Oxidation of styrene and cyclohexene with TBHP catalyzed by copper(II) complex encapsulated in zeolite-Y

Reaction of monobasic tridentate Hacpy-oap (Hacpy-oap?=?Schiff base derived from 2-acetylpyridine and o-aminophenol) with Cu^IICl₂ in refluxing methanol results in formation of [Cu^II(acpy-oap)Cl]. DFT calculations have been used to optimize structure of the complex. [Cu^II(acpy-oap)Cl] has also been encapsulated in the nanocavity of zeolite-Y and its encapsulation ensured by various physico-chemical techniques. Neat as well as encapsulated complexes are active catalysts for oxidation of styrene and cyclohexene using tert-butylhydroperoxide. Reaction conditions for oxidation of these substrates have been optimized by concentration of oxidant, amount of catalyst, volume of solvent and temperature of the reaction mixture. [Cu^II(acpy-oap)Cl] does not leach metal ion during catalytic activity and is recyclable.     

Oxovanadium(IV) based coordination polymers and their catalytic potentials for the oxidation of styrene, cyclohexene and trans-stilbene

Reaction between 5,5′-methylenebis(salicylaldehyde) or 5,5′-dithiobis(salicylaldehyde) and 1,2-diaminocyclohexane in equimolar ratio leads to the formation of new polymeric chelating ligands [–CH₂(H₂sal-dach)–]_n (I) and [–S₂(H₂sal-dach)₂–]_n (II). These ligands react with [VO(acac)₂] in DMF to give coordination polymers [–CH₂{VO(sal-dach)·DMF}–]_n (1) and [–S₂{VO(sal-dach)·DMF}–]_n (2). Both complexes are insoluble in common solvents and exhibit a magnetic moment value of 1.74 and 1.78μ_B, respectively. IR spectral studies confirm the coordination of ligands through the azomethine nitrogen and the phenolic oxygen atoms to the vanadium. These complexes exhibit good catalytic activity towards the oxidation of styrene, cyclohexene and trans-stilbene using tert-butylhydroperoxide as an oxidant. Concentration of the oxidant and reaction temperature has been optimised for the maximum oxidation of these substrates. Under the optimised conditions, oxidation of styrene gave a maximum of 76% (with 1) or 85% (with 2) conversion having following products in order of selectivity: benzaldehyde > styreneoxide > 1-phenylethane-1,2-diol > benzoic acid. A maximum of 98% conversion of cyclohexene was obtained with both the catalysts where selectivity of cyclohexeneoxide varied in the order: 2 (62%) > 1 (45%). With the conversion of 33% (with 1) and 47% (with 2), oxidation of trans-stilbene gives benzaldehyde, benzil and trans-stilbeneoxide as major products.     

Copper(II) complex of monobasic tridentate ONN donor ligand: synthesis,encapsulation in zeolite-Y,characterization, and catalytic activity

Reaction between CuCl₂ and (Z)-2-(1-(2-(1H-benzo[d]imidazol-2-yl)ethylimino)ethyl)phenol (Hhap-aebmz) derived from o-hydroxyacetophenone (Hhap) and 2-aminoethylbenzimidazole (aebmz) gives [Cu^II(hap-aebmz)Cl]. Elemental analysis, magnetic susceptibility, spectral (IR and electronic) data, and single crystal X-ray studies confirm the distorted square planar structure of the complex. [Cu^II(hap-aebmz)Cl] has been encapsulated in the nano-cavity of zeolite-Y and its encapsulation is ensured by various physico-chemical techniques. The encapsulated complex has been used as a catalyst for oxidation of cyclohexene and phenol in the presence of H₂O₂. With nearly quantitative oxidation of cyclohexene, the selectivity of the oxidation products follows the order, 2-cyclohexene-1-ol (44%)?>?2-cyclohexene-1-one (40%)?>?cyclohexeneoxide (12%)?>?cyclohexane-1,2-diol (4%). Oxidation of phenol (65.7%) gives catechol (66.1%)?>?hydroquinone (32.9%).     

