Showing papers in "Transition Metal Chemistry in 2007"

Synthesis and characterization of complexes of Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) with macrocycle 3,4,11,12-tetraoxo-1,2,5,6,9,10,13,14-octaaza-cyclohexadeca-6,8,14,16-tetraene and their biological screening

Abstract: A new series of complexes is synthesized by template condensation of glyoxal and oxalyldihydrazide in methanolic medium in the presence of divalent cobalt, nickel, copper, zinc and cadmium salts forming complexes of the type: [M(C8H8N8O4)X2] where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and X = Cl−1, Br−1, NO 3 −1 , OAc−1. The complexes have been characterized with the help of elemental analyses, conductance measurements, magnetic susceptibility measurements, electronic, n.m.r., infrared and far infrared spectral studies. On the basis of these studies, a six coordinate octahedral geometry for these complexes has been proposed. The biological activities of the metal complexes have been tested in vitro against a number of pathogenic bacteria to assess their inhibiting potential. Most of the compounds have been found to exhibit remarkable antibacterial activities.

Synthesis, spectroscopic investigation and biological activity of metal complexes with ONO trifunctionalalized hydrazone ligand

Abstract: MnII, FeIII, CoII, NiII, CuII, ZnII, LaIII, RuIII, HfIV, ZrIV and UVI complexes of 4-methylphenylamino acetoacetylacetone hydrazone have been synthesized and characterized by elementals analyses, i.r., u.v.–vis. spectra, magnetic moments, conductances, thermal analyses (d.t.a and t.g.a) and e.s.r measurements. The i.r. data show that, the ligand behaves as a neutral bidentate type (10), (13) and neutral tridentate type (4), (11), (12) and (21) monobasic bidentate type (7) or monobasic tridentate type (2), (3), (5), (6), (8), (14), (15), (16), (18), (19), (20) and (22) or dibasic tridentate type (5), (9) and (17) towards the metal ion. Molar conductances in DMF solution indicate that, the complexes are non-electrolytes. The e.s.r spectra of solid complexes (8) and (10) show axial type spectra with $${\hbox{g}_{\|} > \hbox{g}_{\bot} > 2.0023}$$ , d(x2-y2) ground state with significant covalent bond character. However, complex (12), shows an isotropic type, indicating a octahedral manganese(II) complex. Antibacterial and antifungal tests of the ligand and some of its metal complexes are also carried out and it has been observed that, the complexes are more potent bactericides and fungicides than the ligand.

Synthesis, characterization and biological studies of CoII, NiII, CuII and ZnII complexes of Schiff bases derived from 4-substituted carbostyrils[quinolin2(1H)-ones]

Abstract: Schiff bases derived from 4-aminomethylcarbostyril and their transition metal complexes with CoII, NiII, CuII and ZnII have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibilities electronic, IR, PMR, ESR, FAB-Mass and thermal studies. From the above spectral studies it is concluded that the ligands of 4-substituted carbostyril Schiff bases, viz, salicylidene 4-aminomethylcarbostyril (SAMC); o-vanillinsalicylidene 4-aminomethylcarbostyril (VAMC) and 5′ chlorosalicylidene 4-aminomethylcarbostyril (CSAMC) act as bidenate molecules coordinating through azomethine nitrogen and phenolic oxygen. The ligands and their metal complexes have been screened in vitro for antibacterial, antifungal and antitumor activity. The results indicate that the biological activity increases on complexation. The CuII complexes of the above ligands show greater inhibitory action towards the P388/s tumor cells at lower concentrations.

