Windorff Cory J, MacDonald Matthew R, Meihaus Katie R, Ziller Joseph W, Long Jeffrey R, Evans William J
Department of Chemistry, University of California-Irvine, Irvine, CA 92697 (USA).
Department of Chemistry, University of California-Berkeley, Berkeley, CA 94720 (USA).
Chemistry. 2016 Jan 11;22(2):772-82. doi: 10.1002/chem.201503583. Epub 2015 Dec 4.
The synthesis of new molecular complexes of U(2+) has been pursued to make comparisons in structure, physical properties, and reactivity with the first U(2+) complex, [K(2.2.2-cryptand)][Cp'3 U], 1 (Cp'=C5 H4 SiMe3 ). Reduction of Cp''3 U [Cp''=C5 H3 (SiMe3 )2 ] with KC8 in the presence of 2.2.2-cryptand or 18-crown-6 generates [K(2.2.2-cryptand)][Cp''3 U], 2-K(crypt), or [K(18-crown-6)(THF)2 ][Cp''3 U], 2-K(18c6), respectively. The UV/Vis spectra of 2-K and 1 are similar, and they are much more intense than those of U(3+) analogues. Variable temperature magnetic susceptibility data for 1 and 2-K(crypt) reveal lower room temperature χM T values relative to the experimental values for the 5f(3) U(3+) precursors. Stability studies monitored by UV/Vis spectroscopy show that 2-K(crypt) and 2-K(18c6) have t1/2 values of 20 and 15 h at room temperature, respectively, vs. 1.5 h for 1. Complex 2-K(18c6) reacts with H2 or PhSiH3 to form the uranium hydride, [K(18-crown-6)(THF)2 ][Cp''3 UH], 3. Complexes 1 and 2-K(18c6) both reduce cyclooctatetraene to form uranocene, (C8 H8 )2 U, as well as the U(3+) byproducts [K(2.2.2-cryptand)][Cp'4 U], 4, and Cp''3 U, respectively.
人们一直致力于合成新的U(2+)分子配合物，以便在结构、物理性质和反应活性方面与首个U(2+)配合物[K(2.2.2-穴醚)][Cp'3U]（1，Cp'=C5H4SiMe3）进行比较。在2.2.2-穴醚或18-冠-6存在的情况下，用KC8还原Cp''3U[Cp''=C5H3(SiMe3)2]，分别生成[K(2.2.2-穴醚)][Cp''3U]（2-K(穴)）或[K(18-冠-6)(THF)2][Cp''3U]（2-K(18c6)）。2-K和1的紫外/可见光谱相似，且比U(3+)类似物的光谱强度大得多。1和2-K(穴)的变温磁化率数据显示，相对于5f(3)U(3+)前体的实验值，其室温χMT值较低。通过紫外/可见光谱监测的稳定性研究表明，2-K(穴)和2-K(18c6)在室温下的半衰期分别为20小时和15小时，而1为1.5小时。配合物2-K(18c6)与H2或PhSiH3反应生成氢化铀[K(18-冠-6)(THF)2][Cp''3UH]（3）。配合物1和2-K(18c6)都能还原环辛四烯形成铀茂(C8H8)2U，以及分别生成U(3+)副产物[K(2.2.2-穴醚)][Cp'4U]（4）和Cp''3U。