Oxovanadium(IV), copper(II) or cobalt(II) acetylacetone complexes immobilized on amino‐functionalized CMK‐3 for the aerobic epoxidation of styrene

Oxovanadium(IV), copper(II) and cobalt(II) acetylacetone complexes have been grafted onto amino‐modified CMK‐3‐O (VO‐NH₂‐CMK‐3, Cu‐NH₂‐CMK‐3 and Co‐NH₂‐CMK‐3,respectively) and the materials thus prepared were used as heterogeneous catalysts for the aerobic oxidation of styrene. X‐ray diffraction, nitrogen adsorption–desorption and transmission electron microscopy measurements confirmed the structural integrity of the mesoporous hosts, and spectroscopic characterization techniques (Fourier transform infrared, X‐ray photoelectron, Raman) and thermogravimetry confirmed the ligands and the successful anchoring of the acetylacetone complexes to the modified mesoporous support. VO‐NH₂‐CMK‐3 displayed a relatively good catalytic performance with 94.6% of styrene conversion using air as oxidant, while Cu‐NH₂‐CMK‐3 gave 99.6% of styrene conversion using tert‐butyl hydroperoxide as oxidant. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis, characterization and catalytic oxidation of cyclohexene with molecular oxygen with host (nanopores of zeolite-Y)/guest (Ni(II) complexes of 14- and 16-membered tetraaza dioxo diphenyl macrocyclic ligands) nanocomposite materials

Ni(II) complexes of [14]aneN₄: 1,5,8,12-tetraaza-2,9-dioxo-4,11-diphenylcyclotetradecane; [16]aneN₄: 1,5,9,13-tetraaza-2,10-dioxo-4,12-diphenylcyclohexadecane; Bzo₂[14]aneN₄: dibenzo-1,5,8,12-tetraaza-2,9-dioxo-4,11-diphenylcyclotetradecane and Bzo₂[16]aneN₄: dibenzo-1,5,9,13-tetraaza-2,10-dioxo-4,12-diphenylcyclohexadecane have been encapsulated in the nanopores of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of [bis(diamine)nickel(II)] (diamine = 1,2-diaminoethane, 1,3-diaminopropane, 1,2-diaminobenzene, 1,3-diaminobenzene); [Ni(N–N)₂]²⁺–NaY; in the nanopores of the zeolite-Y, and (ii) in situ condensation of the nickel(II) precursor complex with ethylcinnamate. The new host–guest nanocomposite materials (HGNM) were characterized by several techniques: chemical analysis and spectroscopic methods (FT-IR, UV/Vis, XRD and DRS) and the BET technique. These complexes were used for oxidation of cyclohexene with molecular oxygen.     

Iron(III), cobalt(II) and copper(II) complexes bearing 8‐quinolinol encapsulated in zeolite?Y for the aerobic oxidation of styrene

A series of Fe(III), Co(II) and Cu(II) complexes of 8‐quinolinol were encapsulated into the supercages of zeolite? Y and characterized by X‐ray diffraction, SEM, N₂ adsorption/desorption, FT‐IR, UV–vis spectroscopy, elemental analysis, ICP‐AES and TG/DSC measurements. The encapsulation was achieved by a flexible ligand method in which the transition metal cations were first ion‐exchanged into zeolite Y and then complexed with 8‐quinolinol ligand. The metal‐exchanged zeolites, metal complexes encapsulated in zeolite–Y plus non‐encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes always showed better activity than their respective non‐encapsulated counterparts. Moreover, the encapsulated iron complex showed good recoverability without significant loss of activity and selectivity within successive runs. Heterogeneity test for this catalyst confirmed its high stability against leaching of active complex species into solution. Copyright © 2011 John Wiley & Sons, Ltd.     

