Catalytic properties of several supported Pd(II) complexes for Suzuki coupling reactions

Pd(II) complexes with N-ligands were synthesized and tested for Suzuki coupling reaction. These complexes were also heterogenized on silica. The resulting site-isolated catalysts showed a high catalytic activity. The most stable complex was supported N-(propyl)ethylenediamine, which did not display any notable leaching. The effects of reaction conditions and the nature of the boronic acid derivative on the conversion of the starting compounds were studied.     

Effective binuclear Pd(II) complexes for Suzuki reactions in water

A series of new ionic binuclear Pd(II) complexes supported by water‐soluble bis(α‐diimine) ligands were prepared and employed as catalysts for the palladium‐catalyzed Suzuki reaction in aqueous media. The binuclear nature of the complexes increased the reaction rate, while electronic and steric modification of the ligand frameworks had a remarkable influence upon the catalytic activity of the palladium complexes. The catalysts were shown to be homogeneous through mercury poisoning experiments and complexes could be recycled more than 10 times without loss of catalytic activity. Copyright © 2013 John Wiley & Sons, Ltd.     

Palladium(II) thiocarboxamide complexes: synthesis, characterisation and application to catalytic Suzuki coupling reactions

A simple route to synthesise palladium(II) complexes from the reaction of N-substituted pyridine-2-thiocarboxamide ligands and PdCl(2)(PPh(3))(2) has been developed. The new complexes are very soluble in common solvents and have been fully characterised (elemental analysis, FT-IR, (1)H, (31)P, (13)C-NMR), including an X-ray diffraction analysis. The molecular structures of all the complexes were determined and reveal the presence of square planar geometry around Pd with little distortion. The complexes were tested in the Suzuki coupling of electronically deactivated aryl and heteroaryl bromides and were found to have much greater activity, without using any promoting additives or phase transfer agent under aerobic conditions. Higher reaction rates are obtained by varying R substituents on the aromatic ring of pyridine-2-thiocarboxamide. The effect of other variables on the cross-coupling reaction, such as temperature, solvent and base, is also reported.     

Synthesis of Pd(II) 1-alkylperimidine complexes as efficient catalysts for Suzuki reactions involving arylchlorides

Three palladium(II) complexes of the type [PdCl₂(PPh₃)L] (L—1-alkylperimidine) have been prepared by reactions of [PdCl₂(PPh₃)]₂ with 1-alkylperimidine. The complexes were characterized by conventional spectroscopic methods and elemental analyses. The incorporation of N-coordinated perimidine complexes of palladium(II) gave high catalytic activity in the Suzuki coupling deactivated aryl chloride substrates.From Koordinatsionnaya Khimiya, Vol. 31, No. 2, 2005, pp. 153–156. Original English Text Copyright © 2005 by Özdemir, Alýcý, Gürbüz, B. Çetinkaya, E. Çetinkaya.This article was submitted by the authors in English.     

Preparation of Pd(II) enolate complexes and their reactions

Palladium(II) enolate complexes have been prepared by the reaction of Pd(II)Cl₂-(PhCN)₂ with trimethylsilyl enol ethers and reacted with CO and ethylene.     

Microwave-assisted aqueous Suzuki coupling reactions catalyzed by ionic palladium(II) complexes

Suzuki coupling is one of the most powerful methods for the synthesis of biaryls. We have prepared and characterized a series of unsymmetrical sulfonated water-soluble Pd(II)-pyridyl imine complexes and investigated them as catalysts for the Suzuki cross-coupling reaction in water under microwave irradiation. The compounds proved to be effective catalysts.     

Synthesis and structural characterization of palladium(II) 2-(arylazo)naphtholate complexes and their catalytic activity in Suzuki and Sonogashira coupling reactions

Abstract

A family of five palladium(II) 2-(arylazo)naphtholate complexes, [PdCl(PPh₃)(L)] (L?=?O, N-donor of bidentate 2-(arylazo)naphtholate ligands), have been synthesized and characterized by elemental analysis and spectral (FT-IR, UV–Vis, ¹H-NMR and ¹³C-NMR) methods. Further, the catalytic efficiency of all the complexes have been investigated for Suzuki and Sonogashira coupling reaction of various aryl halides.     