Synthesis and spectroscopic studies of new binuclear transition metal complexes of Schiff bases derived from 4,6-diacetylresorcinol

Abstract: Two new series of copper(II), nickel(II), cobalt(II), zinc(II), iron(III), chromium(III), vanadyl(IV) and uranyl(VI) complexes with two bifunctional tridentate Schiff base, H4L1 and H2L2 ligands have been prepared. The Schiff base, H4L1 and H2L2, ligands were synthesized by the condensation of 4,6-diacetylresorcinol with o-aminophenol or o-phenylenediamine. The ligands are either di- or tetra-basic with two symmetrical sets of either OON or NNO tridentate chelating sites. The ligands and their metal complexes have been characterized by elemental analysis, 1H-n.m.r., FT-IR, mass, electronic, esr spectra and thermal gravimetric analysis and magnetic susceptibility. With the exception of CoII ion with H2L2 which afforded a trinuclear complex, a variety of binuclear complexes for the rest of the metal complexes were obtained with the ligands in its di- or tetra-deprotonated forms. The bonding sites are the azomethine and amino nitrogen atoms, and phenolic oxygen atoms. The metal complexes exhibit different geometrical arrangements such as square planar, tetrahedral, square pyramid and octahedral arrangement.

Cobalt(II) complexes of various thiosemicarbazones of 4-aminoantipyrine: syntheses, spectral, thermal and antimicrobial studies

Abstract: An interesting series of cobalt(II) complexes of the new ligands: 4[N-(benzalidene)amino]antipyrinethiosemicarbazone (BAAPTS), 4[N-(2′-hydroxy-benzalidene)amino]antipyrinethiosemicarbazone (HBAAPTS) and 4[N-(2′-hydroxy-1′-naphthalidene)amino]antipyrinethiosemicarbazone (HNAAPTS) were synthesized by reaction with Co(II) salts in ethanol The general stoichiometry of the complexes was found to be [CoX2(H2O)(L)] and [Co(L)2](ClO4)2, where X = Cl, NO3, NCS or CH3COO and L = BAAPTS, HBAAPTS or HNAAPTS The complexes were characterized by elemental analysis, molar conductivity measurement, molecular weight determination, magnetic moments at room temperature, infrared and electronic spectra All the thiosemicarbazones behave as neutral tridentate (N, N, S) donor ligands The conductivity measurements in PhNO2 solution indicated that the chloro, nitrato, thiocyanato and acetate complexes are essentially non-electrolytes, while the perchlorate complexes are 1:2 electrolytes Thermogravimetric studies were performed for some representative complexes and the decomposition mechanism proposed Antibacterial and antifungal properties of the ligands and their cobalt(II) complexes have also been examined and it has been observed that the complexes are more potent bactericides than the ligand

Mixed ligand complexes with 2-piperidine-carboxylic acid as primary ligand and ethylene diamine, 2,2′-bipyridyl, 1,10-phenanthroline and 2(2′-pyridyl)quinoxaline as secondary ligands: preparation, characterization and biological activity

Abstract: Synthesis procedures are described for the new stable mixed ligand complexes, [Pd(Hpa)(pa)]Cl, [Pd(pa)(H2O)2]Cl, [Pd(pa)(en)]Cl, [Pd(pa)(bpy)]Cl, [Pd(pa)(phen)Cl], [Pd(pa)(pyq)Cl], cis-[MoO2(pa)2], [Ag(pa)(bpy)], [Ag(pa)(pyq)], trans-[UO2(pa)(pyq)](BPh4) and [ReO(PPh3)(pa)2]Cl (Hpa = 2-piperidine-carboxylic acid, en = ethylene diamine, bpy = 2,2′-bipyridyl, phen = 1,10-phenanthroline, pyq = 2(2′-pyridyl)quinoxaline). Their elemental analyses, conductance, thermal measurements, Raman, IR, electronic, 1H-n.m.r. and mass spectra have been measured and discussed. 2-Piperidine-carboxylic acid and its palladium complexes have been tested as growth inhibitors against Ehrlich ascites tumour cells (EAC) in Swiss albino mice.

Electrocatalytic activity of binary Palladium Ruthenium anode catalyst on Ni-support for ethanol alkaline fuel cells

Abstract: In search for a cheaper anode catalyst for the oxidation of ethanol for development of direct alcohol fuel cells, Pd has been considered here as an interesting substitute for Pt in Pt Ru binary electrodeposite. The binary catalyst when co-deposited on nickel support has been found to increase the current density and decrease the anodic overvoltage significantly with respect to pure Pt, Pd and Ni. Its electrocatalytic capability is also comparable with that of the Pt-Ru binary electrocatalyst on Ni-support, when studied in 1 M EtOH containing 1 M NaOH solution. The effect of loading of Pd Ru electrocatalyst on Ni support has also been tested. The electrocatalytic activity of the electrodes for oxidation of ethanol has been explained by studies of cyclic voltammetry, chronopotentiometry, steady-state polarization, and conjugated scanning electron microscopy–energy dispersion X-ray spectroscopy. It has been found that electrode containing the higher amount of deposit are less affected by carbonaceous poisons.

