Cobalt(II) complexes of 1,2-(diimino-4′-antipyrinyl)ethane and 4-N-(4′-antipyrylmethylidene)aminoantipyrine

Cobalt(II) complexes of the Schiff bases 1,2-(diimino-4-antipyrinyl)ethane (GA) and 4-N-(4-antipyrylmethylidene)aminoantipyrine (AA) have been prepared and characterised by elemental analysis, electrical conductance in non-aqueous solvents, i.r. and electronic spectra, as well as by magnetic susceptibility measurements. The complexes have the general formulae [Co(GA)X]X (X = ClO^– ₄ or NO₃ ^–), [Co(GA)X₂] (X = Cl^–, Br^– or I^–), [Co(AA)₂]X₂ (X = ClO₄ ^–, NO₃ ^–, Br^– or I^–) and [Co(AA)Cl₂]. GA acts as a neutral tetradentate ligand, coordinating through both carbonyl oxygens and both azomethine nitrogens. In the perchlorate and nitrate complexes of GA one anion is coordinated in a bidentate fashion, whereas in the halide complexes both anions are coordinated to the metal, generating an octahedral geometry around the Co ion. AA acts as a neutral bidentate ligand, coordinating through the carbonyl oxygen derived from the aldehydic moiety and the azomethine nitrogen. Both anions remain ionic in the perchlorate, nitrate, bromide and iodide complexes of AA, whereas both anions are coordinated to the metal ion in the chloride complex, resulting tetrahedral geometry around the Co ion.     

Metal chelates of heterocyclic nitrogen containing ketones,XIII. Cobalt(II), nickel(II) and palladium(II) complexes of 2-picolyl- and 2-lutidyl-methyl ketones

Summary The preparation and characterization of a series of new coordination compounds of cobalt(II), nickel(II) and palladium(II) containing 2-picolyl- or 2-lutidyl-methyl ketone (HPMK or HLMK) and various anions, Cl^–, Br^–, NO ₃ ^– , NCS^– or BF ₄ ^– , are reported. Complexes of square planar, tetrahedral and octahedral stereochemistry as well as five-coordinate species were isolated. The reaction products were found to be dependent on the molar ratios, pH and the temperature at which the reaction takes place. Cobalt(II) thiocyanate was found to form a complex of the type [CoL₃][Co(NCS)₄] (L = HPMK or HLMK). Also complexes containing coordinated BF₄ were isolated. The ligand field parameters (Dq, B and ) for the cobalt(II) and nickel(II) complexes were calculated using the averaged-ligand-field approximation. The influence of the substituents of theses parameters and on the stereochemistry are discussed.     

X-ray photoelectron spectra of tetraaza macrocyclic complexes of cobalt with molecular oxygen

X-ray photoelectron spectroscopy has been used to determine the electronic state of the cobalt-molecular-oxygen fragment, the type of coordination, and, in some cases, the nature of the bond between the central ion and the axial ligand in the complexes [Co^II(htd)(NCS))C10₄, [-O₂{Co(htd((X)}₂](ClO₄)₂ (X=NCS^–, N₃ ^–, NCO^–, OH^–), and [O₂{Co(htd)(Im)}₂](ClO₄)₄. It has been established that the NCO^– and NCS^– ligands are coordinated as electron donors in an axial position by means of their nitrogen atoms. A conclusion regarding the electronic structure of the Co^III-O₂ ^2–-Co^III fragment has been drawn on the basis of an analysis of the binding energy (E_b) of the Co 2p_3/2 electrons in the oxygenated complexes and in the corresponding low-spin cobalt(II) compounds and cobalt(III) compounds.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 4, pp. 437–442, July–August, 1990.     

