Untersuchungen an Metallchelaten mit Liganden des Cuproin- und Ferrointyps. XVII1. Struktur und Bindung von Perchlorato-bis(cuproin)- und Perchlorato-bis(ferroin)-kupfer(II)-Perchloraten

Structure and Bonding of Perchlorato-bis(cuproine)- and Perchlorato-bis(ferroine)-copper(II) Perchlorates The results of ESR, IR, and visible spectra of copper(II) chelates of the type [CuL₂ClO₄]ClO₄ (L = bipy, phen, dmp, dmch, and bich) are reported. In all cases evidences for coordinated perchlorate ions were found. On the basis of the ESR and visible spectra the bonding properties of the chelates are discussed.     

Untersuchungen an Metallchelaten mit Liganden des Cuproin- und Ferrointyps. VII. Struktur und Bindung von Diacetato-(cuproin)- und Diacetato-(ferroin)-kupfer(II)-Chelaten

Structure and Bonding of Diacetato-(cuproine) and Diacetato(ferroine) Copper(II) Chelates Copper(II) chelates of the general formula Cu(N? N)(CH₃COO)₂, where (N? N) = bipy, phen, dmch, bich, and dmp, were investigated by means of the IR, VIS, and ESR techniques. The ferroine type chelates Cuphen(CH₃COO)₂ and Cubipy(CH₃COO)₂ were found to have planar structures. For the cuproine type chelates the results are consistent with distorted tetrahedral structures. The MO parameters were estimated and discussed.     

ESR-Untersuchungen zu Struktur- und Bindungsverhältnissen von tri- und bicyclischen Cobalt(II)- und Kupfer(II)-Chelaten mehrzähniger Schiffscher Basen des Typs M(O N N O) und M(S N)2 sowie zur Sauerstoffadduktbildung der Cobalt(II) Chelate

Structural and Bonding Properties of Quadridentate and Bidentate Cobalt(II) and Copper(II) Schiff Base Complexes and Oxygenation Behavior of the Co^II Complexes. An ESR Study ESR investigations on the low-spin cobalt(II) chelates bis(benzoylacetaldehyde)-ethylendiimine-cobalt(II), bis(benzoylacetaldehyde)-1,2-cyclohexandiimine-cobalt(II) and bis(p-chlor-β-mercaptozimtaldanilato)-cobalt(II) as well as the corresponding copper(II) chelates are reported. The large anisotropy of the g tensor of the Co^II chelates caused by strong spin-orbit interactions, and the position of the maximum g tensor component g_x in the molecules obtained by comparison with the ESR spectra of the Cu^II complexes predicts a MO for the unpaired electron which consists mainly of the Co d_yz obital. In solution (CHCl₃/pyridine) the Co^II chelates react immediately with molecular oxygen forming [CoL_n(O₂)(py)] species characterized by ESR spectra with strongly reduced g tensor anisotropy and small ⁵⁹Co hyperfine coupling constants. The unpaired electron appears to be mainly localized in the O₂-part of hte molecules. The CoN₂S₂ coordination sphere shows a lower affinity to oxygen than the CoN₂O₂ type complexes. In the CuN₂O₂ complexes the unpaired electron is found to be in a MO containing the Cu d_xy orbital. Due to remarkable covalency¹⁴ N and H hyperfine interactions are observed in the ESR spectra. Analyzing the hyperfine coupling constants the extent of unpaired spin density on the N donor atoms and the N-2s/2p hybridization degree is estimated.     

Über die Koordinationstendenz saurer Aminogruppen. XVIII. Struktur- und Bindungsverhältnisse von Bis-(3-phenyl-5-pyridyl(2)-pyrazolato)-kupfer(II) - eine ESR-Studie

Bis-(3-phenyl-5-pyridyl(2)-pyrazolato)-copper(II), [Cu(PPP)₂], a brown paramagnetic nonionic chelate, is studied by ESR techniques in solution and as powder (diamagnetically diluted). The ESR spectra can be interpreted by means of a spin-Hamiltonian of axial symmetry. The bonding parameters of Cu–N bonds were calculated by interpretation of the g, Cu hfs and ¹⁴N-ligand hfs tensors. From these parameters follows that the degree of covalency of the s?- and π-bonds increases in comparision to other cationic copper(II) chelates (e.g. ethylenediamine complexes). These results are in good agreement with the chemical behaviour of [Cu(PPP)₂].     

