New axially dissymmetric ligand recoverable with fluorous solvent

Axially dissymmetric ligands with perfluoroalkyl groups, (Ra)-2,2′-bis[(R)-1-hydroxy-1H-perfluorooctyl]biphenyl [(Ra)-(R)₂-1c] and its enantiomer, have been synthesized successfully by the coupling reaction of the corresponding aryl bromide using Ni(COD)₂. These ligands showed much higher asymmetric induction in the reaction of various aldehydes with diethylzinc than the trifluoromethyl (1a) or pentafluoroethyl (1b) analogues. Furthermore, 1c was recovered quantitatively by extraction with a fluorous solvent from the reaction mixture due to its high fluorine content. The recovered ligand 1c was pure enough to be reused without purification. The efficiency of 1c as the chiral ligand was not decreased at all even after seven times recycling.     

Arylation of β-methallyl alcohol catalyzed by Pd(OAc)2 in combination with P(t-Bu)3: application to fragrance synthesis

Pd(OAc)₂ in combination with P(t-Bu)₃ catalyzes the coupling of β-methallyl alcohol with 1-bromo-3,4-(methylenedioxy)benzene (1a), 1-bromo-4-methoxybenzene (1b), or 1-bromo-4-tert-butylbenzene (1c). The reaction affords the corresponding 2-methyl-3-aryl-propanals, which are valuable floral fragrances. With 1a or 1b high reaction rates are obtained at 130 °C using NMP/water mixtures and an inorganic base such as Na₂CO₃. The chemoselectivity of the reaction is almost complete, so that the process appears practically feasible. In contrast, the coupling of β-methallyl alcohol with 1c proceeds with low reaction rates.     

Convenient and efficient Suzuki-Miyaura cross-coupling reactions catalyzed by palladium complexes containing N,N,O-tridentate ligands

N,N,O-Tridentate ligands 1-9 were prepared from the condensation of amines with nine aromatic aldehydes or ketones. These ligands are thermally stable and neither air- nor moisture-sensitive. Combination of either 2-methoxy-6-[(pyridine-2-ylmethylimino)-methyl]-phenol, 1 or 2-(benzothiazol-2-yl-hydrazonomethyl)-4,6-di-tert-butyl-phenol, 6 with Pd(OAc)₂ furnished an excellent catalyst precursor for the Suzuki-Miyaura cross-coupling of various aryl bromides with arylboronic acids. The effects of varying solvents, bases, and ligand/palladium ratios on the performance of the coupling reaction were investigated. The molecular structures of both free ligand 1 and its palladium acetate complex 10 were determined by single-crystal X-ray diffraction methods. The DFT studies revealed that the catalytic performance of palladium complexes involving this type of a ligand may differ greatly upon a small variation in its structure.     

Silver N-heterocyclic carbene complexes as initiators for bulk ring-opening polymerization (ROP) of l-lactides

Synthetic, structural and catalysis studies of two silver complexes namely, {[1-(2,4,6-trimethylphenyl)-3-(N-phenylacetamido)imidazol-2-ylidene]₂Ag}⁺Cl⁻1b, supported over an amido-functionalized N-heterocyclic carbene ligand, and [1-(i-propyl)-3-(benzyl)imidazol-2-ylidene]AgCl 2b, supported over a non-functionalized N-heterocyclic carbene ligand, are reported. Specifically, 1b, a cationic complex bearing 2:1 NHC ligand to metal ratio, was obtained from the reaction of 1-(2,4,6-trimethylphenyl)-3-(N-phenylacetamido)imidazolium chloride 1a with Ag₂O in 52% yield. The corresponding 1a was synthesized by the alkylation reaction of 1-(2,4,6-trimethylphenylimidazole) with N-phenyl chloroacetamide in 73% yield. The other silver complex 2b, a neutral complex bearing 1:1 NHC ligand to metal ratio, was obtained from the reaction of 1-(i-propyl)-3-(benzyl)imidazolium chloride 2a with Ag₂O in 42% yield. The 2a was synthesized by the alkylation reaction of 1-(i-propylimidazole) with benzyl chloride in 45% yield. The molecular structures of the imidazolium chloride, 1a, and the silver complexes, 1b and 2b, have been determined by X-ray diffraction studies. The silver complexes, 1b and 2b, successfully catalyze bulk ring-opening polymerization (ROP) of l-lactides at elevated temperatures under solvent-free melt conditions producing moderate to low molecular weight polylactide polymers having narrow molecular weight distributions.     

