Condensation of β,δ-triketone derived from dehydroacetic acid with aliphatic amines and copper(II) complexes of the schiff bases

The condensation of ethyl-2-hydroxy-4-oxo-4-(4-hydroxy-6-methyl-2-pyrone-3-yl)-2-butenoate with primary aliphatic monoamines occurs at 4-hydroxy group of the pyrone ring according to ¹HNMR and mass spectrometric data. The ketamine tautomeric form of the prepared Schiff bases is predominantly present in chloroform solutions. Isolated crude copper(II) complexes of the condensation products are shown to be mononuclear with the 1:2 metal to ligand ratio.     

Transition metal complexes of the schiff base derivatives of the ligand 1,8-dihydroxy-3,6-dimethyl-2-acetylnaphthalene

New Schiff bases derived from 2-acetyl-1,8-dihydroxy-3,6-dimethylnaphthalene(H₂addn) and 1,2-propanediamine(pn), 2,3-butanediamine(pn) and 1,2-cyclohexyldiamine(chn) have been prepared and characterized as (H₄addn-diam). In this work is reported an improved experimental method which yields well characterized mononuclear species of H₄addn-en and H₄addn-pn with Cu(II), Ni(II) and Co(II). The Cu(II) complex has been studied by esr which unambigously shows a N₂O₂ coordination mode for the metal ion. Based on the spectral characteristics of these complexes we conclude that all metal atoms have the same coordination mode. Only one binulear complex, [NiUO₂(addn-en)] is reported in this work. All attempts to synthesize binuclear complexes with first transition series metal ions were unsuccessful.     

Esca studies on the structure of amorphous addition complexes of tin dichloride with aromatic schiff bases

The ESCA characterization of three similar new amorphous addition complexes of tin dichloride with tetradentate aromatic Schiff bases has been carried out. The results support the previously proposed ionic structure.     

Transition metal complexes with 1-methyl-4,4-dimercaptopiperidine

The syntheses of Co(AH₂)₂X₂ (AH₂ = 1-methyl-4, 4-dimercaptopiperidine, X = Cl Br, I, acetate, propanate, perchlorate, nitrate and sulphate), M(AH₂) Cl₂ (M = Cd, Zn) are described. According to IR and UV-visible data it seems most probable that the aminogem-dithiol (AH₂) coordinates Co via both sulphur atoms, but Zn and Cd via one sulphur. A square pyramidal geometry about Co and a tetrahedral geometry about Zn and Cd are proposed. In no case has coordination via nitrogen been found. Strong X-H…N hydrogen bonds have been observed in most of these complexes.     

Preparation and characterization of copper(II) and nickel(II) complexes with novel tetraaza-macrocyclic schiff bases

Novel tetraaza-macrocycles with N-substituted carbamoyl groups were prepared by the reaction of 5,7,12,14-tetramethyl-1,4,8,11-tetraazacyclotetradeca-1,5,7,12-tetraene with isocyanates (RNCO, R = Ch₃ and C₆H₅). Their copper(II) and nickel(II) complexes were characterized by magnetic susceptibilities, electronic absorption spectra, and electrochemical properties. The complexing abilities and extractabilities of the ligands for the metal ions were investigated.     

Transition metal complexes of hydrotris(imidazolyl)borate anion

The preparation and characterization of the ligand potassium hydrotris(imidazolyl)borate and some of its complexes with transition metals is reported. These complexes have apparently an octahedral structure except the Cu(II) complex which seems to have a square planar geometry. The values of the ligand field parameters 10Dq, B and β have been evaluated for most of these complexes.     

Transition metal complexes with 1,3-bis-(2-hydroxyphenyl)-1,3-propanedione—I : Mononuclear complexes

Reaction of 1,3-(2-hydroxyphenyl)-1,3-propanedione (BhPPH₃), a ligand with three possible sites of coordination acting as a chelating agent, with metal acetates results in the formation of mononuclear species M(BhPPH₂)₂S,S′ (M=Mn, Fe, Co, Ni, Zn; S,S′=CH₃OH, C₂H₅OH or H₂O); M′(BhPPH₂)₂ (M′=Cu, Pd), and M″(BhPPH₂)₃S,S′ (M″= Fe, Al). The complexes have been studied by ¹H-NMR when possible, and IR spectra. The position of the methine proton (=CH-) at 6.88 ppm in Zn(BhPPH₂)₂S,S′ indicates that BhPPH₃ behaves in mononuclear complexes as a common β-diketone. Most of the complexes lose S,S′ molecules on heating but a crystal structure of Zn(BhPPH₂)₂ · 2C₂H₅)OH indicates that the C₂H₅OH molecules are oxygen bonded to the metal centre.     

Synthesis and characterization of two Ni(II) complexes with furfural s-methylthiosemicarbazone

Synthesis of two Ni(II) complexes with furfural S-methylthiosemicarbazone (HL) of the formula [Ni(HL)₂(H₂O)₂](ClO₄)₂ (A) and [Ni(HL)₂(ClO₄)₂] (B) are reported. Compound A was obtained from an ethanolic solution of Ni(ClO₄)₂·6H₂O and HL, whilst compound B was produced by heating compound A to 378 K. An X-ray analysis of the complex A showed that it has a trans(H₂O)-trans(HL) octahedral configuration in which HL behaves as a bidentate (NN) ligand. On the basis of the IR and electronic spectra as well as the magnetism, it was found that the compound B has also an octahedral configuration in which, HL and ClO₄ groups, are coordinated.     