Synthesis,characterization, and catalytic oxidation of ethylbenzene over host (zeolite-Y)/guest (copper(II) complexes of tetraaza macrocyclic ligands) nanocomposite materials

Cu(II) complexes of 14- and 16-membered tetraaza macrocyclic ligands have been encapsulated in nanopores of zeolite-Y by a two-step process in the liquid phase: (1) adsorption of [bis(diamine)copper(II)] (diamine = 1,2-diaminoethane, 1,3-diaminopropane, 1,2-diaminobenzene, and 1,3-diaminobenzene); [Cu(N–N)₂]²⁺–NaY; in the nanopores of the zeolite-Y and (2) in situ condensation of the copper(II) precursor complex with ethylcinnamate. The new host–guest nanocomposite materials were characterized by chemical analysis and spectroscopic methods. The “neat” and encapsulated complexes exhibit good catalytic activity in the oxidation of ethylbenzene at 333 K, using tert-butyl hydroperoxide as the oxidant. Acetophenone was the major product though small amounts of o- and p-hydroxyacetophenones were also formed revealing that C–H bond activation takes place both at benzylic and aromatic ring carbon atoms.     

Synthesis, characterisation and catalytic activities of manganese(III) complexes of pyridoxal-based ONNO donor tetradenatate ligands

Reaction of Mn^II(CH₃COO)₂ with dibasic tetradentate ligands, N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-en, I), N,N′-propylenebis(pyridoxylideneiminato) (H₂pydx-1,3-pn, II) and 1-methyl-N,N′-ethylenebis(pyridoxylideneiminato) (H₂pydx-1,2-pn, III) followed by aerial oxidation in the presence of LiCl gives complexes [Mn^III(pydx-en)Cl(H₂O)] (1) [Mn^III(pydx-1,3-pn)Cl(CH₃OH)] (2) and [Mn^III(pydx-1,2-pn)Cl(H₂O)] (3), respectively. Crystal and molecular structures of [Mn(pydx-en)Cl(H₂O)] (1) and [Mn(pydx-1,3-pn)Cl(CH₃OH)] (2) confirm their octahedral geometry and the coordination of ligands through ONNO(2-) form. Reaction of manganese(II)-exchanged zeolite-Y with these ligands in refluxing methanol followed by aerial oxidation in the presence of NaCl leads to the formation of the corresponding zeolite-Y encapsulated complexes, abbreviated herein as [Mn^III(pydx-en)]-Y (4), [Mn^III(pydx-1,3-pn)]-Y (5) and [Mn^III(pydx-1,2-pn)]-Y (6). These encapsulated complexes are used as catalysts for the oxidation, by H₂O₂, of methyl phenyl sulfide, styrene and benzoin efficiently. Oxidation of methyl phenyl sulfide under the optimized reaction conditions gave ca. 86% conversion with two major products methyl phenyl sulfoxide and methyl phenyl sulfone in the ca. 70% and 30% selectivity, respectively. Oxidation of styrene catalyzed by these complexes gave at least five products namely styrene oxide, benzaldehyde, benzoic acid, 1-phenylethane-1,2-diol and phenylacetaldehyde with a maximum of 76.9% conversion of styrene by 4, 76.3% by 5 and 76.0% by 6 under optimized conditions. The selectivity of the obtained products followed the order: benzaldehyde > benzoic acid > styrene oxide > phenylacetaldehyde > 1-phenylethane-1,2-diol. Similarly, ca. 93% conversion of benzoin was obtained by these catalysts, where the selectivity of the products followed the order benzil > benzoic acid > benzaldehyde-dimethylacetal. Tests for the recyclability and heterogeneity of the reactions have also been carried. Neat complexes are equally active. However, the recycle ability of encapsulated complexes makes them better over neat ones.     

