- Design, synthesis and properties of orthopalladated complexes: Proheterogeneous catalyst
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The reaction of multidentate ligand, 3-((E)-(2-((E)-4-aryldiazenyl)phenylimino)methyl)benzene-1,2-diol, H2L (H2L1, 1a; H2L2, 1b and H2L3, 1c) and (E)-2-((2-(aryldiazenyl)phenylamino)methyl)phenol, HA (HA1, 3a; HA2, 3b and HA3, 3c) [where H represents the dissociable protons upon complexation, and aryl groups of H2L and HA are phenyl for H2L1 and HA1, p-methylphenyl for H2L2 and HA2, and p-chlorophenyl for H2L3 and HA3], with Na2PdCl4 separately afforded orthometallated complexes [(L)Pd], (2a, 2b and 2c) and [(A)PdCl] (4a, 4b and 4c) respectively. In the case of [(L)Pd], the deprotonated L2- ligands bind palladium (II) in a tetradentate (C,N,N,O) fashion whereas in the case of [(A)PdCl], the deprotonated A- ligands bind Pd(II) in tridentate (C,N,N) manner. X-ray structures of [(L1)Pd], (2a) and [(A1)PdCl] (4a) were determined to confirm the molecular structures. Both the complexes 4a and 5a exhibited catalytic activity toward Suzuki and Heck reactions. Conversion of [(A)PdCl] to its oxidized form upon ligand oxidation is reported.
- Das, Uttam,Pattanayak, Poulami,Patra, Debprasad,Brand?o, Paula,Felix, Vitor,Chattopadhyay, Surajit
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- Mesoporous silica nanospheres supported atomically precise palladium nanocluster: Highly efficient and recyclable catalysts in the reduction of 4-nitrophenol and Heck reactions
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Atomically precise palladium nanoclusters show great potential applications in the field of catalysis owing to its ultrasmall size and precise structure. This work, we report the mesoporous silica nanoparticles (MSNs) supported [Pd3Cl(PPh3)3(PPh2)2]Cl catalysts (denoted as Pd3Cl/MSNs) for the reduction of 4-nitrophenol and Heck coupling reactions of iodobenzene and styrenes. High uniform MSNs, with average diameter ≈110 nm, were prepared by sol–gel method, followed by Pd nanoclusters immobilization into the pore of MSNs. The MSNs supported Pd nanoclusters were well characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR), and diffuse reflectance optical spectrum. The results indicated that Pd3Cl nanoclusters after immobilized into the pores of MSNs are intact and possess good dispersibility. The catalytic performance of as-prepared nanocomposites was evaluated by the reduction of 4-nitrophenol and Heck reactions. The 4-nitrophenol could be completely conversion to 4-aminophenol within 6?min. Meanwhile, the as-prepared Pd3Cl/MSNs exhibit excellent catalytic performance in the Heck reactions between iodobenzenes and styrenes. The high catalytic activity of Pd3Cl/MSNs could be attributed to the large surface area and unique geometric structure of as-prepared Pd nanoclusters. More importantly, the catalysts could be easily recycled by centrifugation and shows excellent reusability.
- Gao, Taiping,Kang, Zhenlu,Zhao, Yining,Zhou, Yilin
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- Azo-amide palladium(II) complexes: Synthesis, characterization and application in C–C cross-coupling reactions
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The newly designed tridentate ligands bis-2,2′-(N-alkylamino)azobenzene, 1a-1d, have been prepared by the reaction between 2,2′-diaminoazobenzene and alkyl halides in the presence of K2CO3. These ligands were reacted with Na2[PdCl4] in a 1:1 ratio in methanol to give the new Pd(II) complexes 2a–2d. All the compounds were characterized by 1H NMR, IR spectroscopy and elemental analysis. Furthermore, the solid-state structures of the ligand 1a and two complexes (2a and 2c) were determined using single crystal X-ray diffraction analysis. The diffraction analysis revealed that the ligands bind with the Pd(II) ion in a monoanionic tridentate (N,N,N) fashion, offering a distorted square planar geometry where the fourth position is occupied by one chloride ligand. The air/moisture stable complex 2a was employed as an efficient catalyst for the Suzuki and Heck reactions under mild conditions. The catalyst exhibits high catalytic activities for the coupling of several aryl halides with phenyl boronic acid and styrene, providing excellent yields. Further, the catalyst can be easily recovered by simple chromatographic separation and reused up to three times without significant loss of its catalytic activity.
- Pratihar, Jahar Lal,Mandal, Paritosh,Lin, Chia-Her,Lai,Mal, Dasarath
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p. 224 - 230
(2017/08/08)
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- Unlocking Mizoroki–Heck-Type Reactions of Aryl Cyanides Using Transfer Hydrocyanation as a Turnover-Enabling Step
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A new transfer hydrofunctionalization strategy to turnover H-MII-X complexes has enabled both intra- and intermolecular Mizoroki–Heck (MH)-type reactions of aryl cyanides that are challenging to realize under traditional, basic conditions. Initially, a cascade carbonickelation/MH reaction of 2-cyanostyrenes was achieved using a key alkyne transfer hydrocyanation step. Mechanistic experiments supported the proposed catalytic cycle, including the turnover-enabling transfer hydrocyanation step. The reactivity was then extended to the intermolecular MH reaction of benzonitriles and styrenes.