Transition metal ion complexes of theS-methyldithiocarbazate prepared from 2-acetylpyridine

Summary Metal ion complexes of 2-acetylpyridineS-methyldithiocarbazate, HNNS, have been prepared and spectrally characterised. Preparations in EtOH yield complexes in which the deprotonated ligand, NNS, is complexedvia its pyridyl nitrogen, azomethine nitrogen, and thione sulphur. The stoichiometries are: [M(NNS)₂]X (M=Fe³⁺, Co³⁺ and X=ClO ₄ ^– , [FeCl₄]^–, BF ₄ ^– , 1/2 [CoCl₄]^2– and 1/2 [CoBr₄]^2–), [M(NNS)X] (M=Ni²⁺, Cu²⁺ and X=Cl^–, Br^–), [Cu(NNS)H₂O]BF₄ and Ni(HNNS)(NNS)F(EtOH)]BF₄. The spectral (i.e., i.r., u.v.-vis.-n.i.r. and e.s.r.) and physical properties of these complexes are compared to those of theS-methyldithiocarbazates of 2-formylpyridine and 2-acetylpyridineN-oxide, as well as the related thiosemicarbazones prepared from 2-acetylpyridine. Thermal studies of the nickel(II) complexes indicate that the nature of thermal decomposition of coordinated NNS is different from that of HNNS.     

Studies on the kinetics and mechanism of dissociation of copper(II) and nickel(II) complexes of the macrocyclic ligand 1, 5, 9, 13-tetraaza-2, 4, 4, 10, 12, 12-hexamethyl-cyclohexadecane-1, 9-diene in perchloric acid media

Summary Acid catalysed dissociation of the copper(II) and nickel(II) complexes (ML²⁺ of the quadridentate macrocyclic ligand 1, 5, 9, 13-tetraaza-2, 4, 4, 10, 12, 12-hexamethyl-cyclohexadecane-1, 9-diene (L) has been studied spectrophotometrically. Both complexes dissociate quite slowly with the observed pseudo-first order rate constants (k_obs) showing acid dependence; for the nickel(II) complex (k_obs)=k_O+k_H[H⁺], the k_o path is however absent with the copper(II) complex. At 60°C (I=0.1M) the k_H values areca 10^–4 M^–1 s^–1 for both complexes; k _H ^Cu /k _H ^Ni =ca. 3.9, comparable to some other square-planar complexes of these metal ions. The rate difference is primarily due to H values [copper(II) complex, 29.4±0.5 kJ mol^–1; nickel(II) complex, 35.6±1.5 kJ mol^–1] with highly negative S values [for copper(II), –215.5 ±6.1 JK^–1 mol^–1 and for nickel(II), –208.1 ±5.6 JK^–1 mol^–1] which are much higher than the entropy of solvation of Ni²⁺ (ca. –160 JK^–1 mol^–1) and Cu²⁺ (ca. –99 JK^–1 mol^–1) ions; significant solvation of the released metal ions and the ligand is indicated.     

Studies of artificial hydrolytic metalloenzymes: The catalyzed carboxyester hydrolysis by copper(II), zinc(II) and cobalt(II) complexes of the tripod ligand tris(2-benzimidazylmethyl)amine

The hydrolysis kinetics of p-nitrophenyl acetate (NA) catalyzed by Cu^II, Zn^II and Co^II complexes of tris(2-benzimidazylmethyl)amine (NBT) have been studied. The hydrolysis rate is first-order in both metal(II) complex and NA. The second-order rate constants, k_cat are 0.083, 0.241 and 0.285mol^–1Ls^–1 (298K, I = 0.10molL^–1 KNO₃, 0.02molL^–1 tris buffer, 40% MeCN aqueous solution) for Zn–NBT, Co–NBT and Cu–NBT complexes, respectively. The result indicates that the hydrolytic metalloenzyme activity of different metal complexes increases with the electrophilicity of the metal ions and that the complexes, in this paper, constitute that most efficient hydrolytic metalloenzyme models reported to date. An increase in MeCN content in the solution greatly reduces the hydrolytic activity of the nucleophiles.     