Encapsulation of tetraazamacrocyclic complexes of cobalt(II), copper(II) and oxovanadium(IV) in zeolite-Y and their use as catalysts for the oxidation of styrene

Encapsulation of tetraazamacrocyclic complexes of Co(II), Cu(II) and V(IV) into zeolite-Y has been accomplished, and the resulting materials were used as heterogeneous catalysts for aerobic oxidation of styrene. The materials were prepared by a ship-in-a-bottle method, in which the transition metal cations were first ion-exchanged into zeolite-Y and then reacted with ethylenediamine, followed by acetylacetone. The pure tetraazamacrocyclic complexes were characterized by FTIR, solid UV–Vis and elemental analysis. The structural integrity throughout the immobilization procedure, the successful immobilization of the macrocyclic complexes, and the loadings of metal ions and macrocyclic ligands were determined by characterization techniques such as FTIR, diffuse reflection UV–Vis, inductively coupled plasma atomic emission spectroscopy, scanning electron microscopy, TG/DTA and powder X-ray diffraction. Compared with their homogeneous analogues, the catalytic properties of the encapsulated macrocyclic complexes in the oxidation of styrene with air were investigated. The immobilized complexes proved to be active catalysts and could be reused without significant loss in activity.     

Host (nanopores of zeolite-Y)/guest (Co(II)-azamacrocyclic complexes) nanocomposite materials: synthesis,characterization and catalytic epoxidation of styrene with molecular oxygen

A series of Co(II) azamacrocyclic complexes, 12 Brunel, D, Bellocq, N, Sutra, P, Cauvel, A, Lasperas, M, Moreau, P, Di Renzo, F, Galarneau, A and Fajula, F. 1998. Coord. Chem. Rev., 178–180: 1085[Crossref], [Web of Science ®] , [Google Scholar]aneN₄, 14 De Vos, DE, Dams, M, Sels, BF and Jacobs, PA. 2002. Chem. Rev., 102: 3615[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]aneN₄, Bzo₂ 12 Brunel, D, Bellocq, N, Sutra, P, Cauvel, A, Lasperas, M, Moreau, P, Di Renzo, F, Galarneau, A and Fajula, F. 1998. Coord. Chem. Rev., 178–180: 1085[Crossref], [Web of Science ®] , [Google Scholar]aneN₄ and Bzo₂ 14 De Vos, DE, Dams, M, Sels, BF and Jacobs, PA. 2002. Chem. Rev., 102: 3615[Crossref], [PubMed], [Web of Science ®] , [Google Scholar]aneN₄, have been encapsulated in the nanocavity of zeolite-Y by a one pot template condensation reaction. Co(II) complexes with azamacrocyclic ligands were entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of [bis(diamine)cobalt(II)], [Co(N–N)₂]-NaY, in the supercages of the zeolite, and (ii) in situ condensation of the cobalt(II) precursor complex with diethyloxalate. The new host/guest nanocomposite materials (HGNM) have been characterized by FTIR, DRS and UV-Vis spectroscopic techniques, XRD and elemental analysis, as well as nitrogen adsorption. These complexes (neat and HGNM) were used for epoxidation of styrene with O₂ as oxidant in different solvents. Electronic spectra of the reaction mixture indicated oxidation proceeds through a free radical mechanism.     

Dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases encapsulated in zeolite-Y for the aerobic oxidation of styrene

A series of dioxovanadium(V) complexes of Schiff and tetrahydro-Schiff bases were encapsulated into the supercages of zeolite-Y and were characterized by X-ray diffraction, SEM, N₂ adsorption/desorption, FT-IR, UV-vis spectroscopy, ICPAES, pair distribution function (PDF) and X-ray absorption near edge structure (XANES) measurements. The encapsulation is achieved by a flexible ligand method in which the transition metal cations were first ion-exchanged into zeolite-Y and then complexed with ligands. The dioxovanadium-exchanged zeolite, dioxovanadium complexes encapsulated in zeolite-Y plus non-encapsulated homogeneous counterparts were all screened as catalysts for the aerobic oxidation of styrene under mild conditions. It was found that the encapsulated complexes showed better activity than their respective nonencapsulated counterparts in most cases. All encapsulated dioxovanadium tetrahydro-Schiff base complexes showed much higher activity in aerobic oxidation of styrene than their corresponding Schiff base complexes.     

