Miyamoto Naomi, Ikeda Yasuhisa, Tsukahara Takehiko
Laboratory for Advanced Nuclear Energy, Institute of Innovative Research, Tokyo Institute of Technology, 2-12-1-N1-6 Ookayama, Meguro-ku, Tokyo 152-8550, Japan.
Inorg Chem. 2020 Aug 17;59(16):11347-11356. doi: 10.1021/acs.inorgchem.0c00979. Epub 2020 Jul 30.
In order to examine the possibility of Lewis acid-Lewis base (LA-LB) interactions between the boron atom of B(CF)OH and the oxo groups ("yl" oxygen atoms) of uranyl β-diketonato complexes, we have measured the H, B, O, F NMR and IR spectra of toluene solutions containing β-diketonato complexes [UO(acac)DMSO or UO(dfh)DMSO, where acac = 2,4-pentanedionate, dfh = 1,1,1,2,2,6,6,7,7,7-decafluoroheptane-3,5-dionate, and DMSO = dimethyl sulfoxide] and B(CF)OH. B and O NMR spectra of solutions containing UO(dfh)DMSO and B(CF)OH showed no change in their chemical shifts regardless of the [B(CF)OH]/[UO(dfh)DMSO] ratio. This indicates that there were no apparent interactions between B(CF)OH and UO(dfh)DMSO. On the other hand, in the corresponding NMR spectra of solutions containing UO(acac)DMSO and B(CF)OH, new signals were observed at a higher field than signals observed in the solutions containing only B(CF)OH or UO(acac)DMSO, and their intensity changed with the [B(CF)OH]/[UO(acac)DMSO] ratio. These results reveal that a complex with LA-LB interaction (B···O═U) between the boron atom of B(CF)OH and the "yl" oxygen atom of UO(acac)DMSO was formed. IR spectra also supported such complex formation; i.e., the asymmetric O═U═O stretching band of UO(acac)DMSO was observed to shift from 897 to 810 cm with the addition of B(CF)OH. Moreover, F NMR spectra indicated that 1:1 and 2:1 LA-LB complexes exist in equilibrium, UO{OB(CF)OH}(acac)DMSO + B(CF)OH = U{OB(CF)OH}(acac)DMSO. The thermodynamic parameters for this equilibrium were obtained as = (2.5 ± 0.6) × 10 M (at 25 °C), Δ = -42.4 ± 5.2 kJ mol, and Δ = -96.7 ± 19.4 J K mol. In H NMR spectra, the signal due to -CH groups of UO(acac)DMSO disappeared, and three signals due to the corresponding -CH groups newly appeared with an increase in the [B(CF)OH]/[UO(acac)DMSO] ratio. From these phenomena, it is proposed that 1:1 and 2:1 LA-LB complexes having interactions between the -CH groups of acac and the -OH group of coordinated B(CF)OH are formed depending on the [B(CF)OH]/[UO(acac)DMSO] ratio.
为了研究B(CF)OH的硼原子与铀酰β - 二酮配合物的羰基氧原子（“酰基”氧原子）之间形成路易斯酸 - 路易斯碱（LA - LB）相互作用的可能性，我们测量了含有β - 二酮配合物[UO(acac)DMSO或UO(dfh)DMSO，其中acac = 2,4 - 戊二酮，dfh = 1,1,1,2,2,6,6,7,7,7 - 十氟庚烷 - 3,5 - 二酮，DMSO = 二甲基亚砜]和B(CF)OH的甲苯溶液的氢、硼、氧、氟核磁共振谱和红外光谱。含有UO(dfh)DMSO和B(CF)OH的溶液的硼和氧核磁共振谱显示，无论[B(CF)OH]/[UO(dfh)DMSO]的比例如何，其化学位移均无变化。这表明B(CF)OH与UO(dfh)DMSO之间没有明显的相互作用。另一方面，在含有UO(acac)DMSO和B(CF)OH的溶液的相应核磁共振谱中，在比仅含有B(CF)OH或UO(acac)DMSO的溶液中观察到的信号更高的场强处出现了新信号，并且它们的强度随[B(CF)OH]/[UO(acac)DMSO]的比例而变化。这些结果表明，在B(CF)OH的硼原子与UO(acac)DMSO的“酰基”氧原子之间形成了具有LA - LB相互作用（B···O═U）的配合物。红外光谱也支持这种配合物的形成；即，随着B(CF)OH的加入，UO(acac)DMSO的不对称O═U═O伸缩带从897 cm移动到810 cm。此外，氟核磁共振谱表明1:1和2:1的LA - LB配合物处于平衡状态，UO{OB(CF)OH}(acac)DMSO + B(CF)OH = U{OB(CF)OH}(acac)DMSO。该平衡的热力学参数为 = (2.5 ± 0.6) × 10 M（在25°C下），Δ = -42.4 ± 5.2 kJ mol，Δ = -96.7 ± 19.4 J K mol。在氢核磁共振谱中，UO(acac)DMSO的 - CH基团产生的信号消失，并且随着[B(CF)OH]/[UO(acac)DMSO]比例的增加，相应的 - CH基团产生的三个新信号出现。基于这些现象，有人提出，根据[B(CF)OH]/[UO(acac)DMSO]的比例，形成了在acac的 - CH基团与配位的B(CF)OH的 - OH基团之间具有相互作用的1:1和2:1的LA - LB配合物。