Outer-sphere electron-transfer reactions with the participation of platinum(IV) haloammines

The kinetics of some outer-sphere electron-transfer reactions with the participation of the complexes [Pt(NH₃)_nX_6–n]² (n=6–0, X=Cl^–, Br^–) and dipyridyl complexes of Os(II), Ru(II), Ir(III), and Cr(II) have been investigated by means of luminescence-quenching measurements and flash photolysis. Estimates of the values of the Pt(IV)/Pt(III) one-electron potential and the change in the free energy of activation of electron self-exchange processes of the type Pt(IV) Pt(III) have been obtained on the basis of an analysis of the dependence of the rate constant on the change in the free energy accompanying the electrontransfer process.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 26, No. 4, pp. 455–462, July–August, 1990.     

A selective and sensitive spot-test for gold

Summary A new spot test for gold has been developed, based on the oxidation of colourless phenolphthalin to red phenolphthalein in alkaline medium. The sensitivity is 0.2g of gold on a spot-plate and 0.15g on filter paper. Ce(IV) interferes seriously, and Pt(IV) at high concentrations, but Pd(II), Cu(II), Fe(III), Cr(III), Ni(II), UO₂(II), ClO₄ ^–, CrO₄ ^2–, BrO₃ ^–, IO₃ ^–, MoO₄ ^2–, and WO₄ ^2– do not.

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Zusammenfassung Eine neue Tüpfelreaktion für Gold wurde entwickelt, die auf der Oxydation des farblosen Phenolphthalins zu rotem Phenolphthalein in alkalischem Milieu beruht. Die Empfindlichkeit beträgt auf der Tüpfelplatte 0,2g Gold, auf Filterpapier 0,15g. Cer(IV) stört stark, Pt(IV) in hoher Konzentration; hingegen stören Pd(II), Cu(II), Fe(III), Cr(III), Ni(II), UO₂(II), ClO₄ ^–, CrO₄ ^2–, BrO₃ ^–, JO₃ ^–, MoO₄ ^2– und WO₄ ^2– nicht.

     

Synthetic and kinetic studies on copper(II), nickel(II) and cobalt(III) complexes of 1,4,7,10,13-pentaazacyclohexadecane ([16]aneN5)

Summary The pentadentate macrocycle 1,4,7,10,13-penta-azacyclo-hexadecane [16]aneN₅=(3)=L} has been prepared and a variety of copper(II), nickel(II) and cobalt(III) complexes of the ligand characterised. The copper complex [CuL](ClO₄)₂, on the basis of its d-d spectrum, appears to be square pyramidal, while [NiL(H₂O)](ClO₄)₂ is octahedral. The copper(II) and nickel(II) complexes dissociate readily in acidic solution and these reactions have been studied kinetically. For the copper(II) complex, rate=k_H[complex][H⁺]² with k_H =4.8 dm⁶ mol^–2s^–1 at 25 °C and I=1.0 mol dm^–3 (NaClO₄) with H=43 kJ mol^–1 and S ₂₉₈ =–89 JK^–1 mol^–1. Dissociation rates of the copper(II) complexes increase with ring size in the order: [15]aneN₅ < [16]aneN₅ < [17]aneN₅. For the dissociation of the nickel(II) complex, rate=k_H[Complex][H⁺] with k_H=9.4×10^–3 dm³mol^–1 s^–1 at 25 °C and I =1.0 mol dm^–3 (NaClO₄) with H=71 kJ mol^–1 and S ₂₉₈ =–47 JK^–1mol^–1.The cobalt(III) complexes, [CoLCl](ClO₄)₂, [CoL(H₂O)]-(ClO₄)₃, [CoL(NO₂)](ClO₄)₂, [CoL(DMF)](ClO₄)₃ (DMF=dimethylformamide) and [CoL(O₂CH)](ClO₄)₂ have been characterised. The chloropentamine [CoCl([16]aneN₅)]²⁺ undergoes rapid base hydrolysis with k_OH=1.1× 10⁵dm³ mol^–1s^–1 at 25°C and I=0.1 mol dm^–3 (H=73 kJ mol^–1 and S ₂₉₈ =98 JK^–1 mol^–1). Rapid base hydrolysis of [CoL(NO₂)]²⁺ is also observed and the origins of these effects are considered in detail.     