Mn(II) and VO(IV) Schiff base complexes encapsulated in nanocavities of zeolite-Y: catalytic activity toward oxidation of alkenes and reduction of aldehydes

Oxovanadium(IV) and manganese(II) complexes of two Schiff base ligands, bis(2,4-dihydroxyacetophenone)-1,2-propandiimine (H₂L₁) and bis(2,4-dihydroxyacetophenone)-ethylenediimine (H₂L₂) were synthesized and characterized. The encapsulation of these complexes in the nanocavities of zeolite-Y was achieved by a flexible ligand method. The prepared heterogeneous catalysts have been characterized by FTIR, NMR and atomic absorption spectroscopy, X-ray diffraction patterns, scanning electron microscopy and BET. The catalytic activities of the encapsulated complexes were studied in the oxidation of alkenes with H₂O₂ and the reduction of aldehydes with NaBH₄. In most cases, the manganese (II) complexes (MnL₁-Y, MnL₂-Y) showed better activity than the oxovanadium (IV) complexes (VOL₁-Y, VOL₂-Y) in both oxidation of alkenes and reduction of aldehydes. The catalytic activity of the recovered catalysts was compared with the fresh ones.     

Synthesis and characterization of Cr-MSU-1 and its catalytic application for oxidation of styrene

Chromium-containing mesoporous silica material Cr-MSU-1 was synthesized using lauryl alcohol-polyoxyethylene (23) ether as templating agent under the neutral pH condition by two-step method. The sample was characterized by XRD, TEM, FT-IR, UV-Vis, ESR, ICP-AES and N₂ adsorption. Its catalytic performance for oxidation of styrene was studied. Effects of the solvent used, the styrene/H₂O₂ mole ratio and the reaction temperature and time on the oxidation of styrene over the Cr-MSU-1 catalyst were examined. The results indicate that Cr ions have been successfully incorporated into the framework of MSU-1 and the Cr-MSU-1 material has a uniform worm-like holes mesoporous structure. After Cr-MSU-1 is calcined, most of Cr³⁺ is oxidized to Cr⁵⁺ and Cr⁶⁺ in tetrahedral coordination and no extra-framework Cr₂O₃ is formed. The Cr-MSU-1 catalyst is highly active for the selective oxidation of styrene and the main reaction products over Cr-MSU-1 are benzaldehyde and phenylacetaldehyde. Its catalytic performance remains stable within five repeated runs and no leaching is noticed for this chromium-based catalyst.     

Synthesis, characterization and catalytic oxyfunctionalization of cyclohexene with tert-butylhydroperoxide over a manganese(II) complex covalently anchored to multi-wall carbon nanotubes (MWNTs)

The chemical modification of multi-wall carbon nanotubes (MWNTs) is an emerging area in material science. In the present study, an hydroxyl functionalized manganese(II) Schiff-base has been covalently anchored on modified MWNTs. The new modified MWNTs have been characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron (XPS), thermal analysis, UV–Vis, diffuse reflectance (DRS), FT-IR spectroscopy and elemental analysis. The results suggest that the symmetrical Schiff-base; N,N-bis(4-hydroxysalicylidene)-ethylene-1,2-diamine; H₂[(OH)₂-salen]; is a bivalent anion with tetradentate N₂O₂ donors derived from the phenolic oxygens and azomethine nitrogens. The formulae was found to be [Mn((OH)₂-salen)] for the 1:1 non-electrolytic complex. The multi-wall carbon nanotubes covalently anchored manganese(II) complex ([Mn((OH)₂-salen)]@MWNTs) catalyze the oxidation of cyclohexene with TBHP. Oxidation of cyclohexene catalyzed by this complex gave 2-cyclohexene-1-ol, 2-cyclohexene-1-one and 1-(tert-butylperoxy)-2-cyclohexene as the major products. The manganese(II) complex covalently anchored on MWNTs shows significantly higher catalytic activity than [Mn((OH)₂-salen)]. The activity of the immobilized catalyst remains nearly the same after three cycles, suggesting the true heterogeneous nature of the catalyst. This catalyst is more selective towards 2-cyclohexene-1-one.     

