Thaler Florian, Hubbard Colin D., Heinemann Frank W., van Eldik Rudi, Schindler Siegfried, Fábián István, Dittler-Klingemann Andreas M., Hahn F. Ekkehardt, Orvig Chris
Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, British Columbia V6T 1Z1, Canada.
Inorg Chem. 1998 Aug 10;37(16):4022-4029. doi: 10.1021/ic971295t.
Spectroscopic, thermodynamic, and kinetic measurements have been made on aqueous solutions of copper(II) complexes of hexamethylated tren and trimethylated tren (one methylation per primary amine group of tren) with the objective of correlating the influence of geometry (trigonal bipyramidal, evident from UV/vis spectroscopy) and N-alkyl substitution in the ligand on these inherent properties. At 25.0 degrees C the protonation constants of Me(3)tren are not significantly different from those of tren and Me(6)tren, and the stability constant for the Cu(II) complex is of the same order of magnitude as that for the Cu(tren)(H(2)O) complex ion. The pK(a) for deprotonation of the coordinated water molecule of Cu(Me(3)tren)(H(2)O) is intermediate between the values for the complexes containing the unsubstituted and the fully substituted tren ligand. Substitution (pyridine for water) kinetics measurements employing stopped-flow and temperature-jump methods revealed different patterns of reactivity: pyridine replaces water in Cu(Me(3)tren)(H(2)O) with a second-order rate constant of (4.4 +/- 0.8) x 10(2) M(-)(1) s(-)(1) at 25.0 degrees C, whereas the corresponding process for Cu(Me(6)tren)(H(2)O) is relatively complex and is discussed in more detail. Substitution in the former complex ion is characterized in the forward and reverse directions, by DeltaH() = 60 +/- 8 and 51.9 +/- 0.9 kJ mol(-)(1), DeltaS() = 5 +/- 27 and -23 +/- 3 J mol(-)(1) K(-)(1), and DeltaV() = -8.7 +/- 4.6 and -6.2 +/- 1.1 cm(3) mol(-)(1), respectively. It is concluded that this reaction follows an I(a) mechanism, similar to that reported for the comparable reaction of Cu(tren)(H(2)O). An X-ray structural determination on a crystal of Cu(2)(Me(3)tren)(2)(CN)(3).2CH(3)CN demonstrated trigonal bipyramidal geometry about each copper(II) center. As has been found in comparable complexes of tren and Me(6)tren, the axial nitrogen to copper bond is shorter than the equatorial nitrogen-copper bonds, and the angle made by N(axial)-Cu-N(equatorial) is less than 90 degrees (84.6-85.4 degrees ), signifying that each copper ion lies below the plane of the equatorial nitrogen atoms.
已对六甲基化tren和三甲基化tren（tren的每个伯胺基团有一个甲基化）的铜（II）配合物的水溶液进行了光谱、热力学和动力学测量，目的是关联几何结构（从紫外/可见光谱明显看出为三角双锥）和配体中N-烷基取代对这些固有性质的影响。在25.0℃时，Me(3)tren的质子化常数与tren和Me(6)tren的质子化常数没有显著差异，并且Cu（II）配合物的稳定常数与[Cu(tren)(H₂O)]²⁺络合离子的稳定常数处于同一数量级。[Cu(Me(3)tren)(H₂O)]²⁺中配位水分子去质子化的pKₐ值介于含有未取代和完全取代tren配体的配合物的值之间。采用停流法和温度跳跃法进行的取代（吡啶取代水）动力学测量揭示了不同的反应模式：在25.0℃时，吡啶以(4.4±0.8)×10² M⁻¹ s⁻¹的二级速率常数取代[Cu(Me(3)tren)(H₂O)]²⁺中的水，而[Cu(Me(6)tren)(H₂O)]²⁺的相应过程相对复杂，将进行更详细的讨论。前一种络合离子中的取代在正向和反向的特征分别为：ΔH⦵ = 60±8和51.9±0.9 kJ mol⁻¹，ΔS⦵ = 5±27和 -23±3 J mol⁻¹ K⁻¹，以及ΔV⦵ = -8.7±4.6和 -6.2±1.1 cm³ mol⁻¹。得出的结论是，该反应遵循I(a)机制，类似于报道的[Cu(tren)(H₂O)]²⁺的类似反应。对Cu₂(Me(3)tren)₂(CN)₃·2CH₃CN晶体的X射线结构测定表明，每个铜（II）中心周围为三角双锥几何结构。正如在tren和Me(6)tren的类似配合物中所发现的那样，轴向氮与铜的键长比赤道面氮 - 铜键短，并且N(轴向)-Cu-N(赤道)形成的角度小于90°（84.6 - 85.4°），这表明每个铜离子位于赤道面氮原子平面下方。