Complexes of N-nicotinoyl-N′-2-furanthiocarbohydrazide with oxovanadium(IV), manganese(II), iron(II & III), cobalt(II), nickel(II), copper(II) and zinc(II)

A new potential tetradentate ligand, N-nicotinoyl-N-2-furanthiocarbohydrazide (H₂Nfth), and its complexes with VO^IV, Mn^II, Fe^II,III, Co^II, Ni^II, Cu^II and Zn^II have been prepared and characterized by elemental analyses, magnetic susceptibility measurements, u.v.–vis, i.r., n.m.r., ES⁺ and FAB mass spectral data. The room temperature e.s.r spectra of the VO^IV and Fe^III complexes yield g values, characteristic of octahedral complexes. The Mössbauer spectra of [Fe(HNfth)₂] and [Fe₂(Nfth)₃] at room temperature and at 78 K suggest the presence of high-spin iron(II) and iron(III), respectively. The complexes are electrically insulating at room temperature, however, their conductivities increase as the temperature increases from 333–383 K, with a band gap of 0.46–0.77 eV, indicating their semiconducting behaviour. H₂Nfth and its soluble complexes have been screened against several bacteria and fungi.     

Determination of the calibration constant of the isomer shift of 57Fe Mössbauer spectra

Results are presented from quantum-chemical calculations for the iron complexes Fe(CN)₅NO^2–, Fe(CN)₆ ^3–,Fe(CN)₆ ^4–, FeCl₄ ^–, and FeCl₆ ^3– in comparison with Mössbauer-spectroscopic data. The parameters of the Mössbauer spectra were calculated according to specially developed programs. The calibration constant of the isomer shift was determined to be –0.13 mm/sec.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 23, No. 4, pp. 506–508, July–August 1987.     

Complexes of dioxouranium(VI) with zwitter-ionic forms of Bi- and tetra-dentateSchiff bases

Potentially bi- and tetra-dentateSchiff bases derived from salicylaldehyde react with hydrated uranyl salts to give complexes: UO₂H₂ LX ₂, UO₂H₂ LX ₂ and UO₂(HL)₂ X ₂ [H₂ L=N,N-propane-1,3-diylbis(salicylideneimine), H₂ L=N,N-ethylenebis(salicylideneimine) and HL=N-phenylsalicylideneimine;X ^–=Cl^–, Br^–, I^–, NO₃ ^–, ClO₄ ^–, and NCS^–]. Because of marked spectral similrities with the structurally known Ca(H₂ L) (NO₃)₂, theSchiff bases are coordinated through the negatively charged phenolic oxygen atoms and not the nitrogen atoms of the azomethine groups which carry the protons transferred from phenolic groups on coordination. Halide, nitrate, perchlorate and thiocyanate groups are covalently bonded to the uranyl ion, resulting a 6-coordinated uranium ion in the halo and thiocyanato complexes and 8-coordinated in nitrato and perchlorato complexes.

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Komplexe von Dioxouranyl(VI) mit zwitterionischen Formen von zwei- und vierzähnigen Schiff-Basen

Zusammenfassung Von Salizylaldehyd abgeleitete zwei- und vierzähnigeSchiff-Basen reagieren mit hydratisierten Uranylsalzen zu Komplexen folgenden Typs: UO₂H₂ LX ₂, UO₂H₂ LX ₂ und UO₂(HL)₂ X ₂ [H₂ L=N,N-Propan-1,3-diylbis(salicylidenimin), H₂ L=N,N-Ethylen-bis(salicylidenimin) und HL=N-Phenylsalicylidenimin;X ^–=Cl^–, Br^–, I^–, NO₃ ^–, ClO₄ ^– und NCS^–]. Auf Grund eindeutiger spektraler Ähnlichkeiten mit dem bekannten Ca(H₂ L) (NO₃)₂ wird auf Koordination über die negativ geladenen phenolischen Sauerstoffatome (und nicht über die Azomethin-Stickstoffe) geschlossen. Die AnionenX ^– sind kovalent an das Uranyl-Ion gebunden; damit ergibt sich ein hexakoordiniertes Uranyl-Ion für die Halogen- und Thiocyanat-Komplexe und Oktakoordination für die Nitrat- und Perchlorat-Komplexe.

