Kinetico-mechanistic studies of C-H bond activation on new Pd complexes containing N,N'-chelating ligands.
Kinetico-mechanistic studies of C-H bond activation on new Pd complexes containing N,N'-chelating ligands.
复制标题
含有 N,N-螯合配体的新型 Pd 配合物上 C-H 键活化的动力学机制研究。
DOI：
10.1039/b415613g
复制
发表时间：
2005
影响因子：
4
通讯作者：
M. Font‐Bardia
中科院分区：
文献类型：
--
作者：
I. Favier;M. Gómez;J. Granell;Manuel A Martínez;X. Solans;M. Font‐Bardia
合成了不同构型的亚胺/胺钯（II）配合物[PdX_2（kappa_2-N（imino），N（amino））]（X = Cl，AcO; kappa_2-N（imino），N（amino）= 4ClC_6 H_4CHNCH_2（CH_2）_nN（CH_3）_2，n= 1，2）。测定了其中四个化合物E-1AcO、Z-1AcO、E-2AcO和E-2Cl的晶体结构，并研究了它们在常用环金属化溶剂乙酸中的溶液行为。乙酸溶液中的配合物被证明保持由X-射线晶体学确定的结构，因为它们在氘代氯仿。然而，通过NMR实验观察到{Pd（κ 2-N（亚氨基），N（氨基））}环的部分打开平衡。当配合物在溶液中保持较长时间时，得到相应的环化衍生物，1AcO-CM，2AcO-CM，1Cl-CM和2Cl-CM，其含有{Pd（k2-C，N（imino））}钯配体，如通过1H NMR光谱表征的。在这些化合物中，配体的N（氨基）部分的完全打开已经发生。在不同的温度、压力和酸浓度下，对C-H键活化过程进行了动力学-力学研究;结果与在适当的环化反应之前需要打开[PdX 2（kappa 2-N（亚氨基），N（氨基））]中的螯合环一致。的活化的doppies的值是高于那些观察到的已知的N-单齿环金属化配体，应该对应于配体脱螯预平衡的贡献。熵和激活量也表明了这种预解离，其中包括重要的收缩有序。少量的三氟甲磺酸在反应介质中的存在下，加速反应的N（亚氨基）-单齿系统中观察到的值，表明螯合环的完全开放已经发生。对于螯合络合物（Z）中配体的取向不良的异构体形式，环化过程甚至更慢，并且直接对应于配体重组成其环钯化活性（E）构象。
The hybrid imine/amine palladium(II) coordination complexes [PdX2(kappa2-N(imino),N(amino))](X = Cl, AcO; kappa2-N(imino),N(amino)= 4ClC6H4CHNCH2(CH2)nN(CH3)2, n= 1, 2) have been prepared in different isomeric forms which include E/Z arrangement around the C[double bond]N bond of the hybrid ligand and {Pd(kappa(2)-N(imino),N(amino))} ring conformation. The crystal structures of four of them, E-1AcO, Z-1AcO, E-2AcO and E-2Cl, have been determined and the solution behaviour in acetic acid, the common cyclometallating solvent, for all these systems studied. The complexes in acetic acid solution are shown to maintain the structure determined by X-ray crystallography, as they do in deuterated chloroform. Nevertheless, a partial opening equilibrium of the {Pd(kappa2-N(imino),N(amino))} ring is observed by NMR experiments. When the complexes are held in solution for longer periods the corresponding cyclometallated derivatives, 1AcO-CM, 2AcO-CM, 1Cl-CM and 2Cl-CM, containing the {Pd(kappa2-C,N(imino))} palladacycle are obtained, as characterized by 1H NMR spectroscopy. In these compounds the total opening of the N(amino) moiety of the ligand has occurred. The C-H bond activation process has been studied kinetico-mechanistically at different temperatures, pressures and acid concentrations; the results agree with the need of an opening of the chelate ring in [PdX2(kappa2-N(imino),N(amino))] prior to the proper cyclometallation reaction. The values of the enthalpies of activation are higher than those observed for known N-monodentated cyclometallating ligands, as should correspond to the contribution of a ligand dechelation pre-equilibrium. The entropies and volumes of activation are also indicative of this predissociation that include an important amount of contractive ordering. The presence of small amounts of triflic acid in the reaction medium accelerates the reaction to the value observed for N(imino)-monodentate systems, indicating that the full opening of the chelate ring has taken place. For the badly oriented isomeric forms of the ligand in the chelated complex (Z), the cyclometallation process is even more slow and corresponds directly to the reorganization of the ligand to its cyclopalladation-active (E) conformation.