Transition metal schiff base chelates as ligands for phenyltin(IV) chlorides

Summary Binuclear complexes of phenyltin(IV) chlorides with transition metal chelates of tetradentate Schiff bases derived from acetylacetone, benzoylacetone oro-hydroxyacetophenone and ethylenediamine or propylenediamine, of the general formula Ph_nSnCl₄-nML (where n = 1 or 2, M = Ni¹¹ or Cu¹¹ and L^2–= the Schiff base dianion), have been synthesised and characterized through elemental analysis, conductance and i.r. spectroscopic data. The coordination of metal chelates to tin involves two triply bonded oxygen atoms giving rise to an octahedral environment around Sn^IV. The molar conductance of the complexes in nitrobenzene shows the presence of the uncoordinated ML and phenyltin(IV) chloride moieties in solution.Author to whom all correspondence should be directed.     

Novel tribochemically active metal chelates of aromatic azo ligands

Novel Cu(II) and Pd(II) complexes with o-phenylaminoazo compounds were synthesized and studied by X-ray diffraction. Distorted tetrahedral chelate complex of Cu contains two six-membered CuN₃C₂ metal cycles. The complexes under study can be used as industrial lubricant additives.     

Transition metal complexes with thiosemicarbazide-based ligands

Solvate complexes of UO ₂ ²⁺ andN(1), N(4)-bis(salicylidene)-S-methylisothiosemicarbazone, (H₂Me-L¹), of general formula [UO₂(Me-L¹)S] (S= H₂O, MeOH, EtOH, Py, DMF and DMSO) were synthesized. The methanolic UO ₂ ²⁺ ” adducts of N(1)-benzoylisopropylidene-N(4)-salicylidene-S-alkylisothiosemicarbazone, (H₂R-L²,R=Me, Prⁿ) of general formula [UO₂(R-L²)· MeOH], were also prepared. Thermal decomposition of the complexes was investigated in air and argon. The complexes decompose to α-U₃O₈ in air, while in argon the decomposition is not completed up to 1000 K. The temperature and the mechanism of decomposition of the complexes are a function of the solvent belonging to the inner coordination sphere.     

Transition metal complexes with thiosemicarbazide-based ligands

The thermal decomposition and spectroscopic (reflectance and IR spectra) characterization of the newly synthesized square-pyramidal dioxovanadium(V) complexes of the type NH₄[VO₂(L)] (L is the dianion of the terdentate ligands salicylaldehyde thiosemicarbazone (ONS), halogen-substituted salicylaldehyde and 2-hydroxy-1-naphthaldehyde S-methylisothiosemicarbazones (ONN)) are described.

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Zusammenfassung Es wird die thermische Zersetzung und spektroskopische Charakterisierung (Reflexionsvermögen und IR-Spektren) neu synthetisierter Dioxovanadium(V)-Komplexe der allgemeinen Formel NH₄[VO₂(L)] beschrieben, wobei L das Dianion des dreizahnigen Liganden Salicylaldehyd-thiosemicarbazon (ONS), halogensubstituiertes Salicylaldehyd- bzw. 2-Hydroxy-1-naphthaldehyd-S-methyl-isothiosemicarbazon (ONN) ist.

     

Transition metal complexes with pyrazole based ligands

The deaquation of two isostructural compounds of general formula [M(HL)₂(H₂O)₂](NO₃)₂ (M=Co, Ni, HL=3,5-dimethyl-1H-pyrazole-1-carboxamidine) is discussed in the view of their crystal and molecular structure. The compounds contain the same number and type of hydrogen bonds of the adjacent nitrate ions, only in the opposite orientation. On the basis of their deaquation pattern such a small difference may be detected, i.e., methods of thermal analysis are sensitive enough to show very small structural differences.     

Transition metal complexes with Girard reagent-based ligands

The ligand, salicylaldehyde Girard-T hydrazonium chloride, [H₂SalGT]Cl (1), and two complexes [Cu(HSalGT)X₂]·H₂O (X = Br(2); Cl(3)) were synthesized and their crystal structures were determined by single-crystal X-ray analysis. In the two isostructural complexes, the Cu(II) is located in a square-pyramidal environment, with the chelating ligand and one halogen atom in the basal plane and the second halogen in the apical position. The most apparent structural difference between the 1 and its complexes 2 and 3 is the orientation of the N(CH₃)₃ group: in 1, it is practically coplanar to the rest of the molecule, while in 2 and 3 it is oriented to the side of the axially bonded halogen, which can be explained by the C–H…X intramolecular interactions. The compounds were characterized by elemental analysis, molar conductivity, magnetic susceptibility and electronic absorption spectra.     

