Neptunium is an actinide element sourced from anthropogenic production, and, unlike naturally abundant uranium, its coordination chemistry is not well developed in all accessible oxidation states. High-valent neptunium generally requires stabilization from at least one metal–ligand multiple bond, and departing from this structural motif poses a considerable challenge. Here we report a tetrahedral molecular neptunium(V) complex ([Np⁵⁺(NPC)₄][B(ArF₅)₄], 1-Np) (NPC = [NP^tBu(pyrr)₂]⁻; ^tBu = C(CH₃)₃; pyrr = pyrrolidinyl (N(C₂H₄)₂); B(ArF₅)₄ = tetrakis(2,3,4,5,6-pentafluourophenyl)borate). Single-crystal X-ray diffraction, solution-state spectroscopy and density functional theory studies of 1-Np and the product of its proton-coupled electron transfer (PCET) reaction, 2-Np, demonstrate the unique bonding that stabilizes this reactive ion and establishes the thermochemical and kinetic parameters of PCET in a condensed-phase transuranic complex. The isolation of this four-coordinate, neptunium(V) complex reveals a fundamental reaction pathway in transuranic chemistry.

镎是一种来自人类生产的锕系元素，与天然丰富的铀不同，它的配位化学在所有可接近的氧化态下都没有得到很好的发展。高价镎通常需要至少一个金属-配体多重键的稳定，而偏离这一结构基序带来了相当大的挑战。在这里，我们报道了一种四面体分子镎(V)配合物 ([Np ⁵⁺ (NPC) ₄ ][B(ArF ₅ ) ₄ ], 1-Np) (NPC = [NP ^t Bu(pyrr) ₂ ] ⁻ ; ^t Bu = C(CH ₃ ) ₃；pyrr = 吡咯烷基(N(C ₂ H ₄ ) ₂ )；B(ArF ₅ ) ₄  = 四(2,3,4,5,6-五氟苯基)硼酸酯)。对 1-Np 及其质子耦合电子转移 (PCET) 反应产物 2-Np 的单晶 X 射线衍射、溶液态光谱和密度泛函理论研究，证明了稳定该反应离子的独特键合，建立了凝聚相超铀络合物中 PCET 的热化学和动力学参数。这种四配位镎 (V) 络合物的分离揭示了超铀化学中的基本反应途径。