doi: 10.1021/ja9037164.
Stable complexes of pentavalent uranyl UO(2)(salan-(t)Bu(2))(py)K (3), [UO(2)(salan-(t)Bu(2))(py)K(18C6)] (4), and [UO(2)(salophen-(t)Bu(2))(thf)]K(thf)(2)}(n) (8) have been synthesized from the reaction of the complex {[UO(2)py(5)][KI(2)py(2)]}(n) (1) with the bulky amine-phenolate ligand potassium salt K(2)(salan-(t)Bu(2)) or the Schiff base ligand potassium salt K(2)(salophen-(t)Bu(2)) in pyridine. They were characterized by NMR, IR, elemental analysis, single crystal X-ray diffraction, UV-vis spectroscopy, cyclic voltammetry, low-temperature EPR, and variable-temperature magnetic susceptibility. X-ray diffraction shows that 3 and 8 are polymeric and 4 is monomeric. Crystals of the monomeric complex [U(V)O(2)(salan-(t)Bu(2))(py)][Cp*(2)Co], 6, were also isolated from the reduction of [U(VI)O(2)(salan-(t)Bu(2))(py)], 5, with Cp*(2)Co. Addition of crown ether to 1 afforded the highly soluble pyridine stable species [UO(2)py(5)]I.py (2). The measured redox potentials E(1/2) (U(VI)/U(V)) are significantly different for 2 (-0.91 and -0.46 V) in comparison with 3, 4, 5, 7 and 9 (in the range -1.65 to -1.82 V). Temperature-dependent magnetic susceptibility data are reported for 4 and 7 and give mu(eff) of 2.20 and 2.23 mu(B) at 300 K respectively, which is compared with a mu(eff) of 2.6(1) mu(B) (300 K) for 2. Complexes 1 and 2 are EPR silent (4 K) while a rhombic EPR signal (g(x) = 1.98; g(y) = 1.25; g(z) = 0.74 (at 4 K) was measured for 4. The magnetic and the EPR data can be qualitatively analyzed with a simple crystal field model where the f electron has a nonbonding character. However, the temperature dependence of the magnetic susceptibility data suggests that one or more excited states are relatively low-lying. DFT studies show unambiguously the presence of a significant covalent contribution to the metal-ligand interaction in these complexes leading to a significant lowering of the pi(u)*. The presence of a back-bonding interaction is likely to play a role in the observed solution stability of the [UO(2)(salan-(t)Bu(2))(py)K] and [UO(2)(salophen-(t)Bu(2))(py)K] complexes with respect to disproportionation and hydrolysis.
合成了一系列五价铀酰配合物，包括[UO 2 (salan-(t)Bu 2 )(py)K] n (3)、[UO 2 (salan-(t)Bu 2 )(py)K 18 C 6 ] (4)和[UO 2 (salophen-(t)Bu 2 )(thf)]K(thf) 2 (n) (8)，这些配合物是通过[UO 2 py 5 ]KI 2 py 2 与大体积胺酚盐钾盐 K 2 (salan-(t)Bu 2 )或席夫碱配体钾盐 K 2 (salophen-(t)Bu 2 )在吡啶中的反应得到的。通过 NMR、IR、元素分析、单晶 X 射线衍射、UV-vis 光谱、循环伏安法、低温 EPR 和变温磁化率对它们进行了表征。X 射线衍射表明 3 和 8 是聚合物，4 是单体。还从[U(VI)O 2 (salan-(t)Bu 2 )(py)] 5 的还原中分离出了单体复合物[U(V)O 2 (salan-(t)Bu 2 )(py)][Cp*(2)Co]，6。向 1 中加入冠醚可得到高溶解性的吡啶稳定物种[UO 2 py 5 ]I.py (2)。测量的氧化还原电位 E 1/2 (U(VI)/U(V))对于 2 (-0.91 和-0.46 V)与 3、4、5、7 和 9(在-1.65 到-1.82 V 范围内)有显著差异。报道了 4 和 7 的温度依赖磁化率数据，分别在 300 K 时给出了 2.20 和 2.23 μ B 的μ eff，与 2.6(1)μ B (300 K)的μ eff 相比。复合物 1 和 2 在 EPR 中是沉默的(4 K)，而 4 中测量到一个菱形 EPR 信号(g(x) = 1.98；g(y) = 1.25；g(z) = 0.74(在 4 K))。磁性和 EPR 数据可以用一个简单的晶体场模型进行定性分析，其中 f 电子具有非键合特性。然而，磁化率数据的温度依赖性表明，一个或多个激发态相对较低。DFT 研究清楚地表明，这些配合物中金属-配体相互作用存在显著的共价贡献，导致π(u)*显著降低。后键合相互作用可能在观察到的[UO 2 (salan-(t)Bu 2 )(py)K]和[UO 2 (salophen-(t)Bu 2 )(py)K]配合物相对于歧化和水解的溶液稳定性中起作用。