Transition metal complexes based on thiophene-dithiolene ligands

The chemistry of transition metal dithiolene complexes based on thiophene-dithiolene ligands (TD) is reviewed, from the ligand synthesis and complex preparation to the molecular structure and solid state physical properties of different compounds based on them. The ligands considered are based mainly either on simple thiophene-dithiolates (α-tpdt = 2,3-thiophenedithiolate, dtpdt = 4,5-dihydro-2,3-thiophenedithiolate, and tpdt = 3,4-thiophenedithiolate), or in more extended and delocalised dithiolate ligands (α-tdt = 3-({5-[(2-cyanoethyl)thio]-2-thieno[2,3-d][1,3]dithiol-2-ylidene-1,3-dithiol-4-yl}thio)propanenitrile and dtdt = 3-{5-[(2-cyanoethyl)thio]-2-(5,6-dihydrothieno[2,3-d][1,3]dithiol-2-ylidene-1,3-dithiol-4-yl)thio}propanenitrile) that besides the thiophenic ring also incorporates a fused TTF moiety. Dithiolene complexes based on ligands containing appended thiophenic units will also be briefly considered. The structural variability of these complexes that in addition to the usual square planar coordination geometry, M(TD)₂, can also present dimeric, [M(TD)₂]₂, or cluster structures such as [Cu₄(TD)₃] and [Ni₄(TD)₆], is addressed. The role of the thiophene group and its ability to enhance electronic delocalisation from the metal dithiolene core throughout the ligand and to establish solid state networks of S?S interactions is discussed. The importance of these complexes as useful building blocks to prepare molecular materials with very interesting magnetic and transport properties, ranging from metamagnets to Single Component Molecular Metals, is illustrated by different compounds based on them.     

Transition metal complexes of bidentate Schiff base ligands

New Schiff base ligands derived from vanillin (HL¹), 4-dimethylaminobenzaldehyde (HL²) and 3,5-di-t-butyl-4-hydroxybenzaldehyde (HL³) with N-(pyridyl)-3-methoxy-4-hydroxy-5-aminobenzylamine (2) and their copper(II), cobalt(II), nickel(II), oxovanadium(IV) and zinc(II) transition metal complexes have been synthesized and characterized by elemental analyses, electronic and i.r. spectra, molar conductance data and by 1H and ¹³C n.m.r. spectra. The results indicate that the ligands coordinate through azomethine nitrogen and phenolic oxygen to the metal ions. In like manner, it was found that the pyridine and amine nitrogen atoms are not coordinated to the metal ions. The ¹H and ¹³C n.m.r. spectral data confirmed the suggested structure for the Schiff base ligands, and the mass spectra results confirmed the proposed structure of the ligands. The antimicrobial activity properties of the ligands and their metal complexes have been studied.     

Transition metal chemistry of oxime-containing ligands,IX

The vibrational (conventional and far-infrared) and diffuse-reflectance spectra in conjunction with magnetic susceptibility measurements over a temperature range down to liquid nitrogen temperature are reported and discussed for the complexes; [Mn(HPOX)₂ X ₂]; [Mn(HMPX)₂ X ₂]; [Fe(HPOX)(POX) X ₂] and [Fe(HMPX)(MPX) X ₂](whereHPOX=pyridine-2-aldoxime (C₆H₆N₂O);POX=C₆H₅N₂O;HMPX=6-Methylpyridine-2-aldoxime (C₇H₈N₂O);MPX=C₇H₇N₂O;X=Cl, Br, I, NO₃, NCS, or OA c andX ₂=SO₄). On the basis of these physical studies a six-coordinated structure is suggested for the manganese(II) and iron(III) complexes.Mössbauer spectra, measured at room-temperature and liquid nitrogen temperature also indicated a six-coordinate geometry for iron(III) complexes.

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Übergangsmetallkomplexe mit Oxim-enthaltenden Liganden, IX. Spektroskopische und magnetische Untersuchungen von Mn(II)- und Fe(II)-Komplexen mit Pyridin-2-aldoxim und 6-Methylpyridin-2-aldoxim

Zusammenfassung Es wurden Komplexe von Pyridin-2-aldoxim (HPOX) und 6-Methylpyridin-2-aldoxim (HMPX) vom Typ [Mn(HPOX)₂ X ₂], [Mn(HMPX)₂ X ₂], [Fe(HPOX)(POX)X ₂] und [Fe(HMPX)(MPX)X ₂] (X=Cl, Br, I, NO₃, NCS, OA c;X ₂=SO₄) dargestellt. Die Diskussion erfolgt basierend auf Infrarot-spektroskopie (inklusive fernes IR), Messungen der magnetischen Suszeptibilität (Temp. bis zu fl. N₂) undMössbauer-Spektroskopie.