Complexes of iron(III) salen and saloph Schiff bases with bridging 2,4,6- tris (2,5-dicarboxyphenylimino-4-formylphenoxy)-1,3,5-triazine and 2,4,6- tris (4-carboxyphenylimino-4′-formylphenoxy)-1,3,5-triazine

Abstract: Four new trinuclear Fe(III) complexes involving tetradenta Schiff bases N,N1-bis(salicylidene) ethylenediamine-(salenH2) or bis(salicylidene)-o-phenylenediamine-(salophH2) with 2,4,6-tris(2,5-dicarboxyphenylimino-4-formylphenoxy)-1,3,5-triazine (DCPI-TRIPOD) or 2,4,6-tris(4-carboxyphenylimino-4′-formylphenoxy)-1,3,5-triazine (CPI-TRIPOD) have been synthesized and characterized by means of elemental analysis carrying out 1H-n.m.r., i.r. spectroscopy, thermal analyses and magnetic susceptibility measurements. The complexes can also be characterized as high-spin distorted octahedral FeIII bridged by carboxylic acids. The tricarboxylic acids play a role as bridges for weak antiferromagnetic intramolecular exchange.

Modern spectroscopic and biological approach in the characterization of a novel 14-membered [N4] macrocyclic ligand and its transition metal complexes

Abstract: A novel tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 1,3,4,8,9,11-hexaaza-2,5,10,12-tetraoxo-7,14-diphenyl-cyclotetradecane (L), has been synthesized. Mn(II), Co(II), Ni(II) and Cu(II) complexes of this ligand have been prepared and subjected to elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, 1H-n.m.r. (Ligand), i.r., electronic, and e.p.r. spectral studies. On the basis of molar conductance the Mn(II), Co(II) and Cu(II) complexes may be formulated as [M(L)X2] [where X = Cl− & NO3−] due to their non-electrolytic nature in dimethylformamide (DMF). Whereas the Ni(II) complexes are 1:2 electrolytes and formulated as [Ni(L)]X2. All the complexes are of the high spin type and are six/four coordinate. On the basis of i.r., electronic and e.p.r. spectral studies an octahedral geometry has been assigned to Mn(II) and Co(II), square planar for Ni(II) complexes, and tetragonal for Cu(II) complexes. The antimicrobial activities of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against several species of bacteria and plant pathogenic fungi.

Synthesis, characterization and redox properties of macrocyclic Schiff base by reaction of 2,6-diaminopyridine and 1,3-bis(2-carboxyaldehyde phenoxy)propane and its CuII, NiII, PbII, CoIII and LaIII complexes

Abstract: A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:,14,15-tribenzo-9,13-dioxacyclohexadeca-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine and 1,3-bis(2-carboxyaldehyde phenoxy)propane. Then, its CuII, NiII, PbII, CoIII and LaIII complexes were synthesized by a template effect by reaction of 2,6-diaminopyridine and 1,3-bis (2-carboxyaldehyde phenoxy)propane and Cu\({(\hbox{NO}_{3})_{2} \cdot 3\hbox{H}_{2}}\)O, Ni\({(\hbox{NO}_{3})_{2} \cdot 6\hbox{H}_{2}}\)O, Co\({(\hbox{NO}_{3})_{2} \cdot 6\hbox{H}_{2}}\)O, La\({(\hbox{NO}_{3})_{3} \cdot 6\hbox{H}_{2}}\)O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, 1H- and 13C-NMR-, UV-vis spectra, magnetic susceptibility, conductivity measurements, mass spectra and cyclic voltammetry. All complexes are diamagnetic and the CuII complex is binuclear. The diamagnetic behaviour of the binuclear complex may be explained by a very strong anti-ferromagnetic interaction in the Cu–Cu pair. The CoII was oxidised to CoIII.