Pd(II) complexes of N,S-heterocyclic carbenes with pendant and coordinated allyl function and their Suzuki coupling activities

3-(2-Propenyl)benzothiazolium bromide () provides a direct and simple entry to Pd(ii) complexes with N,S-heterocyclic carbene (NSHC) ligands functionalized with an allyl pendant with hemilabile potential. Addition of salt to Pd(OAc)(2) eliminates HOAc and affords the bis(carbene) complexes cis-[PdBr(2)(NHSC)(2)] (cis-, NSHC = 3-(2-propenyl)benzothiazolin-2-ylidene) and trans-[PdBr(2)(NHSC)(2)] (trans-) along with the monocarbene complexes [PdBr(2)(NSHC)] () and trans-[PdBr(2)(benzothiazole-kappaN)(NSHC)] () as minor side products. Salt-metathesis of cis- with AgO(2)CCF(3) yields the mixed dicarboxylato-bis(carbene) complex cis-[Pd(O(2)CCF(3))(2)(NSHC)(2)] (). Complexes cis-, trans- and were characterized by multinuclear NMR spectroscopies, ESI mass spectrometry and elemental analysis. The molecular structures of complexes cis-, and have been determined by X-ray single crystal diffraction. Complexes cis- and as well as an in situ mixture of Pd(OAc)(2) and salt are active toward Suzuki-Miyaura coupling of aryl bromides and activated aryl chlorides giving good conversions.     

Seven-membered Pd(II) complexes containing symmetric phosphorus ylides: Synthesis,characterization and high catalytic activity toward Suzuki cross-coupling reactions

The reaction of 1,2-bis(diphenylphosphino)ethane (dppe) with various ketones in acetone produces the new phosphonium salts [RC(O)CH₂PPh₂(CH₂)₂PPh₂CH₂C(O)R]X₂ (R = 2-naphtyl, X = Br (1); R = 2,4-dichlorophenyl, X = Cl (2); R = 3-nitrophenyl, X = Br (3)). Further treatment with a base gives the symmetrical phosphorus ylides, RC(O)CHPPh₂(CH₂)₂PPh₂CHC(O)R (R = 2-naphtyl (4), 2,4-dichlorophenyl (5), 3-nitrophenyl (6)). These ligands react with Pd(II) chloride to form C,C-chelated complexes with the composition [RC(O)CHPPh₂(CH₂)₂PPh₂CHC(O)R]PdCl₂, where R = 2-naphtyl (7), 2,4-dichlorophenyl (8), 3-nitrophenyl (9). These compounds have been characterized by elemental analysis and spectroscopic methods and consist of seven-membered rings formed by the coordination of the ligands through the two ylidic carbon atoms to the metal center. The structure of compound 5 has been characterized crystallographically. The palladium complex 9 is employed in the Suzuki cross-coupling reaction between phenylboronic acid and several aryl halides. It was found to be a competent catalyst for a variety of substrates to afford the coupled products in high yields using DMF as a solvent. The biaryl products were obtained under aerobic conditions in short reaction times with a lower loading of the catalyst (0.001 mol%).     

Synthesis,characterization and catalytic activity of new aminomethyldiphosphine–Pd(II) complexes for Suzuki cross‐coupling reaction

A new range of CF₃‐substituted aminomethyldiphosphine (P―C―N) ligands ((C₆H₅)₂PCH₂)₂NR (R = ―C₆H₄(2‐CF₃) ( 1 ), ―C₆H₄(3‐CF₃) ( 1b ) has been synthesized from 2‐(trifluoromethyl)aniline and 3‐(trifluoromethyl)aniline with diphenylphosphine. The aminomethyldiphosphine ligands were reacted with Pd(cod)Cl₂ to give corresponding metal complexes, PdLCl₂ ( 2a , 2b ). The aminomethyldiphosphine–palladium compounds were characterized by utilizing several methods including NMR (¹H, ¹³C, ³¹P) and elemental analysis. These compounds were used as catalysts in Suzuki cross‐coupling reaction of aryl chlorides and bromides. The effect of base was also investigated in this current project. CF₃‐substituted aminomethyldiphosphine–palladium complexes were found to be efficient catalysts in Suzuki cross‐coupling reaction of activated and deactivated aryl boronic acids. Copyright © 2013 John Wiley & Sons, Ltd.     

Pd(II) complexes with mixed benzothiazolin-2-ylidene and phosphine ligands and their catalytic activities toward C-C coupling reactions

Novel Pd(II) mixed N,S-heterocyclic carbene (NSHC)-phosphine complexes of the general formula [PdBr(2)(NSHC)(PR(3))] were obtained from bridge cleavage of dinuclear NSHC complexes of type [PdBr(2)(NSHC)](2) [NSHC = 3-benzylbenzothiazolin-2-ylidene and 3-propylbenzothiazolin-2-ylidene] with triphenylphosphine, tricyclohexylphosphine and 2-diphenylphosphanyl-pyridine. All complexes have been fully characterized by (1)H and (13)C NMR spectroscopy, ESI mass spectrometry and elemental analysis. The X-ray crystal structures of complexes 3-8 are reported. The complexes exhibit moderate to good catalytic activity in the Suzuki-Miyaura coupling reaction of aryl bromides and chlorides.     