Selenoether ligand assisted Heck catalysis

Selenoether ligands, 2,2′-methylenebis(selanediyl)bis(2,1-phenylene)dimethanol (5), (2,2′-(ethane-1,2-diylbis(selanediyl))bis(2,1-phenylene))dimethanol (6) and (2-(benzylselanyl)phenyl)methanol (7) have been synthesized by reducing di-o-formylphenyl diselenide and reacting the in situ generated selenolate with dibromomethane, 1,2-dibromoethane and benzyl chloride, respectively. The ligands, bis(2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)phenylselanyl)methane (8) and 1,2-bis(2-(4,4-dimethyl-4,5-dihydrooxazol-2-yl)phenylselanyl)ethane (9) have been synthesized similarly from bis[2-(4,4-dimethyl-2-oxazolinyl)phenyl] diselenide using electrophiles dibromomethane and 1,2-dibromoethane, respectively. Activity of ligands 5-9 along with 2-(2-(benzylselanyl)phenyl)-4,4-dimethyl-4,5-dihydrooxazole (10) and 1-(2-(benzylselanyl)phenyl)-N,N-dimethylmethanamine (11) were examined for the Heck reaction of aryl halides with olefins. Bidentate Se,N ligand 11 was found to be the best one in the series and constitutes an efficient phosphine-free catalytic system with PdCl₂. The catalytic system showed moderate activity for the coupling of activated aryl chlorides in the presence of tetra-n-butyl ammonium bromide (TBAB). Complexes [10-PdCl₂] (12) and [11-PdCl₂] (13) have shown marginally better activity in comparison to the in situ generated catalysts from PdCl₂ and 10 and 11, respectively in the coupling of 4-bromoacetophenone with n-butylacrylate. Ligand 9 and complex 13 have been characterized by single crystal X-ray diffraction analysis.     

Syntheses and characterizations of methylpalladium complexes bearing a biphenyl-based bulky phosphine ligand: Weak interactions suggested by NBO and QTAIM analyses

A methylpalladium chloride complex bearing a biphenyl-based bulky phosphine ligand, ^tBu₂P(biphenyl-2-yl) (1), namely [Pd(1)(Me)Cl]₂ (=8), was synthesized by the reaction of (cod)Pd(Me)Cl with 1. A following reaction of 8 with AgOTf gave the corresponding triflate complex, Pd(1)(Me)OTf (=9). These complexes were fully characterized by NMR spectroscopy and structurally characterized by X-ray crystallographic study. In the solid state of 8, biphenyl-based phosphine ligand 1 played a role of monodentate phosphine ligand with a possible weak η¹-coordination from the phenyl ring at 2′-position of 1. On the other hand, phosphine ligand 1 in 9 showed a bidentate coordination mode consist of σ-donation of the phosphine and η²-coordination of the phenyl ring at 1′- and 2′-positions. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) calculations also supported the existence of these weak interactions.     

Synthesis and characterization of titanium and zirconium complexes with silicone-bridged phenoxycyclopentadienyl ligands

Dimethylsilyl(2,3,4,5-tetramethylcyclopentadienyl)(3-tert-butyl-5-methyl-2-phenoxy)titanium dichloride (1a), a useful catalyst precursor for olefin copolymerization, was synthesized at high yield starting from allyl-protected phenolic ligand 3a,which was first treated with 2 equiv. of n-BuLi to selectively give the dilithium salt of 3a along with 1-heptene, a coupling product of a protected allyl ether moiety and butyl anion. Addition of TiCl₄ to the resulting dilithium salt of 3a in toluene afforded 1a in 50% isolated yield. This methodology could be applied to the preparation of related titanium and zirconoium complexes 1b-1d, 8 with silicone-bridged Cp-phenoxy ligands, whereas the reaction starting from methyl-protected precursor 2a did not produce the zirconium complex 8. Copolymerization of ethylene and 1-hexene with the newly prepared complexes was also investigated.     