Synthesis and spectral characterization of macrocyclic NiII complexes derived from various diamines, NiII perchlorate and 1,4-bis(2-carboxyaldehydephenoxy)butane

Abstract: Six new macrocyclic complexes were synthesized by reaction of 1,4-bis(2-carboxyaldehyde phenoxy)butane with various diamines. Then, their nickel(II) perchlorate complexes were synthesized by the template effect by reaction of 1,4-bis(2-carboxyaldehyde phenoxy)butane, Ni(ClO4)2 · 6H2O and various diamines. The metal-to-ligand ratio of NiII metal complexes was found to be 1:1. The compounds are coordinated to the central metal as tetradentate O2N2 ligands The NiII complexes are proposed to exhibit tetrahedral geometry. NiII metal complexes are 1:2 electrolytes as shown by their molar conductivities (ΛM) in DMF (dimethyl formamide) at 10−3 m. The structure of NiII metal complexes is proposed from elemental analysis, f.t.-i.r., u.v.-vis., magnetic susceptibility measurements, molar conductivity measurements and mass spectra.

Synthesis and spectral characterization of zinc(II), copper(II), nickel(II) and manganese(II) complexes derived from bis (2-hydroxy-1-naphthaldehyde) malonoyldihydrazone

Abstract: The present study shows that the reaction of different salts of the same metal with sterically crowded dihydrazone bis(2-hydroxy-1-naphthaldehyde)malonoyldihydrazone (CH2LH4) in ethanol/aqueous media gives complexes of different stereochemistry. While the reaction of zinc(II) and copper(II) sulphate with dihydrazone yields tetrahedral complexes, the zinc(II) and copper(II) chlorides give square pyramidal and distorted octahedral complexes, respectively. On the other hand, nickel(II) sulphate and chloride, both give high-spin octahedral complexes with dihydrazone, manganese sulphate gives low-spin octahedral and manganese(II) chloride gives high-spin octahedral complexes. The reaction of these complexes with KF has been investigated. All of the products have been characterized by analytical, magnetic moment and molar conductivity data. The structures of the complexes have been established by spectroscopic studies.

Synthesis and spectroscopic characterization of transition metal complexes of a 12-membered tetraaza [N4] macrocyclic ligand and their biological activity

Abstract: Cobalt(II), nickel(II) and copper(II) complexes are synthesized with 1,3,7,9-tetraaza- 4,6,10,12-tetraphenyl-2,8-dithiacyclododecane, a tetradentate ligand (L) and characterized by elemental analysis, molar conductance measurements, magnetic susceptibitity measurements, mass, i.r., electronic and e.p.r. spectral studies. All the complexes are non-electrolytes so they may be formulated as [M(L)X2] [where, M = Co(II), Ni(II) and Cu(II) and X = Cl− and NO3−]. All the complexes are of high spin type. On the basis of i.r., electronic and e.p.r. spectral studies an octahedral geometry has been assigned for Co(II) and Ni(II) complexes and tetragonal geometry for Cu(II) complexes. The antimicrobial activities of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against two different species of bacteria and plant pathogenic fungi.

Studies on bismuth(III) complexes of ligands containing nitrogen/sulfur and extractive procedure for determination of Bi(III)

Abstract: The coordination behavior of thiosemicarbazide and its thiosemicarbazones towards Bi(III) is the main goal of this investigation. The structure of the isolated complexes has been proved by microanalysis, thermal, spectra (electronic, IR and ms) and voltammetric measurements. The ligands act as neutral or mononegative molecules and the coordination donors were found to be S for HTS; NN for HBTS; NS for HATS and H2STS and NNS or NSO for H2DMTS in the complexes. The complexes show thermal decomposition steps ending at 800 °C with a stable fragment. The redox properties of the complexes toward oxidation waves are strongly dependent on = Nthio substituents. At pH 1.5 and excess of iodide, Bi3+ forms an orange–yellow [BiI4]− complex which associated with tricaprylylmethylammonium chloride (TCMAC) forming [TCMA]+[BiI4]− easily extracted into the CHCl3 layer. The colored organic layer containing the ion pair is determined spectrophotometrically at 490 nm and represents the second goal.