Binuclear 2,2′-bipyrimidine complexes derived from chromium,molybdenum and tungsten carbonyls

Reaction of 2,2′-bipyrimidine (bpym) with [Mo(CO)₄(diene)] gives [Mo(CO)₄(bpym)], which will react with [M(CO)₄(diene)] to form [MoM(CO)₈(bpym)] (M = Cr, Mo, W). The bipyrimidine complexes are characterised by microanalysis and spectroscopy (IR, ¹H and ¹³C NMR, UV/vis). Reduction of [Mo₂(CO)₈(bpym)] produces an anion in which the unpaired electron is localised on the bridging bpym ligand.     

Copper(II) complexes of thiosemicarbazones derived from 2-acetylpyridine and its n-oxide

A series of Cu(II) complexes of the thiosemicarbazone, 3-azabicyclo[3.2.2]-nonene-3-thiocarboxylic acid 2-[1-(2-pyridinyl)ethylidene]hydrazide(HL) and the corresponding N-oxide (HLO) have been prepared and characterized. Both ligands undergo deprotonation and appear to coordinate via the thione sulfur, the imine nitrogen and the pyridyl nitrogen (or N-oxide oxygen). A single anionic ligand such as Cl^?, Br^?, NCS^? and N^?₃ completes the bonding to the Cu(II) center of these 4-coordinate complexes. When the complexes are prepared using Cu(II) perchlorate, the solids isolated contain a neutral thiosemicarbazone ligand as well as the deprotonated ligand. The solids are primarily characterized by IR, electronic and electron spin resonance spectroscopy. In addition, electronic and ESR spectra of their chloroform solutions were recorded. Most of the solids (except the nitrates) were unaltered upon dissolution. Simulation of the solution ESR spectra was used to estimate the coupling constants of the various coordinated nuclei.     

Preparation and characterization of heterobimetallic tetraxanthates and their complexes with Lewis bases

Some new heterobimetallic tetraxanthates of the type M[Ag(Etxant)₂]₂ [M = Co(II) or Ni(II), Etxant = ethylxanthate] and their complexes of general formula M[Ag(Etxant)₂]₂.xL [x = 2 when L= dimethylsulphoxide (DMSO), triphenylphosphine (Pph₃), pyridine(py) or 2-aminopyridine (2-ampy); x = 3 when L = 2,2′-bipyridine (bipy)] have been prepared and characterized by elemental analysis, molar conductance, magnetic susceptibility, infrared and electronic spectral studies. Magnetic and electronic spectral studies indicate square planar geometry around Ni(II) and Co(II) in heterobimetallic tetraxanthates and Ni[Ag(Etxant)₂]₂.2PPh₃ and octahedral geometry around the above metal ions in the remaining complexes.     

Organotellurium cations: Organotellurium perchlorates and their complexes with Lewis bases

Solutions of diorganotellurium(IV) diperchlorates R₂Te(ClO₄)₂ (where R = Ph, p-CH₃OC₆H₄, R₂Te = $\text{C}{}_4\text{H}{}_8\text{Te}$) may be prepared by the reaction of R₂TeCl₂ and AgClO₄ or by the reaction of diorganyltelluroxide with excess of 70% HClO₄.IR and conductivity data indicate that Ph₂Te(ClO₄)₂ possesses covalently bonded perchlorate groups in solution. Interaction of the freshly prepared solutions with Lewis bases affords cationic complexes of the types [R₂Te(ClO₄)(L)][ClO₄] and [R₂Te(L)₂][ClO₄]₂ which have been characterised by IR elemental analyses and conductivity measurements.     

Fluoride complexes of the alkali metal ions

Measurements by fluoride ion-selective electrode potentiometry on the very weak monofluoride complexes of the alkali metal ions in aqueous solution at 25°C and an ionic strength of 1M indicate their stability constants lie in the order Li⁺ > Na⁺ > K⁺ > Rb⁺ ? Cs⁺. Data at varying ionic strengths and temperatures were used to calculate infinite dilution stability constants and enthalpies and entropies of complexation for LiF and NaF.     

