2,4-bis(4-methoxyphenyl)-1,3,2,4-dithiadiphosphetane-2,4-disulfide (Lawesson's reagent) was made to react with benzylamine to produce [(PhCH2NH)(p-C6H4OMe)PS2] -[PhCH2NH3] + in a very facile manner. From the abovementioned product, two new complexes {Pd[(PhCH2NH)(p-C6H4OMe)PS2]2} (C1) and {Cu2(PPh3)2[(PhCH2NH)(p-C6H4OMe)PS2]2} (C2) were obtained in high yields whose molecular structures were ascertained by X-ray diffraction analysis, IR and NMR spectroscopy, and elemental analysis. The catalytic properties of both complexes were evaluated in the Heck reaction. High turnover numbers (TONs) and yields were observed for palladium catalyst and It was revealed that dicopper(I) complex by a distance of 2.84 Å between metal ions, bearing triphenylphosphine and dithiophosphorus ligands, can catalyze the Heck reaction. This is the first report of Cu(I) complex as catalyst in the Heck reaction. Natural bonding orbital (NBO) analysis for C1 indicated that natural charge on Pd atom is -0.07e and Pd atom has formed four sigma bonds with S atoms. Similarly, NBO analysis revealed no significant Cu…Cu interaction in dicopper complex C2.
The palladium-catalyzed Heck reaction is the most effective method for vinylation of unsaturated halides. Here, new thermally stable palladium(II) complexes {(4OMeÀPh) RPS 2 } 2 Pd [R = C 5 H 11 NH (1); R = CH 3 CH 2 NHCH 3 (2); R=OCH 3 (3)] were readily synthesized in a high yield by the reaction of PdCl 2 with dithiophosphorus ligands. The molecular structures of 1 and 2 were determined by means of X-ray diffraction analysis. The catalytic activity of all complexes was evaluated in Heck reaction. The results revealed that the complexes are highly active catalysts in coupling of aryl bromides with styrene. The Hammett plot of the competition experiments of various aryl bromides with styrene, catalyzed by the complexes, displayed very good linear correlation with a positive slope (1) within a range of 3.99-4.39 for 1-3. The absence of any decomposition signs together with negative Hg-poisoning tests indicated that the liberation of Pd(0) species in the catalytic cycle is unlikely. So, it was supposed that the palladium(II)-catalyzed Heck reaction might not proceed via classical Pd(0)/Pd(II) catalytic cycle. To find the most probable mechanism, density functional theory calculations were performed and the predicted data compared with the experimental results. Upon the obtained results, the Pd(II)/Pd(IV) catalytic cycle was proposed as the most plausible mechanism. The overall free energy profile showed that the first step of the mechanism (oxidative addition) with a free energy barrier of 33.8 kcal/mol involves the highest energy barrier and can be considered as the rate determining step of the mechanism.
A magnetic vanadium oxide nanoparticles supported on spinel copper ferrite (CuFe 2 O 4 -VO x ) are prepared, characterized, and examined for the peroxymonosulfate (PMS) activation to degrade Rhodamine B (RhB) in water solution. Interestingly, the results show that despite the inability of mixture of copper ferrite and vanadium oxides nanoparticles to the effective RhB decomposition, the prepared catalyst exhibits an excellent catalytic ability toward RhB oxidation. The influence of vital parameters, such as temperature, PMS concentration, catalyst loading, and initial pH are discussed comprehensively. The kinetic studies demonstrate that the pseudo-first-order model is well fitted for RhB degradation in CuFe 2 O 4 -VO x /PMS system and the activation energy is estimated at 19.60 kJ mol À1 . Furthermore, it is found out that the concentration of leached metal ions in solution is negligible and PMS activation is done mainly on the surface of the catalyst. A probable mechanism of PMS activation over RhB degradation is proposed based on the results of free radical quenching studies and X-ray photoelectron spectroscopy (XPS) analysis. Radical quenching experiments using various scavengers suggest SO 4•À as a main reactive species in the degradation.
Palladium nanoparticles supported on polyoxometalate as a solid carrier were successfully prepared and evaluated as a heterogeneous nanocatalyst for the Mizoroki‐Heck cross‐coupling reactions. This supported catalyst was characterized by a set of techniques, including XRD, chemical analysis (ICP‐OES), IR spectroscopy, TEM and FE‐SEM analyses. Poly (ethylene glycol) was employed as an environmentally friendly solvent for coupling reactions. The various fundamental reaction parameters that influence the efficiency of the reaction and yield of the desired reaction products were optimized. This catalytic system showed good activities and evolve a strategy for achieving five times catalyst and green solvent recyclability without appreciable loss of its activity, thus making this protocol eco‐friendly.
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