Untersuchungen an Metallchelaten mit Liganden des Cuproin- und Ferrointyps VI Untersuchungen zur Struktur und Bindung in Sulfato-(cuproin)- und Sulfato-(ferroin)- kupfer(II)-Chelaten

Studies on Metal Chelates with Cuproine and Ferroine Type Ligands. VI. Investigations on Structure and Bonding in Sulphato(cuproine) and Sulphato-(ferroine)copper(II) Chelates Copper(II) chelates of the general formula Cu(N–N)SO₄, where (N–N) = bipy, phen, bich, dmch, and dmp², were examined by means of the IR-, VIS-, and ESR-techniques. The structures derived from these results are given. For CubipySO₄ · 2 H₂O and CuphenSO₄ · 2 H₂O the MO-parameters were calculated. Strong covalent out-of-plane-π-bondings indicating π-acceptor properties of the ligands were found to be present.     

Gemischtligandkomplexbildung durch Thermische Reaktion von Metall(II) - Thioselenocarbamaten EPR- und massenspektrometrische Untersuchungen

Mixed Ligand Complex Formation by Thermal Reactions of Metal(II) Thioselenocarbamate Chelates. EPR and Mass Spectrometric Investigations At higher temperatures metal(II) thioselenocarbamates M(R₂tsc)₂ (M = Cu, Ni, Pd, Pt) react to form M(R₂tsc)(R₂dsc) and M(R₂tsc)(R₂dtc) (dtc = dithiocarbamate, dsc = diselenocarbamate) mixed-ligand chelates. If Cu^II species are participated the mixed-ligand complex formation can be the followed by EPR spectroscopy. The reaction is irreversible, and the rate depends on the temperature, the substituent R, and the solvent used. The complexes M(Et₂tsc)(Et₂dsc) and M(Et₂tsc)(Et₂dtc) formed during the thermal reaction of M(Et₂tsc)₂ chelates (M = Ni, Pd, Pt) can be detected by EPR spectroscopy using the ligand-exchange reaction with [Cu(mnt)₂]^2?(mnt = maleonitriledithiolate). As results the spectra of [Cu(mnt)(Et₂tsc)]^?, [Cu(mnt)(Et₂dsc)]^? and [Cu(mnt)(Et₂dtc)]^? are observed.     

Voltammetrische und spektroskopische Untersuchungen zur Komplexbildung von Vanadium(IV) und Vanadium(V) mit Carbonat

Voltammetric and Spectroscopic Investigation of Complexation of Vanadium(IV) and Vanadium(V) by Carbonate Solutions which contain in addition to vanadium(IV) or vanadium(V), respectively, a high excess of bicarbonate or carbonate were studied by voltammetric and spectroscopic methods. A reversible electrode reaction occurs in the pH range 7–8 in 1 M KHCO₃. While generating V^IV from V^V electrochemically a carbonate ligand is added to V^IV. Based on ESR parameter recorded at room temperature and 77 K the existence of a V^IV carbonato complex is suggested. A comparison of these ESR parameter with those of analogous V^IV complexes leads to conclusions in view of the structure of the V^IV carbonato complex. These structural suggestions are supported by the fact that V^IV and V^V form a mixed valent dimer in HCO₃^?/CO₂-buffer of pH 7.5. Such dimers can be formed only when one of the oxygens of the V^VO₂⁺ cis-dioxo unit is able to coordinate at a basal site in the V^IV-complex. Thus, conclusions regarding the arrangement of the carbonato ligands in the monomeric V^V complex are possible too. A comparison of the complexes which are formed by V^IV and V^V with carbonate and the adducts arising from the interaction of V^IV and V^V with transferrin reveals the similarities of the both redox couples.     

Untersuchungen über (1:1)-Chelate des Curcumins mit Borsäure und Phenylborsäuren

The existence of 1∶1 boron-curcumin chelates in solution has been proved by the straight-line method of Asmus. The compounds with boric resp. phenylboronic acid propably exist as diacetato-resp. phenylacetato-boron chelates of curcumin. The dissociation constants of the 1∶1 complexes of curcumin and boron are K _D =4×10^?5 with boric acid in acetic acid and 3×10^?4 in dioxan, 1×10^?3 with phenylboronic acid in dioxan and 1×10^?4 when stabilized with phenol, 7×10^?5 with diphenylborinic acid in dioxan solution. All boron-curcumin chelates are formed from the quinonoid protonized form of curcumin, which can be stabilized by phenol.     