- Fang, Xianjie,Yu, Peng,Prina Cerai, Gabriele,Morandi, Bill
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supporting information
p. 15629 - 15633
(2016/10/24)
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- Synthesis of a cyclometalated 1,3,5-triphenylpyrazole palladium dimer and its activity towards cross coupling reactions
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A phosphine free 1,3,5-triphenylpyrazole acetate-bridged palladacycle was prepared from simple commercially available starting materials. The activity of the palladacycle in the Mizoroki-Heck and Suzuki-Miyaura cross-coupling reactions was evaluated. The palladacycle precatalyst shows a wide substrate scope, both in Mizoroki-Heck as well as in Suzuki-Miyaura cross-coupling reactions using low catalyst loadings viz., 0.2 mol% and 0.1 mol% respectively.
- Mamidala, Ramesh,Mukundam, Vanga,Dhanunjayarao, Kunchala,Venkatasubbaiah, Krishnan
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p. 5805 - 5809
(2015/03/30)
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- Ruthenium and palladium complexes incorporating amino-azo-phenol ligands: Synthesis, characterization, structure and reactivity
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The ligands 2-((2-aminophenyl)diazenyl)phenol, HOL1-NH2, 1a; 2-((2-aminophenyl)diazenyl)-5-methylphenol, HOL2-NH2, 1b; and 2-((2-aminophenyl) diazenyl)-5-chlorophenol, HOL3-NH2, 1c, which are abbreviated as HOL-NH2, 1, afforded the complexes of compositions [(OL-NH)Pd(PPh3)], 2, and [(OL-NH)Ru(CO)(PPh3)2], 3, upon reaction with Na2PdCl4 and Ru(CO)3(PPh3)3 respectively. In all the complexes the metals ions, Pd(II) or Ru(II), are coordinated by deprotonated ligand (OL-NH)2- in tridentate (N, N, O) fashion. X-ray structures of [(OL2-NH)Pd(PPh3)], 2b, and [(OL1-NH)Ru(CO)(PPh3)2], 3a, were determined to confirm the molecular structures. The cyclic voltammograms of [(OL-NH)Ru(CO)(PPh3)2] exhibited two quasi reversible oxidative response near 0.25 and 1.12 V vs. SCE. The nature of HOMO as obtained by DFT calculations has been inspected to have an insight into the redox orbitals. The newly synthesized [(OL-NH)Pd(PPh3)], 2a, complexes exhibited catalytic activity toward the Suzuki, Heck, Cyanation and amination reactions. Catalytic activity of complex [(OL1-NH)Ru(CO)(PPh3)2], 3a, was examined for the conversion of ketones to corresponding alcohols by transfer hydrogen reactions.
- Pattanayak, Poulami,Parua, Sankar Prasad,Patra, Debprasad,Lai,Brand?o, Paula,Felix, Vitor,Chattopadhyay, Surajit
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p. 122 - 131
(2015/03/04)
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- Synthesis, characterization, structure and properties of copper and palladium complexes incorporating azo-amide ligands
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The reaction of the multidentate ligand N-(2-(aryldiazenyl)phenyl) picolinamide, HL (3a, 3b and 3c) [HL is ArN = NC6H 4NHC(O)Py, where Ar is C6H5 for HL1 (3a), p-MeC6H4 for HL2 (3b) or p-ClC 6H4 for HL3 (3c), and Py stands for pyridyl], with Cu(CH3COO)2·H2O and Na 2PdCl4 separately afforded the complexes [(L) 2Cu] (4a, 4b and 4c) and [(L)PdCl] (5a, 5b and 5c) respectively, where the deprotonated ligand L- binds copper(II) and palladium(II) in a tridentate (N,N,N) fashion. X-ray structures of [(L3) 2Cu] (4c) and [(L1)PdCl] (5a) were determined to confirm the molecular structures. The newly synthesized complex 4a exhibits catalytic activity toward the oxidation of alcohols to the corresponding carbonyl compounds and oxidation of organic thioethers to sulfoxide and sulfone, whereas the complex 5a is an active catalyst for Suzuki and Heck reactions.
- Pattanayak, Poulami,Pratihar, Jahar Lal,Patra, Debprasad,Brand?o, Paula,Felix, Vitor,Chattopadhyay, Surajit
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- Synthesis, characterization, structure, redox property, antibacterial and catalytic activity of tridentate Schiff base cobalt(III), nickel(II) and palladium(II) complexes
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Ligand, HL, 2-((2-(benzylthio)phenylimino)methyl)phenol, upon reaction with Co(NO3)3·6H2O, Ni(OAc) 2·4H2O and PdCl2 separately afforded complexes [(L)2Co]NO3 (1), [(L)2Ni] (2) and [(L)PdCl] (3) respectively. The new complexes were characterized by usual spectroscopic studies like UV-Vis, IR and NMR and authenticated by X-ray structure determination on [(L)2Co]NO3, [(L) 2Ni]. The analysis of crystal structures revealed that in all the complexes the ligand HL binds the metal center as uni-negative anion; L - dissociating phenolic proton and offers (O, N, S) tridentate binding mode to the metal. The compound [Co(L)2]NO3 is tested for in vitro antibacterial activity. Complex 3, acts as a catalyst in Heck reaction for a number of substrates. Complexes 1 and 2 exhibited a quasi reversible oxidative responses at 0.97 and 0.85 V, respectively, versus SCE. The electronic spectra and redox properties of the complexes have been explained with DFT computation.