Enantioselective synthesis of axially chiral 1-(1-naphthyl)isoquinolines and 2-(1-naphthyl)pyridines through sulfoxide ligand coupling reactions

Racemic 1-(1′-isoquinolinyl)-2-naphthalenemethanol rac-12 was prepared through a ligand coupling reaction of racemic 1-(tert-butylsulfinyl)isoquinoline rac-7 with the 1-naphthyl Grignard reagent 10. Resolution of rac-12 was achieved through chromatographic separation of the Noe-lactol derivatives 14 and 15, providing (R)-(−)-12 of >99% ee and (S)-(+)-12 of 90% ee. The ligand coupling reaction of optically enriched sulfoxide (S)-(−)-7 (62% ee) with Grignard reagent 10 furnished rac-12, with the absence of stereoinduction resulting from competing rapid racemisation of the sulfoxide 7. Reaction of optically enriched (S)-(−)-7 with 2-methoxy-1-naphthylmagnesium bromide was also accompanied by racemisation of the sulfoxide 7, and furnished optically active (+)-1-(2′-methoxy-1′-naphthyl)isoquinoline (+)-3b in low enantiomeric purity (14% ee). The absolute configuration of (+)-3b was assigned as R using circular dichroism spectroscopy, correcting an earlier assignment based on the Bijvoet method, but in the absence of heavy atoms. Optically active 2-pyridyl sulfoxides were found not to undergo racemisation analogous to the 1-isoquinolinyl sulfoxide 7, with the ligand coupling reactions of (R)-(+)- and (S)-(−)-2-[(4′-methylphenyl)sulfinyl]-3-methylpyridines, (R)-(+)-17 and (S)-(−)-17, with 2-methoxy-1-naphthylmagnesium bromide providing (−)- and (+)-2-(2′-methoxy-1′-naphthyl)-3-methylpyridines, (−)-18 and (+)-18, in 53 and 60% ee, respectively. The free energy barriers to internal rotation in 3b and 18 have been determined, and the isoquinoline (R)-(−)-12 examined as a ligand in the enantioselectively catalysed addition of diethylzinc to benzaldehyde; (R)-(−)-12 was also converted to (R)-(−)-N,N-dimethyl-1-(1′-isoquinolinyl)-2-naphthalenemethanamine (R)-(−)-19, and this examined as a ligand in the enantioselective Pd-catalysed allylic substitution of 1,3-diphenylprop-2-enyl acetate with dimethyl malonate.     

Synthesis and structures of dinuclear iron, molybdenum and tungsten complexes derived from (PhCHCHPh)-coupled bis(cyclopentadiene)

Reductive coupling of phenylfulvene with amalgamated calcium metal followed by hydrolysis yields CpPhCHCHPhCp (1) in high yield. Refluxing ligand 1 and Fe(CO)₅ in xylene produces (PhCHCHPh)-coupled bis(cyclopentadienyl) tetracarbonyl diiron (PhCHCHPh)[(η⁵-C₅H₄)Fe(CO)₂]₂ (2) as a mixture of meso (2-meso) and racemic isomers (2-rac). The pure racemic isomers of the Mo and W analogues (3-rac and 4-rac) have been synthesized by lithiation of ligand 1 and addition of (MeCN)₃M(CO)₃ (M = Mo, W) followed by oxidation with 2 equiv. of ferrocenium tetrafluoroborate. All the new complexes have been fully characterized. The molecular structures of 1-meso, 2-meso, 2-rac, 3-rac, and 4-rac have been determined by X-ray diffraction analysis.     

The synthesis of oligoether-substituted benzimidazolium bromides and their use as ligand precursors for the Pd-catalyzed Heck coupling in water

The oligoether-substituted (CH₃(OCH₂CH₂)_n-; n = 1, 2 or 3) benzimidazolium bromides (3-7) and oligoether-linked (-CH₂(CH₂OCH₂)_nCH₂-, n = 1, 2 or 3) bisbenzimidazolium dibromides (8-13) were prepared by quarternization of N-substituted benzimidazoles (1 and 2) with the bulky benzyl bromides (ArCH₂Br: Ar = C₆H₂(CH₃)₃-2,4,6 and C₆(CH₃)₅). trans-Bis(carbene) palladium(II) complexes 14 and 15 derived from 4 and 6 were synthesized by using Ag complexes as carbene-transfer agents in dichloromethane at ambient temperature. In addition, the reactions of 4 and 6 with Pd(OAc)₂ and NaBr gave the Pd(II) dimers 16 and 17 which can readily be cleaved by triphenylphosphine to afford the benzannulated monocarbene (NHC) monophosphine Pd(II) complexes [PdBr₂(NHC)(PPh₃)] (18 and 19). All compounds have been fully characterized by using elemental analysis, ¹H, ¹³C and ³¹P NMR spectroscopies. X-ray diffraction studies on single crystals of 19a and 19b confirm the cis square planar geometry. In situ formed complexes from Pd(OAc)₂ and benzimidazolium salts (3-13) and preformed Pd(II) complexes 14, 15, 18 and 19 were tested as catalyst for the Heck coupling reaction in water. The influence of the oligoether and benzyl substituents on N atoms and CH₃-substituents on the 5,6-positions of benzimidazole frame were investigated under the same conditions in the Heck coupling reaction. In situ formed catalysts showed better conversions than the isolated Pd(II) complexes. The length of the oligoether spacer significantly increases the activity. The salts with two benzimidazole moieties connected by an oligoether as the spacer 8-13 showed similar catalytic activities in the Heck coupling reaction with the mono salts 3-7 bearing corresponding oligoethers on the N atom.     