     

Copper(I) complexes of neutral,deprotonated and protonated 4,6-dimethylpyrimidine-2 (1H)-thione

Summary The following copper(I) complexes of 4,6-dimethylpyrimidine-2(1H)-thione (HL), its protonated cation (H₂L⁺) and deprotonated anion (L^–) have been prepared: CuL, Cu(HL)X (X = Cl, Br or I), Cu(HL)₂X (X = C1 or Br), Cu₂(HL)₃Br₂, Cu(H₂L)X₂ (X = Cl or Br), Cu₃(HL)₂LA₂ (A = ClO₄ or BF₄ ). The i.r. spectra show that in all the HL and L^– complexes and in the Cu(H₂L)Br₂ complex, the ligands are S, N coordinated to the metal ion, while in Cu(H₂L)Cl₂ only the thiocarbonylic sulphur is coordinated, probably bridging two copper(I) atoms. Thev(CuN) (288–317 cm^–1 ) andv(CuS) (191–225 cm^–1 ) have uniform frequency values in all the complexes. The halide ions are, in all their complexes, wholly or in part coordinated giving twov(CuX) bands which may indicate an asymmetrical Cu-X Cu halide bridging bond.Author to whom all correspondence should be directed.     

Synthesis of 4-Dicyclohexylaminomethyl Antipyrine and Its Metal Complexes: Spectral Characterization and Evaluation of Thermodynamic Parameters

Complexes of Fe(III), Co(II), Ni(II), and Cu(II) with 4-dicyclohexylaminomethyl antipyrine (DCHAMA, L) were prepared and characterized by elemental and chemical analyses, IR, electronic absorption, ¹H NMR and EPR spectroscopies, thermal analysis, and magnetic susceptibility measurements. The stoichiometry of the complexes was found to be MLX₂, MLX₃, or MLX₂(H₂O)₂ where X = Cl or NO₃. The ligand exhibits a bidentate mode of coordination. Thermal analysis of the chloro complexes shows a three stage decomposition pattern for the Cu(II) complex and a two stage decomposition pattern for Fe(III) and Co(II) complexes to yield the respective metal oxides as the end product. Kinetic and thermodynamic parameters such as n, E _a, H ^#, S ^#, and G ^# were calculated using Coats–Redfern and Madhusudhanan–Krishnan–Ninan integral methods. The coordination number of the metal atom is found to influence the thermal stability of the complexes. The antimicrobial screening shows that the four-coordinated complexes are more active than the five- and six-coordinated ones and DCHAMA.     

An investigation of mononuclear and binuclear palladium(II) complexes of egta (egta = glycine,N,N′-(1,2-ethanediylbis(oxy-2,1-ethanediyl)bis[N-carboxymethyl]) by 1H-, 13C- and 15N-n.m.r. methods

1:1 and 2:1 palladium(II) complexes of egta^4– (egta^4– = glycine, N,N-(1,2-ethanediylbis)(oxy-2,1-ethanediyl)bis[N-carboxymethyl]) were prepared by 1:1 and 2:1 addition of K₂PdCl₄ to K₄egta, and examined by ¹H-, ¹³C- and ¹⁵N-n.m.r. methods. The 1:1 complex, [Pd(egta)]^2– in solution, utilizes a square-planar coordination comprised of two nitrogen and two glycinato carboxylate donors of egta^4–, leaving two glycinato carboxylates pendant. The complex has a cis-(R,S) stereochemistry which places both pendant carboxylates below the PdN₂O₂ square plane and the tether backbone of egta^4– in the up, up sense above the same plane. The cis-(R,S) assignment was assisted by computer simulations of the ¹³C-n.m.r. spectrum for four possible isomers. Only cis-(R,S) and trans-(R,R) calculated ¹³C-spectra were compatible with the observed ¹³C-n.m.r. pattern. The HH NOESY spectrum of [Pd(egta)]^2– detects long range coupling of the backbone –OCH₂CH₂O– linkage with both coordinated and pendant glycinato CH₂ moieties. The cis-(R,S) isomer's tortional movements allow such contacts whereas a trans-(R,R) isomer does not. The 2:1 complex, [Pd₂(egta)(H₂O)₂] in solution has an extended-chain structure with each palladium(II) center coordinated in the mer-iminodiacetate-like coordination with two bound glycinato-functionalities.     

