Santos Marta, de Matos António Pires, Marçalo Joaquim, Gibson John K, Haire Richard G, Tyagi Rajni, Pitzer Russell M
Departamento de Química, Instituto Tecnológico e Nuclear, Sacavém, Portugal.
J Phys Chem A. 2006 May 4;110(17):5751-9. doi: 10.1021/jp057297d.
Oxidation reactions of bare and ligated, monopositive, and dipositive Pa ions in the gas phase were studied by Fourier transform ion cyclotron resonance mass spectrometry. Seven oxidants were employed, ranging from the thermodynamically robust N(2)O to the relatively weak CH(2)O-all oxidized Pa(+) to PaO(+) and PaO(+) to PaO(2)(+). On the basis of experimental observations, it was established that D[Pa(+)-O] and D[OPa(+)-O] > or = 751 kJ mol(-1). Estimates for D[Pa(+)-O], D[OPa(+)-O], IE[PaO], and IE[PaO(2)] were also obtained. The seven oxidants reacted with Pa(2+) to produce PaO(2+), indicating that D[Pa(2+)-O] > or = 751 kJ mol(-1). A particularly notable finding was the oxidation of PaO(2+) by N(2)O to PaO(2)(2+), a species, which formally comprises Pa(VI). Collision-induced dissociation of PaO(2)(2+) suggested the protactinyl connectivity, {O-Pa-O}(2+). The experimentally determined IE[PaO(2)(+)] approximately 16.6 eV is in agreement with self-consistent-field and configuration interaction calculations for PaO(2)(+) and PaO(2)(2+). These calculations provide insights into the electronic structures of these ions and indicate the participation of 5f orbitals in bonding and a partial "6p hole" in the case of protactinyl. It was found that PaO(2)(2+) catalyzes the oxidation of CO by N(2)O-such O atom transport via a dipositive metal oxide ion is distinctive. It was also observed that PaO(2)(2+) is capable of activating H(2) to form the stable PaO(2)H(2+) ion.
采用傅里叶变换离子回旋共振质谱法研究了气相中裸露的、单正价和双正价镤离子以及配位后的镤离子的氧化反应。使用了七种氧化剂，从热力学稳定的N₂O到相对较弱的CH₂O，所有氧化剂都能将Pa⁺氧化为PaO⁺，将PaO⁺氧化为PaO₂⁺。基于实验观察，确定了D[Pa⁺-O]和D[OPa⁺-O]≥751 kJ mol⁻¹。还获得了D[Pa⁺-O]、D[OPa⁺-O]、IE[PaO]和IE[PaO₂]的估计值。七种氧化剂与Pa²⁺反应生成PaO₂⁺，表明D[Pa²⁺-O]≥751 kJ mol⁻¹。一个特别显著的发现是N₂O将PaO₂⁺氧化为PaO₂²⁺，该物种正式包含Pa(VI)。PaO₂²⁺的碰撞诱导解离表明了镤酰的连接方式为{O-Pa-O}²⁺。实验测定的IE[PaO₂⁺]约为16.6 eV，与PaO₂⁺和PaO₂²⁺的自洽场和组态相互作用计算结果一致。这些计算为这些离子的电子结构提供了见解，并表明在镤酰的情况下5f轨道参与成键且存在部分“6p空穴”。发现PaO₂²⁺催化N₂O氧化CO，这种通过双正价金属氧化物离子的氧原子转移是独特的。还观察到PaO₂²⁺能够活化H₂形成稳定的PaO₂H₂⁺离子。
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