Salen-ligands based on a planar-chiral hydroxyferrocene moiety: Synthesis, coordination chemistry and use in asymmetric silylcyanation

Condensation of the O-protected hydroxyferrocene carbaldehyde (S_p)-1 with suitable diamines, followed by liberation of the hydroxyferrocene moiety leads to a new type of ferrocene-based salen ligands (3). While the use of ethylenediamine in the condensation reaction yields the planar-chiral ethylene-bridged ligand [(S_p,S_p)-3a], reaction with the enantiomers of trans-1,2-cyclohexylendiamine gives rise to the corresponding diastereomeric cyclohexylene-bridged systems [(S,S,S_p,S_p)-3b and (R,R,S_p,S_p)-3c], which feature a combination of a planar-chiral ferrocene unit with a centrochiral diamine backbone. Starting with the ferrocene-aldehyde derivative (R_p)-1, the enantiomeric ligand series (3d/e/f) is accessible via the same synthetic route.The (S_p)-series of these newly developed N₂O₂-type ligands was used for the construction of the corresponding mononuclear bis(isopropoxy)titanium (4a/b/c), methylaluminum (5a/b/c) and chloroaluminum-complexes (6a/b/c), which were isolated in good yields and identified by X-ray diffraction in several cases. The aluminum complexes (5/6) were successfully used in the Lewis-acid catalyzed addition of trimethylsilylcyanide to benzaldehyde, yielding the corresponding cyanohydrins in 45-62% enantiomeric excess.     

Dendritic polyallyl and polyferrocenyl bipyridine ligands: Synthesis, MALDI-TOF characterization and ruthenium(II) complexation studies

A series of 6- and 18-armed dendritic polyallyl- and polyferrocenyl-containing bipyridine ligands were synthesized through the coupling reaction of 4,4′-bis(bromomethyl)-2,2′-bipyridine with AB₃ and AB₉ dendrons. All these bipyridine ligands were successfully characterized using standard physico-chemical techniques as well as MALDI-TOF mass spectrometric analysis. The complexation studies of these ligands toward RuCl₂(bpy)₂ indicated that, in contrast to the bulky 18-ferrocenyl bipyridine ligand 7, the 6-allyl 4 and the 18-allyl 5 bipyridine ligands react with Ru(bpy)₂Cl₂ to give the corresponding ruthenium(II) complexes 9 and 10. In the case of ligand 7, the steric bulk of the two nonaferrocenyl wedges at the 4,4′-position of the bipyridine moiety prevents the conversion of the transoid structure of the ligand to the cisiod structure needed for chelation to the metal. Thus, the 18-ferrocenyl ruthenium(II) dendrimer was not obtained. Metallodendrimers 9 and 10 have been characterized by a combination of analytical methods, especially MALDI-TOF mass spectrometric techniques. The hydrogenation of the 6-allyl ruthenium(II) dendrimer 9 in the presence of Pd/C catalyst gave the expected n-propyl complex 11. This reaction constitutes a new way for the direct synthesis of alkyl bipyridine metallodendrimers. The coordination of the alkene dendritic bipyridine ligand to the metal before the catalytic hydrogenation is absolutely necessary, because of their poisoning effect for the catalyst.     