An ab initio study of the structures and enthalpies of the hydrogen-bonded complexes of the acids H2O,H2S,HCN, and HCl with the anions OH−, SH−, CN−, and Cl−

Ab initio calculations at second-order Møller-Plesset perturbation theory with the 6-31 + G(d,p) basis set have been performed to determine the equilibrium structures and energies of a series of negative-ion hydrogen-bonded complexes with H₂O, H₂S, HCN, and HCl as proton donors and OH^–, SH^–, CN^–, and Cl^– as proton acceptors. The computed stabilization enthalpies of these complexes are in agreement to within the experimental error of 1 kcal mol^–1 with the gas-phase hydrogen bond enthalpies, except for HOHOH^–, in which case the difference is 1.8 kcal mol^–1. The structures of these complexes exhibit linear hydrogen bonds and directed lone pairs of electrons except for complexes with H₂O as the proton donor, in which cases the hydrogen bonds deviate slightly from linearity. All of the complexes have equilibrium structures in which the hydrogen-bonded proton is nonsymmetrically bound, although the symmetric structures of HOHOH^– and ClHCl^– are only slightly less bound than the equilibrium structures. MP2/6-31 + G(d,p) hydrogen bond energies calculated at optimized MP2/B-31 + G(d,p) and at optimized HF/6-31G(d) geometries are similar. Using HF/6-31G(d) frequencies to evaluate zero-point and thermal vibrational energies does not introduce significant error into the computed hydrogen bond enthalpies of these complexes provided that the hydrogen-bonded proton is definitely nonsymmetrically bound at both Hartree-Fock and MP2.     

Preparation and properties of cationic trimethylphosphiterhodium(I) complexes with arene ligands

Summary The preparation and properties of cationic arenerhodium(I) complexes of general formula [Rh {P(OMe)₃}(⁶-arene)]A [arene=C₆H_6–nMe_n (n=0, 1, 2, 3, 4 or 6); A=ClO ₆ ^– , PF ₆ ^– ] are described. The coordinated arene is dissociated in (CD₃)₂ CO or DCCl₃ solution and this dissociation decreases with increased methyl substitution of the arene ligand.The ability of these cationic complexes to function as an intermediate for the synthesis of other rhodium(I) complexes by displacement of the coordinated arene with or -donor ligands has been studied.     

Magnetic,spectroscopic and biological properties of copper(II) complexes of the tridentate ligand, α-N-methyl-S-methyl-β-N-(2-pyridyl)methylenedithiocarbazate(NNS) and the X-ray crystal structure of the [Cu(NNS)I2] complex

Copper(II) complexes of general formula, Cu(NNS)X ₂ · nH₂O (NNS = the 2-formylpyridine Schiff base of N-methyl-S-methyldithiocarbazate; X = Cl^–, Br^–, I^–, NCS^–; n = 0, 2) have been synthesized and characterized by elemental analysis and by magnetic and spectroscopic techniques. Based on magnetic and spectroscopic data, a monomeric five-coordinate square-pyramidal structure is assigned to these complexes. The crystal and molecular structure of [Cu(NNS)I₂] has been determined by X-ray diffraction. The complex has a monomeric square-pyramidal structure with the ligand coordinated to the copper(II) ion via the pyridine nitrogen atom, the azomethine nitrogen atom and the thione sulfur atom. The fourth and fifth coordination sites are occupied by the iodide ligands. Antimicrobial tests indicate that Schiff base is inactive against the bacteria, Bacillus subtilis (mutant defective DNA repair), Pseudomonas aeruginosa, methicillin resistant Staphylococcus aureus and Bacillus subtilis (wild type) and weakly active against the fungi, Candida albicans, Candida lypolytica, Saccharomyces cereviseae and Aspergillus ochraceous but its copper(II) complexes, Cu(NNS)X ₂ are strongly active against these organisms. A cytotoxicity study of the compounds against leukemic and cervical cancer cells showed that the Schiff base is inactive, but the complexes, [Cu(NNS)I₂] and [Cu(NNS)(NCS)₂] · 2H₂O exhibit significant activity against cervical cancer cells with CD₅₀ values of 4.8 and 4.2 g, respectively.     

