Bai Zhuanling, Martelles Madeline C, Sperling Joseph M, Albrecht Thomas E
Department of Chemistry, Nuclear Science & Engineering Center, Colorado School of Mines Golden Colorado 80401 USA
Chem Sci. 2025 May 6. doi: 10.1039/d5sc01808k.
A trivalent plutonium-pyrazinyl-tetrazolate complex Na[Pu(Hdtp)(dtp)(HO)]·9HO (Pu_dtp, Hdtp = 2,3-di-1-tetrazol-5-ylpyrazine) was synthesized through metathesis reaction of plutonium bromide and Na(dtp)·2HO in water. This structure is particularly notable among complexes formed by trivalent f-elements and the dtp ligand in aqueous media. In contrast to other trivalent f-elements, including all Ln (with the exception of Pm) and Cm, preferentially coordinated with eight water molecules rather than the nitrogen donors of the dtp ligand, Pu exhibits a distinct affinity for nitrogen coordination. This observation provides strong evidence that the 5f electrons in Pu are more delocalized than other studied trivalent f-elements. In Pu_dtp, three distinct Pu(iii)-N bonds are present: one Pu(iii)-N5 from pyrazinyl, one Pu(iii)-N4 from the least electronegative nitrogen in the tetrazolate, and three Pu(iii)-N1/N2/N3 from the most electronegative nitrogens in the tetrazolate. Experimental Pu(iii)-N bond lengths, Wiberg bond indices (WBI), natural localized molecular orbitals (NLMO), quantum theory of atoms in molecules (QTAIM), and energy decomposition analysis (EDA), reveal a covalency trend: Pu(iii)-N from the most electronegative nitrogen in tetrazolate > Pu(iii)-N from the least electronegative nitrogen in tetrazolate > Pu(iii)-N from pyrazinyl. This trend arises from the increased negative charge on the most electronegative nitrogen atoms in the tetrazolate ring, enhancing electrostatic Pu-N1/N2/N3 interactions. These stronger electrostatic interactions lead to shorter bond lengths, thereby enhancing orbital overlap and greater covalency, compared to the less electronegative nitrogen in tetrazolate (Pu-N4) and the neutral pyrazinyl nitrogen (Pu-N5).
通过溴化钚与 Na(dtp)·2H₂O 在水中的复分解反应合成了一种三价钚 - 吡嗪基 - 四唑配合物 Na[Pu(Hdtp)(dtp)(H₂O)]·9H₂O（Pu_dtp，Hdtp = 2,3 - 二 - 1 - 四唑 - 5 - 基吡嗪）。在水介质中由三价 f 元素与 dtp 配体形成的配合物中，这种结构尤为显著。与其他三价 f 元素（包括所有镧系元素（除钷外）和锔）优先与八个水分子配位而非 dtp 配体的氮供体不同，钚对氮配位表现出明显的亲和力。这一观察结果提供了有力证据，表明钚中的 5f 电子比其他研究的三价 f 元素更离域。在 Pu_dtp 中，存在三种不同的 Pu(iii)-N 键：一个来自吡嗪基的 Pu(iii)-N5，一个来自四唑中电负性最小的氮的 Pu(iii)-N4，以及三个来自四唑中电负性最大的氮的 Pu(iii)-N1/N2/N3。实验测得的 Pu(iii)-N 键长、维伯格键指数（WBI）、自然定域分子轨道（NLMO）、分子中的原子量子理论（QTAIM）和能量分解分析（EDA）揭示了一种共价性趋势：来自四唑中电负性最大的氮的 Pu(iii)-N > 来自四唑中电负性最小的氮的 Pu(iii)-N > 来自吡嗪基的 Pu(iii)-N。这种趋势源于四唑环中电负性最大的氮原子上负电荷的增加，增强了静电 Pu-N1/N2/N3 相互作用。与四唑中电负性较小的氮（Pu-N4）和中性吡嗪基氮（Pu-N5）相比，这些更强的静电相互作用导致键长更短，从而增强了轨道重叠并具有更大的共价性。