Di-t-butyl(ferrocenylmethyl)phosphine: air-stability, structural characterization, coordination chemistry, and application to palladium-catalyzed cross-coupling reactions

Di-t-butyl(ferrocenylmethyl)phosphine (1) has been isolated and structurally characterized. This ligand was found to be reasonably air stable as a solid and it has been shown to possess electron donating ability similar to that of tri-i-propylphosphine. A palladium catalyst bearing this ligand performed room temperature Suzuki-Miyaura coupling reactions with aryl bromides. Modest Heck coupling reactivity with aryl bromides was also observed at 100 °C. Complexation of 1 with Pd₂(dba)₃ led to formation of (1)₂Pd⁰. Addition of 4-bromoanisole to solutions containing both 1 and Pd₂(dba)₃ led to formation of an oxidative addition product when 1:Pd ratios were ?1. With a 2:1 ratio of 1:Pd, monophosphine complex formation and oxidative addition were significantly inhibited.     

trans-Spanning ferrocene amidodiphosphine ligand: Synthesis, palladium complexes and catalytic use in Suzuki-Miyaura cross-coupling

Amide coupling between [2-(diphenylphosphino)phenyl]methylamine and 1′-(diphenylphosphino)ferrocene-1-carboxylic acid (Hdpf) afforded a novel diphosphine-amide, 1-{N-[(2-(diphenylphosphino)phenyl)methyl]carbamoyl}-1′-(diphenylphosphino)ferrocene (1), which was subsequently studied as a ligand for palladium(II) complexes. Depending on the metal precursor, the following complexes were isolated: [PdCl₂(1-κ²P,P′)] (2), [PdCl(Me)(1-κ²P,P′)] (3), [(μ-1){PdCl₂(PBu₃)}₂] (4) and [(μ-1){PdCl(L^NC)}₂] (L^NC = 2-[(dimethylamino-κN)methyl]phenyl-κC¹), featuring this ligand either as a trans-chelating or as a P,P′-bridging donor. The crystal structure of 2·1.25CH₂Cl₂ was established by X-ray crystallography, corroborating that 1 coordinates as a trans-spanning diphosphine without any significant distortion to the coordination sphere. Complex 2 together with a catalyst prepared in situ from 1 and palladium(II) acetate were tested in Suzuki-Miyaura reaction of aryl bromides with phenylboronic acid in dioxane.     

Synthesis and characterizations of N,N,N′,N′-tetrakis (diphenylphosphino)ethylendiamine derivatives: Use of palladium(II) complex as pre-catalyst in Suzuki coupling and Heck reactions

Oxidation of N,N,N′,N′-tetrakis(diphenylphosphino)ethylendiamine (1) with elemental sulfur and selenium gives the corresponding sulfide and selenide, respectively, [(Ph₂P(E))₂NCH₂CH₂N(P(E)Ph₂)₂] (E: S 1a, Se 1b). Complexes of 1 [(M₂Cl₄){(Ph₂P)₂NCH₂CH₂N(PPh₂)₂}] (M: Ni(II) 1c, Pd(II) 1d, Pt(II) 1e) were prepared by the reaction of 1 with NiCl₂ or [MCl₂(COD)] (M = Pd, Pt). The new compounds were characterized by NMR, IR spectroscopy and elemental analysis. The catalytic activity of Pd(II) complex 1d was tested in the Suzuki coupling reaction and Heck reaction. The palladium complex 1d catalyses the Heck reaction between styrene and aryl bromides as well as Suzuki coupling reaction between phenylboronic acid and arylbromides affording stilbenes and biphenyls in high yield, respectively.     

Syntheses, crystal structures and properties of Co(II) complexes with N,N′-bis(3-pyridylmethyl)-1,4-benzenedimethyleneimine (bpb), and Cd(II), Hg(II) complexes with reduced bpb

Five novel coordination polymers, [Co(bpb)₂Cl₂] (1), [Co(bpb)₂(SCN)₂] (2), [Cd(H₄bpb)_0.5(dmf)(NO₃)₂] (3), [Cd₂(H₄bpb)Br₄] (4), and [Hg₂(H₄bpb)I₄] (5) [bpb=N,N′-bis(3-pyridylmethyl)-1,4-benzenedimethyleneimine, H₄bpb=N,N′-bis(3-pyridylmethyl)-1,4-benzenedimethylamine], were synthesized and their structures were determined by X-ray crystallography. In the solid state, complex 1 is a 1D hinged chain, while 2 has 2D network structure with the ligand bpb serving as a bridging ligand using its two pyridyl N atoms. The imine N atoms keep free of coordination and bpb acts as a bidentate ligand in both 1 and 2. Complexes 3, 4, and 5 with reduced bpb ligand, i.e. H₄bpb, show similar 2D network structure, in which ligand H₄bpb serves as a tetradentate ligand. Thermogravimetric analyses for complexes 1-5 were carried out and found that they have high thermal stability. The magnetic susceptibilities of compounds 1, 2 were measured over a temperature range of 75-300 K.     