Synthesis,X-ray structure and spectroscopy of Cu(II) complexes derived from diacetylazine dioxime

Complexes of Cu(II) with the polydentate diacetylazine dioxime ligand C₈H₁₄N₄O₂ have been synthesized by template and non-template reactions. The crystal structure of [Cu(C₈H₁₃N₄O₂)]₂[ClO₄]₂(C₂H₅OH)₂ has been determined to establish the conformation of the ligand and the coordination of the oxime function. The structural analysis shows that the nearly planar [C₈H₁₃N₄O₂]^? group behaves as a bridging tetradentate ligand. The distorted square-pyramidal coordination about each Cu atom includes three N donors from two oxime and azine and one O donor from the other oxime, the ethanol molecule occupying the apical position. A perchlorate anion is loosely bonded to Cu. The intramolecular Cu…Cu separation is 3.725(2) Å. The compound crystallizes in the centrosymmetric space group P$\text{1}$ triclinic lattice with refined lattice parameters of a = 11.963(8) Å, b = 9.784(7) Å, c = 7.501(6) Å, α = 90.69(4)°, β = 104.53(4)°, γ = 90.83(4)°, V = 849.7 ų and Z = 2. Full-matrix least-squares refinement of 1490 independent reflexions led to final discrepancy indices, R = 0.059, and R_w = 0.065. The Cu centres are highly coupled as indicated by the ESR spectrum. There is no evidence that the C₈H₁₄N₄O₂ ligand stabilizes unusual oxidation states of Cu.     

A new example of ligand-to-metal electron-transfer process : one-electron reduction products of nickel(II)-tetradentate schiff base complexes

The reduction of three nickel(III) complexes involving two symmetrical N,N′-ethylenebis (acetylacetoneiminato) and N,N′-ethylenebis (salicylideneiminato) and one non-symmetrical N,N′-ethylene (acetylacetoneiminatosalicylideneiminato) and Schiff bases has been investigated by electrochemistry and ESR spectroscopy. In all cases, exhaustive reduction results in the formation of nickel(I) complexes. However, ESR data support the formation of a nickel(II)-stabilized ligand radical species at the early stage of the reduction of the non-symmetrical Schiff base complex.     

NMR study of intramolecular processes in EDTA metal complexes

The kinetics of the intramolecular acetate scramblings occurring in thirteen ethylenediaminetetraacetate (EDTA) complexes has been studied by analyzing the modification observed in the NMR spectra of their D₂O solutions, when temperature is changed. The experimental results indicate that the Δ, Λ conversion is a fast process on the NMR time scale for each of the complexes considered, whereas the nitrogen inversion occurs at an observable rate in the case of the Cd(II), In(III), Sc(III), Y(III) and Lu(III) chelates and is too rapid in the other complexes. Computer analysis of the experimental NMR spectra has been performed in order to obtain enthalpy, entropy and free energy of activation concerning the N inversion of the cited chelates. Twist and bond breaking mechanisms are discussed with reference to both scrambling processes.     

Alkali metal complexes: Complexes of alkali metals with quinaldinic acid

Complexes having the general formula ML.HL, where M = Na, K, Rb or Cs and HL = quinaldinic acid, have been obtained. The isolation of adducts in the solid state appeared to be favoured by increase in atomic radius, and hence decrease in ionisation potential of the metal. Attempts to synthesise similar adducts of picolinic acid N-oxide and quinaldinic acid N-oxide did not succeed. Complexes have been characterised by elemental analyses, thermal, IR spectral and solution studies. Our findings suggest that pK value of the ligands cannot be regarded a dominant factor in the synthesis and isolation of alkali metal complexes.     

X-ray photoelectron spectra of metal complexes of substituted 2,4-pentanediones

The X-ray photoelectron spectra of 14 complexes of Al³⁺, Cr ³⁺, Fe³⁺, Co³⁺ and Cu²⁺ with 3-X-2,4-pentanedione (X = H, Cl, Br) were determined to analyse the nature of metal-ligand bonding in these complexes. The trend in the position of np photoelectron lines of X-group with a change of metal ion was decided by the relative contribution of metal-toligand and ligand-to-metal charge transfer. The analysis of the satellites in the M(2p_3/2) and M(2p_1/2) spectra suggested that the metal-ligand bond in the chromium(III) complex had higher covalent character than that in the iron(III) complex. The satellite separations in the O(1s) spectra of M(3-Xptdn)₃ were in the range 4.0-4.8 eV: these satellites were assigned to a shake-up transition of Lπ → Lπ^* character. The O(1s) spectra of Fe(3-Xptdn)₃ and A1(3-Xptdn)₃ displayed an additional strong peak to higher energy than that of the main peak (δE = 2.1–3.1 eV) when the samples of complexes were bombarded with argon ions for a longer time.     

The interaction of morpholine with metal ions—I: Copper complexes

The synthesis and electronic and IR spectra of CuL₂(NO₃)₂ and CuL₄(NO₃)₂, where L stands for morpholine, are described. The thermal behaviour of the complexes is also discussed. The solids contain distorted octahedral Cu(II) bonded to morpholine through nitrogen only. In aqueous solutions only the species CuL₃(aq)²⁺ is stable in the concentration range 0.5 < [L] < 2 mol dm^?3, its stability constant being log K₃ = 14.64 ± 0.15 at 25.00°C and ionic strength 1 mol dm^?3; at very high morpholine concentrations, 3.4 < [L] < 6 mol dm^?3, evidence is also found for CuL₄(aq)²⁺, the value log K₄ = 15.5 being estimated. The aggressiveness of morpholine-H₂O₂ towards metallic copper is compared with that of ammonia-H₂O₂, both on thermodynamics and kinetics grounds; experimental results seems to be dominated by kinetics factors. The relevance of these results to water treatment in secondary systems of nuclear power reactors is discussed.