Wechselwirkungen von Hetero-π-Systemen mit Zentralmetallatomen in niedrigen Oxydationsstufen. ESR-Untersuchungen zur Struktur und Bindung an Niedrig-spin-d5-(S = 1/2)-Tris(benzil-bis-N-phenylimin)vanadium(0) und Bis(benzil-bis-N-phenylimin)cobalt(0)

Interaction of Hetero-π-Systems with Central Metal Atoms in Low Oxidation States. ESR Investigations on Structure and Bonding in Low Spin d⁵-(S = 1/2)-Tris(benzil-bis-N-phenylimine)vanadium(0) and Bis(benzil-bis-N-phenylimine)cobalt(0) ESR investigations on V(N??N)₃ and Co(N??N)₂(N??N: Benzil-bis-N-phenylimine) are reported. The ESR parameters — g, A^V — indicate trigonal coordination geometry (D₃) for V(N??N)₃ disturbed by a small lower-symmetric ligand-field component. Interpretation of these parameters in terms of a ligand-field model for a low-spin d⁵ electronic configuration shows the electronic ground state to be ²A₁ and yields a large value for the trigonal field splitting parameter K. The ESR spectrum of Co(N??N)₂ could be obtained at 4.2 K only. Its rhombic symmetry and the absence of hyperfine interactions with the nuclei ⁵⁹Co and ¹⁴N is consistent with a rhombically distorted, compressed tetrahedral symmetry (D₂) for Co(N??N)₂. The spin-Hamiltonian parameters are discussed in terms of the metal-ligand bond character and the electronic spectrum.     

Coordination compounds of hydrazine derivatives with transition metals,Part 17. Nickel (II) and cobalt(II) chelates with pyridine-2-aldehyde semi- and thiosemicarbazone

Summary The chelation abilities of both pyridine-2-aldehyde semicarbazone (Pysc) and thiosemicarbazone (Pytsc) towards Ni^II and Co^II salts have been investigated. A series of pentacoordinate monoligand chelates: Ni(Pysc)X₂, Ni(Pytsc)X₂ and Co(Pysc)X₂ and octahedral bis ligand chelates Ni(Pysc)₂X · NO₃ Ni(Pytsc)₂X₂ and Co(Pysc)₂X₂ have been isolated and identified. In these chelates, both Pysc and Pytsc act as neutral tridentate ligands. The deprotonated form of Pyts, which arises through enolization, is identified in N^II chelates and is of the type Ni(PytscH)₂ and Ni(PytscH)X. Spectral and magnetic measurements are presented and attention is drawn to the effect of temperature on the solution spectra of some of the chelates.     

Untersuchungen zur Alkylierung von Bis-Stilbendithiolato-Komplexen des Ni(II), Pd(II) und Pt(II)

Investigation on the Alkylation of Bis-Stilbendithiolato Complexes of Ni^II, Pd^II, and Pt^II Alkylation reactions of co-ordinated ligands of the type of ethylene-bisthiol R₂S₂C₂²-proceed different depending on the substituents R. The neutral complexes isolated by a alkylation of the nickel bis-chelates (R = phenyl) according to Schrauzer and Rabinowitz and formulated by these authors as mixed ligand chelates of dithiolate and diether, were identified by us as complexes of the monoethers of the ligand. These nickel (II) complexes of the mono-ethers can not be alkylated further by alkyliodides. Oxidative coupling of two ligands yields disulfides which have been identified by mass spectroscopy thus indicating the original position of attack of the alkylating reagent. The formation of bis-monether complexes is reflected by the different charges on the S atoms of the model complex [Ni(CH₃S₂C₂H₂)(S₂C₂H₂)]- obtained from EHT and CNDO calculations. Both possible stereo-isomers have been isolated of the bis-methylmonether complex of Pt(II). Trans-[M((CH₃)(S₂C₂Ph₂))₂] (M = Ni(II), Pd(II)) form CH₂Cl₂ adducts. By treating the Ni-bis complexes of the monoalkylthioethers with iodine polyiodides are prepared. Binuclear Pd(II) complexes of composition [Pd₂((R)(S₂C₂Ph₂))₂Cl₂] could be prepared by metal exchange.     