Polymer complexes,XXIII: Synthesis and physico-chemical studies on transition metal complexes of symmetric novel poly(N,N′-o-phenylenediamine)-bis(cinnamaldehyde)

Summary New complexes derived from polymeric N,N-o-phenylenediamine bis(cinnamaldehyde) (L) with Cu^II, Co^II, Ni^II, Zn^II, UO ₂ ^II , and Pd^II were prepared and characterized by elemental analysis, magnetic susceptibilities and spectroscopic (IR, far-IR,¹H-NMR,¹³C-NMR and EPR) studies. A bidentate methine nitrogen atoms coordination of the ligand is assigned in the isolated complexes. The stereochemistries of the polymer complexes have been studied with using magnetic and spectroscopic measurements. Analytical data show 2:1 or 1:1 (ligand:metal) stoichiometry with water molecules coordinated to the Zn^II ion, as evidenced from IR and thermal analysis (DTA). The ligand was tested as a corrosion inhibitor for copper; the limiting concentration of the ligand to give maximum efficiency (60%) is 10^–3 mol dm^–3 at 25°C.

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Polymere Komplexe, XXIII: Synthese und physikalisch-chemische Untersuchungen an Übergangsmetallkomplexen von symmetrischem Poly(N,N-o-phenylendiamin)bis(zimtaldehyd)

Zusammenfassung Es wurden neue Komplexe von polymerem Poly(N,N-o-phenylendiamin)bis-(zimtaldehyd) mit Cu(II), Co(II), Ni(II), Zn(II), UO₂(II) und Pd(II) hergestellt und mittels Elementaranalyse, magnetischen Suszeptibilitätsmessungen und spektroskopischen Methoden (IR, far-IR,¹H-NMR,¹³C-NMR und EPR) charakterisiert. Es wurde eine zweizähnige Methin-Stickstoff-Koordination in den Komplexen festgestellt. Die Stereochemie der Polymerkomplexe wurde mittels magnetischer und spektroskopischer Messungen untersucht. Aus den analytischen Daten, mit zusätzlichen Argumenten aus IR und thermischer Analyse (DTA), ergab sich eine 2:1 oder 1:1 (Ligand:Metall)-Stöchiometrie mit an Zn(II) koordinierten Wassermolekülen. Der Ligand wurde als Korrosionsinhibitor für Kupfer getestet: die Grenzkonzentration des Liganden zur maximalen Effizienz (60%) ist 10^–3 mol dm^–1 bei 25°C.

     

Bis-(tetraethylammonium)[tetraazidocuprate(II)] and catena-di-μ-1,1-azido-[di-μ-1,1-azido-bis-(2,4-dimethylpyridine)dicopper(II)]

Two new copper(II) azido complexes, namely bis-(tetraethylammonium)[tetraazidocuprate(II)] (1) and catena-di--1,1-azido-[di--1,1-azido-bis-(2,4-dimethylpyridine)dicopper(II)] (2), have been prepared and characterized by spectroscopic and crystallographic methods. Complex (1) consists of isolated NEt⁺ ₄ cations and [Cu(N₃)₄]^2– anions. The site symmetry around the copper atom in the anion is 4/m. Complex (2) features a 1 D chain structure, five coordinated square pyramidal copper(II) atoms with both azides functioning as -1,1-bridges. The i.r. spectra reveal that both complexes contain asymmetric azido ligands. The solid and solution electronic spectra of (1) and (2) show very strong absorption bands in the visible region associated with N^– ₃ Cu^II charge-transfer transitions. The e.p.r. spectra of powder samples and solutions at room temperature were recorded and discussed.