Synthesis and spectral characterization of macrocyclic Schiff base by reaction of 2,6-diaminopyridine and 1,4-bis(2-carboxyaldehydephenoxy)butane and its CuII, NiII, PbII, CoIII and LaIII complexes

Abstract: A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:15,16-tribenzo-9,15-dioxacycloheptadeca-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine with 1,4-bis(2-carboxyaldehydephenoxy)butane. Then, its CuII, NiII, PbII, CoIII and LaIII complexes were synthesized by the template effect by reaction of 2,6-diaminopyridine and 1,4-bis (2-carboxyaldehydephenoxy)butane and Cu(NO3)2 · 3H2O, Ni(NO3)2 · 6H2O, Pb(NO3)2, Co(NO3)2 · 6H2O, La (NO3)3 · 6H2O, respectively. The ligand and its metal complexes were characterized by elemental analysis, IR, 1H- and 13C-n.m.r., UV-vis spectra, magnetic susceptibility, thermal gravimetric analysis, conductivity measurements and mass spectra. All complexes are diamagnetic and the CuII complex is binuclear. The CoII complex was oxidised to CoIII.

Synthesis spectroscopic and biological approach in the characterization of novel [N4] macrocyclic ligand and its transition metal complexes

Abstract: A novel tetradentate nitrogen donor [N4] macrocyclic ligand, i.e. 1,3,4,8,9,11-hexaaza-2,10-dithia-5,12-dioxo-7,14-diphenyl-cyclotetradecane (L), has been synthesized. Manganese(II),cobalt(II), nickel(II) and copper(II) complexes with this ligand have been prepared and subjected to elemental analyses, molar conductance measurements, magnetic susceptibility measurements, mass, 1H-n.m.r. (Ligand), i.r., electronic, and e.p.r. spectral studies. On the basis of molar conductance the complexes may be formulated as [M(L)X2] [where M = MnII, CoII, NiII, and CoII,and X = Cl− & NO3−] due to their nonelectrolytic nature in dimethylformamide (DMF). All the complexes are of the high spin type and are six coordinated. On the basis of i.r., electronic and e.p.r. spectral studies an octahedral geometry has been assigned to MnII, and II, II, complexes, and tetragonal for copper(II) complexes. The antimicrobial activities of the ligand and its complexes, as growth inhibiting agents, have been screened in vitro against several species of bacteria and plant pathogenic fungi.

Synthesis and characterization of a new macrocyclic Schiff base derived from 2,6-diaminopyridine and 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane and its Cu(II), Ni(II), Pb(II), Co(III) and La(III) complexes

Abstract: A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:19,20-tribenzo-9,12,15,18-tetraoxacyclounkosa-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine and 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane. Then, its CuII, NiII, PbII, CoIII and LaIII complexes were synthesized by the template effect by reaction of 2,6-diaminopyridine and 1,10-bis(2-formylphenyl)-1,4,7,10-tetraoxadecane and Cu(NO3)2· 3H2O, Ni(NO3)2· 6H2O, Pb(NO3)2, Co(NO3)2· 6H2O, La(NO3)3·6H2O respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, 1H and 13C NMR, u.v–vis spectra, magnetic susceptibility, conductivity measurements and mass spectra. All complexes are diamagnetic and the CuII complex is binuclear. The CoIII complex was oxidized to CoIII.

Spectroscopic studies of bridged binuclear complexes of Co(II), Ni(II), Cu(II) and Zn(II)

Abstract: Binuclear cobalt(II), nickel(II), copper(II) and zinc(II) complexes of general composition [M2L1-2(μ-Cl)Cl2] · nH2O with the Schiff-base ligands (where L1H and L2H are the potential pentadentate ligands derived by condensing 2,6-diformyl-4-methylphenol with 4-amino-3-antipyrine and 2-hydroxy-3-hydrazinoquinoxiline, respectively) have been synthesized and characterized. Analytical and spectral studies support the above formulation. 1H-NMR and IR spectra of the complexes suggest they have an endogenous phenoxide bridge, with chloride as the exogenous bridge atom. The electronic spectra of all the complexes are well characterized by broad d–d and a high intensity charge-transfer transitions. The complexes are chloro-bridged as evidenced by two intense far-IR bands centered around 270–280 cm−1. Magnetic susceptibility measurements show that complexes are antiferromagnetic in nature. The compounds show significant growth inhibitory activity against fungi Aspergillus niger and Candida albicans and moderate activity against bacteria Bacillus cirroflagellosus and Pseudomonas auresenosa.