Synthesis and characterization of multimeric salicylaldimine thiosemicarbazones and their Pd(II) and Pt(II) complexes

A series of di- and trithiosemicarbazone ligands as well as their Pd(II) and Pt(II) 1,3,5-triaza-7-phosphaadamantane (PTA) complexes have been synthesised using templated reactions between various substituted salicylaldimine thiosemicarbazone ligands and metal precursors of the general formula cis-[M(PTA)₂Cl₂], where M = Pd or Pt. Characterization of these complexes was achieved using various analytical and spectroscopic techniques: elemental analysis, ESI-MS, FT-IR, and NMR (¹H, ¹³C{¹H} and ³¹P{¹H}) spectroscopy. The data revealed tridentate (O-N-S) coordination of the thiosemicarbazone moieties via the imine nitrogen, thiolato sulfur and phenolic oxygen to each metal center. In vitro biological evaluation of selected compounds was conducted against WHCO1 oesophageal cancer cells. Some of the multimeric compounds display some promising biological activity.     

Synthesis of neutral (Pd(II), Pt(II)), cationic (Pd(II)), and water-induced anionic (Pd(II)) complexes containing new mesocyclic thioether-aminophosphonite ligands and their application in the Suzuki cross-coupling reaction

Mesocyclic thioether-aminophosphonite ligands, {-OC10H6(mu-S)C10H6O-}PNC4H8O (2a, 4-(dinaphtho[2,1-d:1',2'-g][1,3,6,2]dioxathiaphosphocin-4-yl)morpholine) and {-OC10H6(mu-S)C10H6O-}PNC4H8NCH3 (2b, 1-(dinaphtho[2,1-d:1',2'-g][1,3,6,2]dioxathiaphosphocin-4-yl)-4-methylpiperazine) are obtained by reacting {-OC10H6(mu-S)C10H6O-}PCl (1) with corresponding nucleophiles. The ligands 2a and 2b react with (PhCN)2PdCl2 or M(COD)Cl2 (M = Pd(II) or Pt(II)) to afford P-coordinated cis-complexes, [{(-OC10H6(mu-S)C10H6O-)PNC4H8X-kappaP}2MCl2] (3a, M = Pd(II), X = O; 3b, M = Pd(II), X = NMe; 4a, M = Pt(II), X = O; 4b, M = Pt(II), X = NMe). Compounds 2a and 2b, upon treatment with [Pd(eta3-C3H5)Cl]2 in the presence of AgOTf, produce the P,S-chelated cationic complexes, [{(-OC10H6(mu-S)C10H6O-)PNC4H8X-kappaP,kappaS}Pd(eta3-C3H5)](CF3SO3) (5a, X = O and 5b, X = NMe). Treatment of 2a and 2b with (PhCN)2PdCl2 in the presence of trace amount of H2O affords P,S-chelated anionic complexes, [{(-OC10H6(mu-S)C10H6O-)P(O)-kappaP,kappaS}PdCl2](H2NC4H8X) (6a, X = O and 6b, X = NMe), via P-N bond cleavage. The crystal structures of compounds 1, 2a, 2b, 4a, and 6a are reported. Compound 6a is a rare example of crystallographically characterized anionic transition metal complex containing a thioether-phosphonate ligand. Most of these palladium complexes proved to be very active catalysts for the Suzuki-Miyaura reaction with excellent turnover number ((TON), up to 9.2 x 10(4) using complex 6a as a catalyst).     

Synthesis and characterisation of β-carboalkoxyruthenium(II) complexes

Methyl, ethyl, and butyl acrylates have been found to insert into the hydridoruthenium complex, HRuClCO(PPh₃)₃ under mild conditions to give RuC σ-bonded mononuclear complexes of the type RuClCO(PPh₃)₂CH₂CH₂COOR. The ruthenium atom is six coordinated in these complexes     

Synthesis and characterisation of new pyrazole-phosphinite ligands and their ruthenium(II) arene complexes

