Department of Laboratory Methods and Medical Technology, Faculty of Health and Social Studies, University of South Bohemia, J. Boreckého 27, 370 11 České Budějovice, Czech Republic.
J Chem Phys. 2011 Jan 14;134(2):024520. doi: 10.1063/1.3515534.
The hydration process for two Ru(II) representative half-sandwich complexes: Ru(arene)(pta)Cl(2) (from the RAPTA family) and Ru(arene)(en)Cl (further labeled as Ru_en) were compared with analogous reaction of cisplatin. In the study, quantum chemical methods were employed. All the complexes were optimized at the B3LYP/6-31G(d) level using Conductor Polarizable Continuum Model (CPCM) solvent continuum model and single-point (SP) energy calculations and determination of electronic properties were performed at the B3LYP∕6-311++G(2df,2pd)/CPCM level. It was found that the hydration model works fairly well for the replacement of the first chloride by water where an acceptable agreement for both Gibbs free energies and rate constants was obtained. However, in the second hydration step worse agreement of the experimental and calculated values was achieved. In agreement with experimental values, the rate constants for the first step can be ordered as RAPTA-B > Ru_en > cisplatin. The rate constants correlate well with binding energies (BEs) of the Pt∕Ru-Cl bond in the reactant complexes. Substitution reactions on Ru_en and cisplatin complexes proceed only via pseudoassociative (associative interchange) mechanism. On the other hand in the case of RAPTA there is also possible a competitive dissociation mechanism with metastable pentacoordinated intermediate. The first hydration step is slightly endothermic for all three complexes by 3-5 kcal∕mol. Estimated BEs confirm that the benzene ligand is relatively weakly bonded assuming the fact that it occupies three coordination positions of the Ru(II) cation.
两种 Ru(II) 代表性半夹心配合物的水合过程进行了比较：Ru(arene)(pta)Cl(2)（来自 RAPTA 家族）和 Ru(arene)(en)Cl（进一步标记为 Ru_en），并与顺铂的类似反应进行了比较。在这项研究中，采用了量子化学方法。所有配合物均在 B3LYP/6-31G(d)水平下进行优化，采用导体极化连续体模型（CPCM）溶剂连续体模型，并在 B3LYP∕6-311++G(2df,2pd)/CPCM 水平下进行单点（SP）能量计算和电子性质的测定。结果表明，水合模型在取代第一个氯离子时效果相当好，得到了吉布斯自由能和速率常数的可接受的一致性。然而，在第二步水合中，实验和计算值的一致性较差。与实验值一致，第一步的速率常数可以按照 RAPTA-B > Ru_en > 顺铂的顺序排列。速率常数与反应物配合物中 Pt∕Ru-Cl 键的结合能（BEs）很好地相关。Ru_en 和顺铂配合物上的取代反应仅通过拟协同（协同交换）机制进行。另一方面，在 RAPTA 的情况下，也可能存在具有亚稳五配位中间体的竞争性离解机制。对于所有三种配合物，第一步水合都是略微吸热的，吸热约 3-5 kcal∕mol。估计的 BEs 证实了苯配体的结合较弱，因为它占据了 Ru(II)阳离子的三个配位位置。