Thermal characterization of new complexes of Zn(II) and Cd(II) with some bipyridine isomers and propionates

New mixed ligand complexes of the following stoichiometric formulae: M(2-bpy)₂(RCOO)₂·nH₂O, M(4-bpy)(RCOO)₂·H₂O and M(2,4’-bpy)₂(RCOO)₂·H₂O (where M(II)=Zn, Cd; 2-bpy=2,2’-bipyridine, 4-bpy=4,4′-bipyridine, 2,4′-bpy=2,4′-bipyridine; R=C₂H₅; n=2 or 4) were prepared in pure solid-state. These complexes were characterized by chemical and elemental analysis, IR and conductivity studies. Thermal behaviour of compounds was studied by means of DTA, DTG, TG techniques under static conditions in air. The final products of pyrolysis of Cd(II) and Zn(II) compounds were metal oxides MO. A coupled TG/MS system was used to analyse of principal volatile products of thermal decomposition or fragmentation of Zn(4-bpy)(RCOO)2·H2O under dynamic air and argon atmosphere. The principal species correspond to: C⁺, CH⁺, CH₃ ⁺, C₂H₂ ⁺, HCN⁺, C₂H₅ ⁺ or CHO⁺, CH₂O⁺ or NO⁺, CO₂ ⁺, ¹³C¹⁶O₂ ⁺ and ¹²C¹⁶O¹⁸O⁺ and others; additionally CO⁺ in argon atmosphere.     

Struktur-Reaktivitäts-Beziehungen bei koordinativ ungesättigten Chelatkomplexen. IV. Zur Reaktion von Sauerstoff mit Cobalt(II)-Chelaten dreizähniger,dianionischer Schiffscher Basen

Structure Reactivity Correlations in Coordinatively Unsaturated Chelate Complexes. IV. Reaction of Dioxygen with Cobalt(II) Chelates of Tridentate Di-anionic Schiff Base Ligands The high-spin cobalt(II) chelates 3 form with pyridine isolable adducts which are also high-spin complexes. In the case 3 b a low-spin mono-adduct is indicated by ESR spectroscopy, which is changed time-dependently into a stable quadratic-pyramidal form. With 1, 10-phenanthroline 3 b forms a low-spin mono-adduct. The spectrophotometric titration of 3 d with pyridine indicates an equilibrium A + 2 Py ? APy₂ (β₂ = 0,36 M^?2) where A represents probably the tetrameric form of 3 d . In pyridine, 3 a , 3 b , and 3 d react with O₂ in an 1:1 ratio; 3 c binds O₂ in the ratio 2:1. The formation of superoxo complexes is indicated by ESR spectroscopy for the complexes 3 a , 3 b , and 3 d . 3 b reacts with O₂ in piperidine to give the free superoxide ion. In n-butylamine a species is formed which seems to be an ion pair with direct interactions between the free O₂^? ion and the coordinated amine nitrogen.     

Synthesis and characterisation of Cu(II), Ni(II), Mn(II), Zn(II) and VO(II) Schiff base complexes derived from o -phenylenediamine and acetoacetanilide

Neutral tetradentate N₂O₂ type complexes of Cu(II), Ni(II), Mn(II), Zn(II) and VO(II) have been synthesised using a Schiff base formed by the condensation of o-phenylenediamine with acetoacetanilide in alcohol medium. All the complexes were characterised on the basis of their microanalytical data, molar conductance, magnetic susceptibility, IR, UV-Vis¹H NMR and ESR spectra. IR and UV-Vis spectral data suggest that all the complexes are square-planar except the Mn(II) and VO(II) chelates, which are of octahedral and square pyramidal geometry respectively. The monomeric and neutral nature of the complexes was confirmed by their magnetic susceptibility data and low conductance values. The ESR spectra of copper and vanadyl complexes in DMSO solution at 300 K and 77 K were recorded and their salient features are reported.     

1H NMR Study of cis-trans Isomerization of Rhenium(III) Binuclear Complexes in Acetone Solutions

The behavior of rhenium(III) binuclear complexes K₂Re₂Hlg₈, Re₂(RCOO)₂Hlg₄ [Hlg = Cl and Br; R = CH₃, C₂H₅, (CH₃)₂CH, and (CH₃)₃C] in acetone solutions was studied by ¹H NMR. Reaction with neutral donor ligand (H₂O and hexamethylphosphoramide) induces transformation of trans-Re₂(RCOO)₂Hal₄ to solvated cis-Re₂(RCOO)₂Hal₄.     

Metallionen und H2O2. IV. Über Struktur und Aktivität der den H2O2-Zerfall katalysierenden Cu2+-Komplexe. II. Einfluss der Zahl der freien Koordinationsstellen

The Cu²⁺ chelates of the bidentate ligands 2,2′-bipyridine (I; [2]), N, N′-diglycyl-1,5-diaminopentane (VI), ethylenediamine (II; [2]), glycine (V) and pyrophosphate (III; [2]) are found–parallel to the spectrochemical series–to be more active in catalysis of H₂O₂ decomposition than the chelates of the terdentate ligands–antiparallel to the spectrochemical series–iminodiacetic acid (IX), glycylglycine (VIII), 2, 2′-diaminodiethylamine (VII) and 2, 2′, 2″-terpyridine (IV; [2]), the activity decreasing in the given series. If all four coordination positions of Cu²⁺ are engaged (e.g. complex with N, N′-di-(2-aminoethyl)-ethylenediamine (X)) the complex is inactive. The catalytic activity of the Cu²⁺-chelates is parallelled by the tendency to form ternary peroxo complexes.     

