Solvent and temperature induced switching between structural isomers of Rh(I) phosphinoalkyl thioether (PS) complexes.
Solvent and temperature induced switching between structural isomers of Rh(I) phosphinoalkyl thioether (PS) complexes.
复制标题
溶剂和温度诱导 Rh(I) 膦烷基硫醚 (PS) 配合物结构异构体之间的转换。
DOI：
10.1021/ic101021t
复制
发表时间：
2010
影响因子：
4.6
通讯作者：
Mirkin,ChadA
中科院分区：
文献类型：
--
作者：
Wiester,MichaelJ;Braunschweig,AdamB;Yoo,Hyojong;Mirkin,ChadA
为了开发基于弱链方法（WLA）的功能体系，了解溶剂和配体结合强度如何改变由该方法形成的配合物的配位几何是很重要的。合成了一系列具有不同给电子能力的磷酸烷基硫醚（PS）半可溶配体，并将其掺入均寡化RhI(PS)2Cl配合物中，以了解溶剂和配体结合强度对首选配位模式的影响。在不同的ch2cl2和四氢呋喃（THF）溶剂混合物中，采用变温31p核磁共振光谱研究了这些RhI(PS)2Cl配合物在封闭和半开放结构异构体之间的转换，得到了热力学参数（ΔG°，ΔH°，TΔS°和keq）。同分异构体中氯离子的位置不同。在封闭异构体中，Cl -阴离子占据了外配位球，而在半开放异构体中，Cl -阴离子移动了内配位球并移动了一个Rh - S键。封闭异构体在ch2cl2中有利，半开放异构体在THF中有利。根据etn溶剂极性标度，在15种不同的溶剂中确定了平衡时对任何异构体的偏好，更倾向于封闭异构体的极性溶剂。对异构体的偏好还取决于与PS配体的硫相连的基团的给电子能力，给电子基团倾向于封闭异构体，而吸电子基团倾向于半开放异构体。在所研究的所有条件下，从封闭异构体形成半开放异构体在熵上是有利的，而在焓上是不利的。阐明决定两种异构体之间平衡的原理和环境将有助于设计由WLA制备的功能配合物。
To develop functional systems based on the weak-link approach (WLA), it is important to understand how solvent and ligand binding strength alter the coordination geometry of complexes formed from this method. A series of phosphinoalkyl thioether (PS) hemilabile ligands with varying electron donating abilities were synthesized and incorporated into homoligated RhI(PS)2Cl complexes to help understand the effects of solvent and ligand binding strength on the preferred coordination modes. The switching between closed and semiopen structural isomers of these RhI(PS)2Cl complexes was studied by variable temperature31P NMR spectroscopy in different solvent mixtures of CH2Cl2and tetrahydrofuran (THF) to obtain thermodynamic parameters (ΔG°, ΔH°,TΔS°, andKeq). The isomers differ in the position of the chloride counterion. In the closed isomer, the Cl−anion occupies the outer coordination sphere, while in the semiopen isomer, the Cl−has moved inner sphere and displaced one of the Rh−S bonds. The closed isomer is favored in CH2Cl2and the semiopen isomer is favored in THF. The preference for either isomer at equilibrium depends on the solvent polarity, based upon theETNsolvent polarity scale, as was determined from 15 different solvents, with more polar solvents favoring the closed isomer. The isomer preference also depends on the electron donating ability of the group attached to the sulfur of the PS ligand, with electron donating groups favoring the closed isomers and electron withdrawing groups favoring the semiopen isomers. The formation of the semiopen isomer from the closed isomer is entropically favored but enthalpically disfavored under all conditions studied. Elucidation of the principles and environments that determine the equilibrium between the two isomers will aid in the design of functional complexes prepared by the WLA.