Spectral and electrochemical characterization of bimetallic complexes of a novel 32-membered unsymmetrical (N 12 ) macrocycle

Abstract: Reactions of a 32-membered [N12] macrocyclic ligand, L.2HClO4 with metal salts MCl3 (M=Cr or Fe) and MCl2 (M=Co, Ni or Cu) have produced complexes of stoichiometries M2LCl4(ClO4)2 and M2LCl2(ClO4)2, respectively. However, reactions with [M(Ph3P)2Cl2] (M=Co or Ni) and [(η5-C5H5)Ni(Ph3P)I] follow a ligand substitution path resulting in products with stoichiometries M2LCl2(ClO4)2 and [(η5-C5H5)2Ni2L(ClO4)2], respectively. The mode of bonding and geometry of the complexes have been derived on the basis of i.r., ligand field spectral and magnetic susceptibility measurements. EPR of CuII complex shows anisotropy with \(\hbox{g}_{||} > \hbox{g}_{\bot}> 2.0\), G \hbox{K}_{||}(0.853)\). Thermodynamic first ionic association constants (K1) and the corresponding free energy change (ΔG) of complexes in DMSO have been determined and discussed. Cyclic voltammetric studies indicate the presence of a quasi-reversible redox couples CrIII/II, CoII/I, NiII/I, NiII/III and CuII/I in solutions suggesting flexible nature of the macrocyclic cavity.

Synthesis and spectral characterization of some new azo dyes and their metal complexes

Abstract: A series of azo-metal chelate dyes have been synthesized by coupling substituted o-nitroaniline and p-t-/s-butylphenol The spectral characterization of the azo dyes containing o-hydroxy group and azo-metal(II) chelate [metal(II): Cu, Ni, Co] dyes by IR spectra, UV–VIS spectra, NMR spectra, elemental analysis and magnetic susceptibility techniques are reported The stoichiometry of the azo-metal chelates was determined by the spectroscopic titration method to be 1:2 (ML2)

Synthesis, spectral characterization, catalytic and antibacterial activity of macrocyclic CuII compounds

Abstract: Macrocyclic CuII compounds of the type Cu(L4)Cl2 (where L4 = N4 or N2O2 donor macrocyclic ligand) have been synthesized by treating the corresponding macrocycles with copper chloride in methanol. These compounds were characterized with the help of elemental analysis, i.r., mass, ESR, electronic spectra, conductance, magnetic and thermal studies. Distorted octahedral geometry has been proposed for all of these compounds. These compounds were found to be efficient in the catalytic oxidation of ascorbic acid and the percentage yields of oxidation products were determined spectrophotometrically. The biological activities of these compounds have been tested against gram +ve and gram −ve bacteria and found to be more active when compared with commercially available antibacterials like streptomycin and ampicillin.

Transition metal catalysts

Abstract: Transition metal catalysts comprise (a) a source of a Group 3 to 10 transition metal, (b) a ligand having the formula: R1R2X-Y-XR3R4 wherein X is phosphorus, arsenic or antimony, Y is a bridging group having the formula: Z-(A)-D-Rm wherein Z is the moiety linking the X groups, A is a linear or cyclic hydrocarbyl, substituted hydrocarbyl, heterohydrocarbyl or substituted heterohydrocarbyl linking group wherein the number of atoms directly linking Z to D is 1, 2 or 3, D is N, P, As, O, S or Se, R is hydrogen, alkyl, hydrocarbyl, substituted hydrocarbyl, heteroalkyl, heterohydrocarbyl or substituted heterohydrocarbyl, and m is 1 or 2, R1,R2,R3, and R4 are the same or different and represent hydrocarbyl or functionalized hydrocarbyl moieties with the proviso that if D is nitrogen, R is not a cyclic ether, and optionally an activator. The transition metal catalysts are suitable for the selective trimerisation or tetramerisation of olefins in particular ethylene.