Synthesis,characterization and catalytic activity of peripherally tetra‐substituted Co(II) phthalocyanines for cyclohexene oxidation

New 3,3‐diphenylpropoxyphthalonitrile (5) was obtained from 3,3‐diphenylpropanol (3) and 4‐nitrophthalonitrile (4) with K₂CO₃ in DMF at 50 °C. The novel cobalt(II) phthalocyanine complexes, tetrakis‐[2‐(1,4‐dioxa‐8‐azaspiro[4.5]dec‐8‐yl)ethoxy] phthalocyaninato cobalt(II) (2) and tetrakis‐(3,3‐diphenylpropoxy)phthalocyaninato cobalt(II) (6) were prepared by the reaction of the phthalonitrile derivatives 1 and 5 with CoCl₂ by microwave irradiation in 2‐(dimethylamino)ethanol for at 175 °C, 350 W for 7 and 10 min, respectively. These new cobalt(II)phthalocyanine complexes were characterized by spectroscopic methods (IR, UV–visible and mass spectroscopy) as well as elemental analysis. Complexes 2 and 6 are employed as catalyst for the oxidation of cyclohexene using tert‐butyl hydroperoxide (TBHP), m‐chloroperoxybenzoic acid (m‐CPBA), aerobic oxygen and hydrogen peroxide (H₂O₂) as oxidant. It is observed that both complexes can selectively oxidize cyclohexene to give 2‐cyclohexene‐1‐ol as major product, and 2‐cyclohexen‐1‐one and cyclohexene oxide as minor products. TBHP was found to be the best oxidant since minimal destruction of the catalyst, higher selectivity and conversion were observed in the products. Copyright © 2012 John Wiley & Sons, Ltd.     

Synthesis,characterization, and catalytic oxidation of styrene,cyclohexene, allylbenzene,and cis-cyclooctene by recyclable polymer-grafted Schiff base complexes of vanadium(IV)

Schiff base-functionalized chloromethylated polystyrenes, PS-[Ae-Eol] (I), PS-[Hy-Eda] (II) and PS-[HyP-Eda] (III), were synthesized by reacting 2-(2-aminoethoxy)ethanol (Ae-Eol), N-(2-hydroxyethyl)ethylenediamine (Hy-Eda), and N-(2-hydroxpropyl)ethylenediamine (HyP-Eda) with oxidized chloromethylated polystyrene. Oxidized chloromethylated polystyrene (PS-CHO) was prepared by oxidation of chloromethylated polystyrene (PS) with sodium bicarbonate in DMSO. By reacting DMSO solution of [VO(acac)₂] with polymer-anchored Schiff base ligands I, II, and III, vanadium(IV) complexes PS-[V^IVO(Ae-Eol)] (1), PS-[V^IVO(Hy-Eda)] (2), and PS-[V^IVO(HyP-Eda)] (3) were prepared. Structure and bonding of I, II, and III as well as corresponding vanadium complexes 1, 2, and 3 were confirmed by FT-IR, UV–vis spectroscopy, SEM, EDX, AAS, TGA, EPR, etc. Polymer-anchored vanadium(IV) complexes 1, 2, and 3 show, efficient catalysis toward oxidation of styrene, cyclohexene, allylbenzene, and cis-cyclooctene in the presence of hydrogen peroxide. Optimized reaction conditions for the oxidation of these alkenes was achieved by changing various reaction parameters (like amount of catalyst, amount of oxidizing agent, volume of solvent, etc.). Polymer-grafted 1, 2, and 3 can be reused multiple times without depletion of their activity.     

