Synthesis, Characterization, and Reactivity of a Uranyl β-Diketiminate Complex

Addition of 1 equiv of Li(Ar2nacnac) (Ar2nacnac = (2,6-iPr2C6H3)NC(Me)CHC(Me)N(2,6-iPr2C6H3))
to an Et2O suspension of UO2Cl2(THF)3 generates the uranyl dimer [UO2(Ar2nacnac)Cl]2 (1) in good yield.
A second species can be isolated in low yield from the reaction mixtures of 1, namely [Li(OEt2)2][UO2(Ar2nacnac)Cl2] (2). The structures of both 1 and 2 have been confirmed by X-ray crystallography. Complex 1
reacts with Ph3PO to generate UO2(Ar2nacnac)Cl(Ph3PO) (3). In addition, 1 reacts with AgOTf and either
1 equiv of DPPMO2 or 2 equiv of Ph2MePO to provide [UO2(Ar2nacnac)(DPPMO2)][OTf] (4) and [UO2(Ar2nacnac)(Ph2MePO)2][OTf] (5), respectively. Both 4 and 5 have been fully characterized, including analysis
by X-ray crystallography and cyclic voltammetry. Reduction of 4 with Cp2Co provides UO2(Ar2nacnac)(CH{Ph2PO}2) (6), a uranyl(VI) complex that is generated by the formal loss of H• from the DPPMO2 ligand.
Labeling studies have been performed in an attempt to elucidate the mechanism of hydrogen loss. In
contrast, reduction of 5 with Cp2Co provides UO2(Ar2nacnac)(Ph2MePO)2 (7), a rare example of a uranyl(V) complex. As expected, the solid-state molecular structure of 7 reveals slightly longer U−O(oxo) bond
lengths relative to 5. Furthermore, complex 7 can be converted back into 5 by oxidation with AgOTf in
toluene.

向 Et2O 悬浮液中加入 1 等价的 Li(Ar2nacnac)（其中 Ar2nacnac = (2,6-iPr2C6H3)NC(Me)CHC(Me)N(2,6-iPr2C6H3)），可生成高收率的铀酰二聚体 [UO2(Ar2nacnac)Cl]2（1）。从 1 的反应混合物中可低收率地分离出第二种化合物，即 [Li(OEt2)2][UO2(Ar2nacnac)Cl2]（2）。通过 X 射线晶体学已证实 1 和 2 的结构。复合物 1 与 Ph3PO 反应生成 UO2(Ar2nacnac)Cl(Ph3PO)（3）。此外，1 与 AgOTf 及 1 等份的 DPPMO2 或 2 等份的 Ph2MePO 反应，分别提供 [UO2(Ar2nacnac)(DPPMO2)][OTf]（4）和 [UO2(Ar2nacnac)(Ph2MePO)2][OTf]（5）。4 和 5 已经过全面表征，包括 X 射线晶体学和循环伏安法分析。4 与 Cp2Co 的还原反应产生 UO2(Ar2nacnac)(CH{Ph2PO}2)（6），这是一种通过 DPPMO2 配体的形式氢原子损失生成的铀酰(VI)配合物。为了阐明氢原子损失机制，进行了标记研究。相反，5 与 Cp2Co 的还原反应产生 UO2(Ar2nacnac)(Ph2MePO)2（7），这是一个罕见的铀酰(V)配合物例子。正如预期，7 的固态分子结构相对于 5 显示出略长的 U−O(oxo) 键长。此外，通过在甲苯中用 AgOTf 氧化，7 可逆地转化为 5。