一系列偶氮苯及其不对称取代衍生物的双环钯配合物,其中{LPdCl(mu-AZB)LPdCl},其中AZB为偶氮苯,4-甲基偶氮苯,4-氨基偶氮苯或4-(二甲基氨基)-4'-硝基偶氮苯L是N,N-二甲基甲酰胺,二甲基亚砜或吡啶。通过X射线衍射分析以及(1)1 H NMR,IR,UV-vis和荧光分析确定了它们的结构和光谱性质。通过量子化学计算合理化了实验结果。已经解决了几种配合物的晶体结构,并且首次证明环钯可发生在对位具有强吸电子取代基的偶氮苯芳环上。在所有情况下,金属碳和氮 N-二甲基甲酰胺或二甲基亚砜配体是相互反式的,而吡啶配体是顺式的。通过比较计算出的异构体结构能,可以解释分离出的化合物中的顺/反异构现象。所有的配合物在可见光区域都具有很强的吸收能力,根据随时间变化的密度泛函理论计算,大部分吸收可归因于配体内pi-> pi *或金属到配体的电荷转移跃迁。观察到与4-氨基偶氮苯或4-(二
Solid-state reactions of dicyclopalladated azobenzenes and triphenylphosphine lead to the thermodynamically favorable bridged complexes. It was demonstrated for the first time that very complex molecular dynamics involving a series of structural transformations is also feasible in the solid state.
Two series of new dicyclopalladated complexes (DMF)PdCl(mu-(RC6H3N)-C-1=NC6H3R2)PdCl(DMF)} of 4,4'-functionalized azobenzenes with substituents of varying electron-donating or electron-withdrawing strength (R-1 = H, NMe2; R-2 = H, Cl, Br, I, OMe, PhNH, CO2H, SO3Na, or NO2) have been synthesized and fully characterized. H-1 NMR spectroscopy along with the ESI mass spectrometry unambiguously identified the new complexes in the solution, and their solid-state structures were determined by X-ray crystallography. The presence of easily exchangeable solvent ligands was confirmed by H-1 NMR spectroscopy, X-ray experiments, and ESI mass spectrometry. The complexes were additionally characterized by UV-vis and fluorescence spectroscopies. The effect of different 4,4'-substituents on the formation rate of mono- and dicyclopalladated azobenzenes was studied by UV-vis spectroscopy. The experimental results are complemented by the quantum-chemical (DFT) calculations in order to rationalize the kinetic results as well as substituent effects on the reaction rates. It was found that the mono- and dicyclopalladation reactions of azobenzenes proceed in two consecutive processes, adduct formation and palladation steps. The rate-determining step in both palladations is the breaking of the ortho C-H bond, which has been confirmed as an electrophilic substitution process by Hammett correlations and DFT calculations.