Strukturelle und magnetische Untersuchungen an Hexachlorowolframaten(V)

Structural and Magnetic Investigations of Hexachlorotungstates(V) CsWCl₆ crystallizes in the monoclinic space group C2/c with the lattice dimensions a = 12.097(8), b = 6.327(5), c = 15.30(1) Å, β = 128.4(1)° and 4 formula units. The compounds AWCl₆ (A = Rb, K, NH₄) are isotypic with CsWCl₆ as shown by powder patterns. Single-crystal photographs of [N(C₂H₅)₄]WCl₆ show monoclinic symmetry, space group P2₁/n with a = 11.737(8), b = 10.239(7), c = 7.191(5), β = 101.46(8)° and Z = 2. Both structures are composed of scarcely deformed WCl₆ octahedra. The trigonal compression of the octahedra results in a slightly negative deformation parameter according to the Figgis-model of the magnetic behaviour of d¹-systems. Above 80 K the μ² vs. T-curve is linear. This leads to a spin-orbit coupling constant of 1250 ± 200 cm^?1 and a covalence parameter of 0.6–0.8. Comparing the spectra of WCl₆, CsWCl₆ and Cs₂WCl₆ the beginning of the charge-transfer region was determined. The crystal field strength for CsWCl₆ was found as Δ = 16 000 cm^?1.     

Untersuchungen an Metallchelaten mit Liganden des Cuproin- und Ferrointyps. XXI. Struktur und Bindung der Dinitrato-mono(cuproin)- und Dinitrato-mono(ferroin)kupfer(II)-Chelate

Studies on Metal Chelates with Ligands of the Cuproin and Ferroin Type. XXI. Structure and Bonding of Dinitrato-mono(cuproin)- and Dinitrato-mono(ferroin)-copper(II) Chelates Chelates of the type Cu(N? N)(NO₃)₂ (N? N = bipy, phen, dmp, dmch, dpch, and bich) are characterized by means of e.s.r., u.v.-vis, i.r., and conductivity measurements. On the basis of these results the possible structures of these chelates both in solution and in the solid state are discussed. The MO coefficients, which could be obtained by e.s.r. measurements, are indicating a high covalency of the out-of-plane π-bonding, but only low covalency of the σ-bonding and the in-plane π-bonding.     

Untersuchungen an 1,2-Komplexen der Nickel(II)-halogenide mit N-substituierten Aminoäthylpyridinen-(2)

In the solid state complexes of the type MiL₂X₂ (L = N-substituted β-aminoethyl-pyridine; X = Cl, Br, J) have a cis-octahedral (X = Cl, Br) or a distorted trigonal bipyramidal structure (X = J). In solutions in acetone a partial dissociation occurs with the formation of NiLX₂, L, NiL₂X⁺, and X^?. Using a spectrophotometric method stability constants K_2S of the complexes NiL₂X₂ are determined. A correlation exists between log K_2s and the pK- values of the quarternary ammonium ions derived from the ligands L. Sterical factors cause the exeptional position of the chelates of β-methylaminoethylpyridine-(2).     

Spectral and thermal characteristics of copper(II) carboxylates with fatty acid chains and their benzothiazole adducts

The carboxylato–Cu(II) complexes of type [Cu₂(RCOO)₄] and their benzothiazole adducts [Cu₂(RCOO)₄bt₂] (bt = benzothiazole, R = CH₃(CH₂) _n?2, n = 12, 14, 16, 18) form the main objectives of this study. The studied carboxylato–Cu(II) complexes are formed from dimeric units to polymeric chains (chromofor CuO₅). The structural changes are due to coordination of ligand (benzothiazole). The polymeric chains of carboxylato–Cu(II) complexes degraded to discrete centrosymetric tetracarboxylate-bridged dimmers (chromofor CuO₄N). These prepared compounds [Cu₂(RCOO)₄] and [Cu₂(RCOO)₄L₂] were submitted to measurements relating to spectral (IR, UV–Vis) and thermal properties (TG, DTA, DSC).