The new potentially bidentate pyrazole-phosphinite ligands [(3,5-dimethyl-1H-pyrazol-1-yl)methyl diphenylphosphinite] (L¹) and [2-(3,5-dimethyl-1H-pyrazol-1-yl)ethyl diphenylphosphinite] (L²) were synthesised and characterised. The reaction of L¹ and L² with the dimeric complexes [Ru(η⁶-arene)Cl₂]₂ (arene = p-cymene, benzene) led to the formation of neutral complexes [Ru(η⁶-arene)Cl₂(L)] (L = L¹, L²) where the pyrazole-phosphinite ligand is κ¹-P coordinated to the metal. The subsequent reaction of these complexes with NaBPh₄ or NaBF₄ produced the [Ru(η⁶-p-cymene)Cl(L²)][BPh₄] and [Ru(η⁶-benzene)Cl(L²)][BF₄] compounds which contain the pyrazole-phosphinite ligand κ²-P,N bonded to ruthenium. All the complexes were fully characterised by analytical and spectroscopic methods. The structure of the complex [Ru(η⁶-p-cymene)Cl(L²)][BPh₄] was also determined by a X-ray single crystal diffraction study.     

Aqueous Suzuki coupling reaction catalyzed by water-soluble diimine/Pd(II) systems

A series of water-soluble diimine ligands were applied for the Suzuki reaction of arylbromide in different media. Low loading of catalyst (0.01 mol%) were necessary for the coupling reaction to proceed in water or water/ethanol. The catalytic system was found to tolerate a broad range of functional groups.     

Schiff bases of 1′-hydroxy-2′-acetonaphthone containing chalcogen functionalities and their complexes with and (p-cymene)Ru(II), Pd(II), Pt(II) and Hg(II): Synthesis, structures and applications in C-C coupling reactions

Schiff bases of 1′-hydroxy-2′-acetonaphthone (HAN) containing chalcogen functionalities, 1-HO-C₁₀H₆-2-CH₃)CN-(CH₂)_nEC₆H₄-4-R (R = H or OMe; n = 2 or 3; E = S (L¹-L²), Se (L³-L⁴) or Te (L⁵-L⁶)) have been synthesized in yield 90-95%. They show characteristic ¹H, ¹³C{¹H} ⁷⁷Se{¹H} and ¹²⁵Te{¹H} (in case of selenated and tellurated species, respectively) NMR spectra. Their complexation with Pd(II), Pt(II), Hg(II) and (p-cymene)Ru(II) has been explored. The single-crystal structures of ligands L¹, L³ and L⁶ and complexes of Pd(II) with L¹, L², L³ and L⁵ have been determined. The geometry of Pd is close to square planar in all the complexes and the ligands coordinate in a uni-negative tridentate mode. The Pd-N bond lengths are in the range 1.996(7)-2.019(5) ?. The Pd-Se bond distance is 2.3600(5) ? whereas Pd-Te is 2.5025(7) ?. The Pd(II) complexes of L¹-L⁵ have been found promising as homogeneous catalyst for Heck and Suzuki reactions. The yields obtained were up to 85%.     

Catalytic activity of Fe(II) and Cu(II) PNP pincer complexes for Suzuki coupling reaction

Iron and copper PNP pincer complexes of the type [Fe(L)SO₄] and [Cu(L)OCOCH₃] are reported and represented as C‐1 and C‐2 catalyst. Both the complexes were synthesized using bis(diphenylphosphino)pyridine‐2,6‐diamine [L], and salts of ‘Fe’ and ‘Cu’ by direct coordination method. The as synthesized complexes were characterized using FTIR, UV–Vis, mass analysis and TGA. The effect of reaction time, catalyst load, solvent and base on the reaction between phenylboronic acid and para substituted bromobenzenes in the presence of the catalysts were investigated for evaluating the catalytic efficiency of the complexes. The results obtained highlight the enhanced C‐C coupling reactions with the use of 0.4 mol% of the catalyst C‐1 in 14 h and 0.6 mol% of C‐2 in 16 h respectively with Cs₂CO₃ base and ACN as solvent media. Of the two complexes reported, C‐1 with iron as catalytically active metal is more stable and active towards coupling which is reflected in its better coupling yields in lesser reaction time compared to copper bearing C‐2 complex.     

Synthesis,characterisation and reactions of pentacoordinated iridium(I) complexes

Stable, pentacoordinated iridium(I) complexes have been synthesised by the replacement of the chlorine in IrCO(PPh₃)₂Cl by bidentate chelating ligands such as β-diketones, N-benzoyl-N-phenyl hydroxylamine, salicylaldehyde, 8-hydroxyquinoline, 2-hydroxybenzophenone and 2-hydroxy 4-methoxybenzophenone. Most of them gave stable oxygen adducts IrCO(PPh₃)₂(L)O₂ and all of them underwent oxidative addition with bromine in methylene chloride giving IrCO(PPh₃)₂(L)Br₂. These chelated iridium(I) compounds reacted with liquid sulphur dioxide to produce two types of SO₂ insertion products.