Endo and exo cyclometallated iron carbonyl complexes derived from N-(N′-methyl-2-pyrrolylmethylidene)-2-thienylmethylamine

The reaction of N-(N′-methyl-2-pyrrolylmethylidene)-2-thienylmethylamine (1) with Fe₂(CO)₉ in refluxing toluene gives endo cyclometallated iron carbonyl complexes 2 and 5, exo cyclometallated iron carbonyl complex 3, and unexpected iron carbonyl complex 4. Complexes 2, 3, and 5 are geometric isomers. Complex 5 differs from complex 2 in the switch of the original substituent from α to β position of the pyrrolyl ring, and the pyrrolyl ring bridges to the diiron centers in μ-(3,2-η¹:η²) coordination mode in stead of μ-(2,3-η¹:η²). In complex 4, the pyrrolyl moiety of the original ligand 1 has been displaced by a thienyl group, which comes from the same ligand. Single crystals of 2, 3, and 5 were subjected to the X-ray diffraction analysis. The major product 2 undergoes: (i) thermolysis to recover the original ligand 1; (ii) reduction to form a hydrogenation product, 6, of the original ligand; (iii) substitution to form a monophosphine-substituted complex 7; (iv) chemical as well as electrochemical oxidation to produce a carbonylation product, γ-butyrolactam 8.     

Stilbene like carbazole dimer-based electroluminescent materials

Two carbazole dimers (1 and 10) were synthesized from 9-ethyl-9H-carbazole-3-carbaldehyde and 6-bromo-9-ethyl-9H-carbazole-3-carbaldehyde by McMurry C-C coupling reaction. Palladium(0)-catalyzed C-N coupling reactions of 10 and various diarylamines result in the formation of stable carbazole derivatives in good yields. These compounds are fluorescent in blue to yellow region with moderate to good quantum yields. Also, they are thermally stable and capable of hole-transporting due to the presence of the carbazole moieties. The electroluminescent devices fabricated using 1, 2, and 3 as hole-transporters/emitters with a bilayer structure ITO/Cpd/TPBI or Alq₃/LiF/Al (Cpd=1, 2, and 3) exhibit good performance (e.g., η_ext=1.0-2.1%; η_p=0.9-1.9 lm/W; η_c=2.4-4.8 cd/A at a current density of 100 mA/cm²).     

Pyrazole-tethered phosphine ligands for Pd(0): useful catalysts for Stille, Kumada and Hiyama cross-coupling reactions

Combination of 3,5-dimethyl-1-(2-(diphenylphosphino)phenyl)-1H-pyrazole, A, and 3-tert-butyl-5-methyl-1-(2-(diphenylphosphino)phenyl)-1H-pyrazole, B, with Pd₂(dba)₃ furnished excellent catalysts for Stille, Kumada and Hiyama cross-coupling reactions. Effects of solvents, bases and ligand/palladium ratio on efficiency of coupling reactions were studied. Molecular structures of palladium(II) complexes of A and B determined by single-crystal X-ray diffraction method revealed a close similarity of ligand arrangement around the metal centre.     

Catalytic applications of Cu-containing MOFs based on N-heterocyclic ligand in the oxidative coupling of 2,6-dimethylphenol

Two Cu^II complexes bearing a N-heterocyclic ligand, namely [Cu(SO₄)(pbbm)]_n (1) and {[Cu(Ac)₂(pbbm)] · CH₃OH}_n (2) (pbbm = 1,1′-(1,5-pentanediyl)bis-1H-benzimidazole) have been synthesized with the aim of exploiting new and potent catalysts. Single crystal X-ray diffraction shows that new polymeric complex 1 features 1-D double-chain framework. The catalytic studies on 1 and 2 indicate that they are efficient homogeneous catalysts for the oxidative coupling of 2,6-dimethylphenol (DMP) to poly(1,4-phenylene ether) (PPE) and diphenoquinone (DPQ) with H₂O₂ as oxidant and NaOMe as co-catalyst at room temperature. Optimal reaction conditions are obtained by examining the effects of solvent, the reaction time, temperature as well as the amounts of co-catalyst, catalyst and oxidant. Under the optimal conditions, the selectivity to PPE is almost up to 90% for both complexes, and the conversion of DMP is 85% for 1 and 90% for 2, comparable to those observed for highly active catalyst systems in the literature. Further comparison of their catalytic performances with those of the corresponding copper salt together with organic ligand, copper salt alone and free ligand reveals that the coordination of ligand to Cu^II ion plays a key role in generating the superior reactivities of complexes.