Wolford Nikki J, Yu Xiaojuan, Bart Suzanne C, Autschbach Jochen, Neidig Michael L
Department of Chemistry, University of Rochester, Rochester, New York 14627, USA.
Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, USA.
Dalton Trans. 2020 Oct 27;49(41):14401-14410. doi: 10.1039/d0dt02929g.
The trivalent oxidation state of uranium has been shown to undergo unique reactivity, from its ability to activate a variety of small molecules to its role in the catalytic reduction of ethene to ethane amongst others. Central to this unique reactivity and ability to rationally design ligands for isotope separation is the underlying uranium electronic structure. While electronic structure studies of U(iv), U(v), and U(vi) have been extensive, by comparison, analogous studies of more reduced oxidation states such as U(iii) remains underdeveloped. Herein we report a combined MCD and EPR spectroscopic approach along with density functional theory and multireference wavefunction calculations to elucidate the effects of ligand perturbation in three uranium(iii) Tp* complexes. Overall, the experimental and computational insight suggests that the change in ligand environment across this series of U(iii) complexes resulted in only minor perturbations in the uranium electronic structure. This combined approach was also used to redefine the electronic ground state of a U(iii) complex with a redox non-innocent Bipy- ligand. Overall, these studies demonstrate the efficacy of the combined experimental and theoretical approach towards evaluating electronic structure and bonding in U(iii) complexes and provide important insight into the challenges in altering ligand environments to modify bonding and reactivity in uranium coordination chemistry.
铀的三价氧化态已被证明具有独特的反应活性，从其激活多种小分子的能力到它在催化乙烯还原为乙烷等反应中所起的作用等等。这种独特的反应活性以及为同位素分离合理设计配体的能力的核心在于潜在的铀电子结构。虽然对U(iv)、U(v)和U(vi)的电子结构研究已经很广泛，但相比之下，对U(iii)等更低氧化态的类似研究仍不充分。在此，我们报告了一种结合磁圆二色光谱（MCD）和电子顺磁共振光谱（EPR）的方法，以及密度泛函理论和多参考波函数计算，以阐明三种铀(iii) Tp*配合物中配体扰动的影响。总体而言，实验和计算结果表明，这一系列U(iii)配合物中配体环境的变化仅对铀电子结构产生了轻微扰动。这种联合方法还被用于重新定义一种具有氧化还原非惰性联吡啶配体的U(iii)配合物的电子基态。总体而言，这些研究证明了联合实验和理论方法在评估U(iii)配合物的电子结构和键合方面的有效性，并为在铀配位化学中改变配体环境以改变键合和反应活性所面临的挑战提供了重要见解。
