A planar binuclear tetrabenzoporphyrin and its dicopper derivative
A planar binuclear tetrabenzoporphyrin and its dicopper derivative
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平面双核四苯并卟啉及其二铜衍生物
DOI：
10.1021/ic00009a056
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发表时间：
1991
影响因子：
4.6
通讯作者：
T. Osa
中科院分区：
文献类型：
--
作者：
N. Kobayashi;Masaharu. Numao;R. Kondo;S. Nakajima;T. Osa
阿氏图（图3）给出11 = 82（±11）kJ mol-1和5*= 50（±30）J mol-1 K-1。活化熵的正值与我们提出的碳酸根配体从U_（02）（CO_3）~（34）′络合物中解离是速率决定步骤（方程式3）相一致。这个建议似乎是合理的，因为配合物是配位饱和的（三个碳酸根配体在赤道平面中与垂直于平面的铀酰氧双齿结合到U 022+离子17）（参见。见图4）。在固态下，U_（02）（C_（03））_（34'）的内配位层中不存在水。17在水溶液中，在结构相关的络合物（U 02）3（CO 3）66'中似乎也没有任何水与铀酰配位。因此，络合物U 02（C 03）34'在溶液中被水合的可能性似乎较小。因此，二级反应的可能性较小。显然，水分子可以参与交换反应（3）。然而，U 02（H2O）52+的水交换相对较快，k= 7.6 × 105 s-1.18。此外，负离子与金属离子的配位削弱并使金属-水键不稳定。18，19得出结论，即使发生水与铀酰络合物U 02（CO 3）34'或U 02（CO 3）22'的配位，水的缔合或解离也不会是反应3的速率决定步骤。Tomiyasu和Fukutomi 20回顾了一些涉及铀的配体交换反应。对于这些反应，大多数D或Id机制是针对单齿配体提出的，但对于更复杂的双齿或混合配体配合物体系尚未得出结论。
The Arrhenius plot (Figure 3) gives//1= 82 (±11) kJ mol'1 and 5*= 50 (±30) J mol'1 K'1. The positive value of the activation entropy is in agreement with our proposal that the dissociation of the carbonate ligandfrom the U02 (C03) 34'com-plex is the rate-determining step (eq 3). This proposal seems reasonable, since the complex is coordinatively saturated (three carbonate ligands are bidentately bound to the U022+ ion in the equatorial plane with uranyl oxygens perpendicular to the plane17)(cf. Figure 4). There is no water in the inner coordination sphere of U02 (C03) 34'inthe solid state. 17 Neither does there seem to be any water coordinated to uranyl in the structurally related complex (U02) 3 (C03) 66'in aqueous solution. 6 Hence, it seems less probable that the complex U02 (C03) 34'is aquated in solution. Thus, a second-order reaction is less probable. Obviously, water molecules can take part in the exchange reaction (3). However, water exchange for U02 (H20) 52+ is relatively fast, k= 7.6 X 105 s' 1.18 In addition, coordination of negative ions to the metal ion weakens and labilizes the metal-water bond (s). 18, 19 Concluding, even if coordination of water to a uranyl complex, U02 (C03) 34'or U02 (C03) 22', occurs, an association or a dissociation of water will not be the rate-determining step for reaction 3. Tomiyasu and Fukutomi20 reviewed some ligand-exchange reactions involving uranium. For these reactions, mostly D or Id mechanisms were proposed for monodentate ligands, but no conclusion was reached for more complicated systems of bidentate or mixed-ligand complexes.