Mechanistic study of iodide catalysed oxidation of l -glutamic acid by cerium(IV) in aqueous sulphuric acid medium

Abstract: A minute quantity (10−6 mol dm−3) of iodide catalysed oxidation of l-glutamic acid by CeIV has been studied in H2SO4 and SO 4 2− media. The reaction was first order each in [CeIV] and [I−]. The order with respect to [l-glutamic acid] was less than unity (0.71). Increase in [H2SO4] decreased the reaction rate. The added HSO 4 − and SO 4 2− decreased the rate of reaction. The added product, succinic acid, had no effect on the reaction rate, whereas added CeIII retarded the reaction. The ionic strength and dielectric constant did not have any significant effect on the rate of reaction. The active species of oxidant was Ce(SO4)2. A suitable mechanism was proposed. The activation parameters were determined with respect to the slow step of the mechanism. The thermodynamic quantities were also determined and discussed.

Bis (macrocyclic)dinickel(II) complexes containing phenylene bridges between 13-membered triaza dioxa macrocyclic ligands: in-situ one pot template synthesis, characterization and catalytic oxidation of cyclohexene

Abstract: A new series of bis(macrocyclic)dinickel(II) complexes containing phenylene bridges between 13-membered triaza dioxa macrocyclic subunits have been synthesized via in-situ One Pot Template Condensation (IOPTC) of nitrogen–nitrogen linker, CH2O and 1,8-diamino-3,6-dioxaoctane and nickel(II) in a 1:4:2:2 molar ratio. These complexes have been found to be effective catalysts for the selective oxidation of cyclohexene to 2-cyclohexene-1-one and 2-cyclohexene-2-ol with molecular oxygen as the oxidant.

Chelates and corrosion inhibition of newly synthesized Schiff bases derived from o -tolidine

Abstract: New copper(II), nickel(II), iron(III) and palladium(II) Schiff base complexes derived from o-tolidine and selected aldehydes, namely salicyaldehyde and 2-hydroxynaphthaldehyde have been synthesized and characterized by a combination of elemental analyses, magnetic moments, spectral (u.v.–vis., i.r.) and thermal (tg, dtg) mesurements. The corrosion inhibition of aluminium and copper in 1 M HCl and chromium–nickel steel in crude oil using N,N′bis(salicyledene)-o-tolidine have been studied by weight loss method.

Spectral and biological investigation of 5-hydroxyl-3-oxopyrazoline 1-carbothiohydrazide and its transition metal complexes

Abstract: Mononuclear complexes of 5-hydroxyl-3-oxopyrazoline-1-carbothiohydrazide, H3HOC, with VO2+, Co(II), Ni(II), Cu(II) and Cd(II) have been isolated. The elemental analyses, magnetic, spectral [u.v.–vis., i.r., e.s.r. 1H n.m.r. and mass] with thermal analysis have been used to characterize the isolated complexes. The ligand behaves as a mononegative tridentate with Ni(II) and Co(II) ions and neutral bidentate in [Cu(H3HOC)(NO3)2]0.5 H2O, [VO(H3HOC)SO4] and [Cd(H3HOC)Cl2C2H5OH]C2H5OH complexes. The octahedral structure was suggested for all the isolated complexes except VO2+. The TG analyses recorded different decomposition steps started at a temperature, indicating thermally unstable complexes. Screening showed antimicrobial activity for Cd(II) and Ni(II) complexes against the investigated bacteria as well as a significant adverse effects on DNA but a moderate effect is displayed with the other complexes.