Synthesis,characterization and catalytic oxidation of cyclohexene with molecular oxygen over host (nanopores of zeolite-Y)/guest ([Ni([R]2-N2X2)]2+ (R = H,CH3; X = NH,O, S) nanocatalyst

Nickel(II) complexes of 12-membered macrocyclic ligands with different donating atoms (N₂O₂, N₂S₂ and N₄) in the macrocyclic ring have been encapsulated in the nanocavity of zeolite-Y by the fexible-ligand method. Nickel(II) complexes with macrocyclic ligands were entrapped in the nanocavity of zeolite-Y by a two-step process in the liquid phase: (i) adsorption of precursor ligand; 1,2-di(o-aminophenyl-, amino, oxo, thio)ethane, N₂X₂; in the supercages of the Ni(II)–NaY, and (ii) in situ condensation of the Ni(II) precursor complex; [Ni(N₂X₂)]²⁺; with glyoxal or biacetyl. The new host–guest nanocatalysts (HGNM), [Ni([R]₂-N₂X₂)]²⁺–NaY (R = H, CH₃; X = NH, O, S), have been characterized by FT-IR, DRS and UV–Vis spectroscopic techniques, XRD and elemental analysis, as well as nitrogen adsorption, and were used for oxidation of cyclohexene with molecular oxygen.     

Copper(II) Schiff base complexes derived from 2,2′-dimethyl-propandiamine: Synthesis, characterization and catalytic performance in the oxidation of styrene and cyclooctene

Two new mononuclear copper(II) complexes ([CuL¹]·CHCl₃ (1) and [CuL²] (2)) have been prepared by the reaction of two ONNO type Schiff base ligands, ([bis(2-hydroxy-propiophenone)2,2′-dimethylpropan-diamine] (H₂L¹) and [bis(5-bromosalicylaldehyde)2,2′-dimethyl-propandiamine] (H₂L²)) with Cu(OAc)₂·H₂O in 1:1 molar ratios. The complexes have been characterized by elemental analyses, IR and UV-Vis spectroscopy. The structures have been confirmed by X-ray single crystal analysis at 100 K. The Cu(II) atom in 1 is coordinated equatorially by a N₂O₂ donor set of the tetradentate, dinegative Schiff-base (L¹)²⁻ in a distorted square planar arrangement. While in [CuL²] (2), the Cu(II) ion possesses an additional weak intermolecular contact with one bromine atom of the ligand, thus the coordination sphere of 2 can be described as strongly distorted square pyramidal. The catalytic performance of the prepared copper complexes for the oxidation of styrene and cyclooctene with tert-butyl hydroperoxide has been evaluated.     

Synthesis of achiral NCN pincer Pt(II) and Pd(II) complexes and catalytic application in the Suzuki-Miyaura reaction

A series of platinum and palladium pincer complexes supported by achiral 1,3-bis(2′-imidazolinyl)benzene-based NCN ligands have been prepared via direct C2 metalation. Meanwhile, ligand precursor 3b and Pt(II) complex 4b were characterized by crystallographic studies, which reveals that the platinum atom in 4b adopts a distorted-square-planar geometry. The Pd(II) pincer complexes 5b was found to be an efficient catalyst for Suzuki cross-coupling reaction of aryl bromides and phenylboronic acid under air. In the presence of 0.5?mol% of Pd(II) 5b in DMF/K₃PO₄·3H₂O for 8?h, the corresponding biaryl products could be obtained in 24–99% yields.     

Homo‐ and copolymerization of norbornene with styrene catalyzed by a series of copper(II) complexes in the presence of methylaluminoxane

Vinyl‐type polymerization of norbornene as well as random copolymerization of norbornene with styrene was studied using a series of copper complexes‐MAO. The precatalysts used here are copper complexes with β‐ketoamine ligands based on pyrazolone derivatives and the molecular structure of complex 4 was determined using X‐ray analysis. All of these catalyst systems are moderately active for the vinyl‐type polymerization of norbornene and random copolymerization of norbornene with styrene. The random copolymers obtained suggest that only one type of active species is present. Gel permeation chromatography (GPC) and NMR indicate that the copolymers are ‘true’ copolymers. The copolymerization reactivity ratios (r_NBE = 20.11 and r_Sty = 0.035) indicate a much higher reactivity of norbornene, which suggests a coordination polymerization mechanism. The solubility and processability of the copolymers are improved relative to polynorbornene and the thermostability of the copolymers is improved relative to polystyrene. Copyright © 2006 John Wiley & Sons, Ltd.