- Pattanayak, Poulami,Pratihar, Jahar Lal,Patra, Debprasad,Lin, Chia-Her,Paul, Sobhana,Chakraborty, Kausiki
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p. 275 - 282
(2013/04/23)
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- Tetranuclear assembly of palladium(II): Catalyst for C-C coupling reactions
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The 2-((2-benzylamino)phenyldiazenyl)phenol, H2OL [where H 2OL = ArOHN = NC6H4N(H)CH2(C 6H5); Ar = C6H5 (for H2OL1), p-MeC6H4 (for H2OL2) or p-ClC 6H4 (for H2OL3)], ligands were prepared by the reaction of the appropriate 2-((2-hydroxyaryl)azo)anilines with benzyl bromide. The reactions of Na2PdCl4 with H 2OL afforded tetranuclear Pd(II) complexes of the composition [Pd(OL)]4. The ligands bind palladium(II) in a tridentate (N, N, O) fashion. The X-ray structure of [Pd(OL1)]4 was determined to confirm the characterization. The newly synthesized [Pd(OL1)] 4 complex was utilized as a catalyst for the Suzuki and Heck reaction for a variety of substrates.
- Pattanayak, Poulami,Pratihar, Jahar Lal,Patra, Debprasad,Lin, Chia-Her,Chattopadhyay, Surajit
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p. 133 - 138
(2013/10/22)
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- Synthesis, characterization and structure of new diazoketiminato chelates of palladium(II): Potential catalyst for C-C coupling reactions
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The 1N-(N,N-diethylaminoethyl)-2-arylazoaniline, HL [where HL = ArN = NC6H4N(H){C2H4N(C2H 5)2}; Ar = C6H5 (for HL 1), p-MeC6H4 (for HL2) or p-ClC 6H4 (for HL3)], ligands were prepared by treating the appropriate 2-(arylazo)aniline with 2-bromo-N,N-diethylethanamine. Reactions of Na2PdCl4 with HL afforded the [(L)PdCl] complexes. HL binds palladium(II) in a tridentate fashion (N,N,N), forming a new diazoketiminato chelate. The X-ray structure of [(L3)PdCl] was determined to confirm the characterization. The newly synthesized complex [(L1)PdCl] was utilized to carry out Suzuki and Heck reactions for a variety of substrates.
- Pratihar, Jahar Lal,Pattanayak, Poulami,Patra, Debprasad,Lin, Chia-Her,Chattopadhyay, Surajit
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experimental part
p. 67 - 73
(2012/03/09)
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- Organostannoxane-supported Pd(0) nanoparticles as efficient catalysts for Heck-coupling reactions
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A new functional organostannoxane cage, SnP, that contains phosphine ligands in its periphery has been structurally utilized as support palladium(0) nanoparticles SnPPd. The latter was shown to catalyze the Heck coupling reactions of wide variety of functionalities efficiently.
- Chandrasekhar, Vadapalli,Narayanan, Ramakirushnan Suriya
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supporting information; experimental part
p. 3527 - 3531
(2011/06/27)
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- Substituent Effect Studies of Aryl-Assisted Solvolyses. II. The Acetolysis of 2-Phenyl-2-(substituted phenyl)ethyl p-Toluenesulfonates
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The substituent effect on the acetolysis of 2-phenyl-2-(substituted phenyl)ethyl p-toluenesulfonates had a nonlinear LArSR correlation and was explicable in terms of a competitive aryl-assisted mechanism involving the X-substituted phenyl-assisted (kXM) pathway and the unsubstituted phenyl-assisted (kXN) pathway. By the application of the iterative nonlinear least-squares method based on the LArSR Eq., the substituent effect on the overall kt was dissected into the best-fit kM correlation of ρM=-3.53 with rM=0.60, and the kN correlation of ρN=-0.88 with ?0. The ρM and rM values for the effects of assisting aryl substituents are quite close to those of the 2-methyl-2-phenylpropyl system and the small ρN value with unexalted ?0 constant for the unassisting aryls is compatible to the remote β-aryl effect. The relative rates of competing pathways dissected based on the substituent effect analysis agreed completely with the ratio of respective aryl migration products determined by the 13C-tracer method. Exact rate-product correlation demonstrates that this system involves two discrete aryl-assisted pathways, kXM and kXN, which do not cross over.
- Fujio, Mizue,Maeda, Yasuyuki,Goto, Mutsuo,Saeki, Yoshihiro,Mishima, Masaaki,Tsuno, Yuho
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p. 3021 - 3029
(2007/10/02)
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