Synthesis, properties, and catecholase-like activity of the [1,4-di(6′-methyl-2′-pyridyl)aminophthalazine]dimanganese(II) complex, Mn2(6′Me2PAP)2Cl4

Abstract: The preparation, spectroscopic properties, and catecholase-like activity of the dimanganese(II) complex [Mn2(6′Me2PAP)2Cl4] [6′Me2PAP: 1,4-di(6′-methyl-2′-pyridyl)aminophthalazine] are reported. The title compound was suitable catalyst for the oxidation of 3,5-di-t-butylcatechol (3,5-DTBCH2) to 3,5-di-t-butyl-1,2-benzoquinone (3,5-DTBQ) with dioxygen under ambient conditions in good yields. The catalytic oxidation was found to obey Michaelis–Menten type kinetics.

Synthesis and reactivity of N,N-bis (diphenylphosphino)dimethylaniline compounds

Abstract: New chalcogenides and complexes of N,N-bis(diphenylphosphino)dimethylanilines were prepared by the reaction of N,N-bis(diphenylphosphino)dimethylaniline ligands with aqueous H2O2, elemental S and Se and transition metal complexes based on Cu, Pd and Pt. All the new compounds have been characterised by spectroscopy and the molecular structures of the three complexes of N,N-bis(diphenylphosphino)dimethylanilines have been determined by X-ray crystallography.

Copper(II) complexes of pyrrolidine dithiocarbamate

Abstract: Copper(II)-pyrrolidine dithiocarbamate (PDTC) complexes having the general formula, [Cu(PDTC)2], [Cu(PDTC)X2]− (where X = Cl−, I−, CN−, SCN−) and [Cu(PDTC)(en)]+ (en = ethylenediamine) have been prepared and characterized by IR spectroscopy and by thermogravimetric analysis (TGA and DTA). The IR data suggests that coordination of pyrrolidine dithiocarbamate (PDTC) takes place through the two sulphur atoms in a symmetrical bidentate fashion. The results of thermal analysis are consistent with the proposed composition of the complexes.

Ruthenium(III) – catalyzed oxidative cleavage of p-aminoazobenzene by chloramine-B in alkaline medium and uncatalyzed reaction in acid medium: spectrophotometric kinetic and mechanistic study

Abstract: p-Aminoazobenzene (PAAB) is one of the important monoazo dyes and its oxidation kinetic study is of much use in understanding the mechanistic profile of PAAB in redox reactions. Consequently, the kinetics of oxidation of PAAB by sodium N-chlorobenzenesulfonamide or chloramine-B (CAB) in HClO4 medium and in NaOH medium catalyzed by ruthenium(III) chloride (RuIII) have been investigated at 298 K. U.v.–vis spectrophotometry was used as a basic analytical approach in this study. Under an identical set of experimental conditions, the reactions of PAAB–CAB in HClO4 medium were facile, but the reactions became too slow to be studied in alkaline medium and hence ruthenium(III) chloride has been used as a catalyst in alkaline medium. The stoichiometry (1:2) and oxidation products (nitrosobenzene and p-nitrosoaniline) are the same in both media, but the kinetic and mechanistic patterns were found to be different. The experimental rate laws obtained are: − d[CAB]/dt = k [CAB]0 [PAAB]0 [H+] in acid medium and − d[CAB]0/dt = k [CAB]0 [PAAB]0[OH−]x[RuIII]y in alkaline medium, where x and y are less than unity. The reaction was examined with reference to changes in (a) concentration of benzenesulfonamide, (b) concentration of added neutral salts, (c) ionic strength, (d) dielectric permitivity and (e) solvent isotope effect. The reaction was also studied at different temperatures and the overall activation parameters have been evaluated. The oxidation reaction fails to induce the polymerization of added acrylonitrile. C6H4SO2NHCl and C6H4SO2NCl− have been postulated as the reactive oxidizing species in acidic and alkaline media, respectively. It was found that the reactions are nearly 20 times faster in acid medium in comparison with alkaline medium. It was also observed that ruthenium(III) was an efficient catalyst for the facile oxidation of PAAB by CAB in alkaline medium by making the reaction go twelve-fold faster than the uncatalyzed reactions. The catalytic constant (KC) has been calculated at different temperatures and the values of activation parameters with respect to ruthenium(III) have also been evaluated in alkaline medium. The observed results have been explained by plausible mechanisms and the relative rate laws have been deduced.