     

Transition metal chemistry of oxime containing ligands,VII

Complexes of pyridine-2-aldoxime (Hpox) with iron(II) and chromium(III) of type, [Fe(Hpox)₂ X ₂] (X=Cl, Br, I or NCS); [Cr(Hpox)₃]Cl₃·3 H₂O; [Cr(Hpox)₂ X ₂]ClO₄ (X=F, Cl or Br) and [Cr(Hpox)₂(H₂O)₂]Br₃·H₂O were prepared and characterized by analytical X-ray powder diffraction, magnetism, vibrational (conventional and far-infrared) and electronic spectroscopy techniques. X-ray and electronic spectral data indicate that all the complexes except [Cr(Hpox)₃]Cl₃·3 H₂O havetrans-pseudo-octahedral microsymmetry around the metal ion. Infrared spectral data indicate that the ligand, Hpox, behaves like a neutral ligand and coordinates to the metal ion through pyridine nitrogen atom and oxime nitrogen atom in all these complexes. The magnetic susceptibilities of chromium(III) complexes, measured over a temperature range 300–78 K, are independent of temperature whereas the magnetic moments of iron(II) complexes over a temperature range 300–20 K are dependent of temperature. The observed temperature dependence of magnetic moments of iron(II) complexes was used to evaluate the magnitude of orbital reduction factor,k, the low-symmetry distortion parameter, , and the extent of reduction in spin-orbital coupling, . In all these iron(II) complexes the magnetic results indicate the presence of an orbitally non-degenerate,⁵B_2g, ground state. Magnetically unperturbed and perturbedMössbauer spectra of iron(II) complexes at various temperatures have also been reported. Magnetically perturbedMössbauer spectra of iron(II) complexes at 4.2 K in an axial field of 60kGauss indicate that the principal component of electric field gradient tensor is positive and consistent with⁵B_2g ground electronic state in a tetragonal (D _4h) local site symmetry.

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Übergangsmetallkomplexe mit Oxim-enthaltenden Liganden, VII. Elektronische und strukturelle Eigenschaften vonFe(II)-undCr(III)-Komplexen mit Pyridin-2-aldoxim

Zusammenfassung Es wurden Komplexe von Pyridin-2-aldoxim (Hpox) mit Fe(II) und Cr(III) vom Typ [Fe(Hpox)₂ X ₂] (X=Cl, Br, I, NCS), [Cr(Hpox)₃]Cl₃·3 H₂O, [Cr(Hpox)₂ X ₂]ClO₄ (X=F, Cl, Br) und [Cr(Hpox)₂(H₂O)₂]Br₃·H₂O hergestellt. Charakterisierung und Diskussion von Geometrie und Bindungsverhalten in den Komplexen erfolgte auf Grund von analytischen Daten, Röntgen-Pulveraufnahmen, Elektronenanregungsspektroskopie, Infrarotspektroskopie, magnetischen Messungen undMössbauer-Spektroskopie.

     

Chromatography of metal chelates

Summary The chromatographic behavior of metal bis(ethoxyethyl)dithiocarbamate was investigated. The chelates of 14 elements (V, Cr, Co, Ni, Cu, Zn, Se, Mo, Cd, Te, Hg, Tl, Pb and Bi) could be preconcentrated from water with an on-line system and were shown to be suitable for C₁₈-reversed-phase liquid chromatography. A quaternary solvent mixture with admixture of a surfactant was used as eluent, UV-detection was performed at 254 nm. Thermostating the column to 40° C resulted in a significant increase in chromatographic resolution and in a decrease of analysis time. The recovery of the chelates from the aqueous solutions as well as reproducibility of the results are very sensitive to pH changes.

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Chromatographie von MetallchelatenXI. Spurenanalyse von Cadmium, Cobalt, Kupfer, Quecksilber und Nickel in Wasser mittels Bis(ethoxyethyl)dithiocarbamat als Reagens für die RP C₁₈-HPLC mit photometrischer Detektion

Zusammenfassung Das chromatographische Verhalten von Metall-bis(ethoxyl)-dithiocarbamaten wurde untersucht. Die Chelate von 14 Elementen (V, Cr, Co, Ni, Cu, Zn, Se, Mo, Cd, Te, Hg, Tl, Pb und Bi) wurden aus Wasser angereichert und anschließend direkt mittels RP C₁₈-Flüssig-Chromatographie bestimmt. Als mobile Phase diente ein quaternäres Lösungsmittelgemisch, dem ein Tensid zugesetzt wurde; Detektion fand bei 254 nm statt. Eine bemerkenswerte Steigerung der chromatographischen Auflösung sowie eine Verkürzung der Analysenzeit ergab sich aus der Thermostatisierung der Säule auf 40° C. Die Wiederfindungsrate der Chelate in wäßriger Lösung als auch die Reproduzierbarkeit der Ergebnisse wird stark durch Änderungen des pH-Werts beeinflußt.

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Part X: Häring N, Zell M, Ballschmiter K (1981) Fresenius Z Anal Chem 305:285–286

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Herrn Prof. Dr. K. H. Lieser zum 60. Geburtstag gewidmet Partly presented at the 15th International Symposium on Chromatography, Nürnberg, October 1–5, 1984     

Symmetry of metal chelates

Is a metal chelate symmetric, with the motion of the metal described by a single-well potential, or is it asymmetric, in a double-well potential? For hydrogen, this is the familiar question of the symmetry of a hydrogen bond. The molecular symmetry of MLn complexes (M = Li, Na, K, Al, Pd, Rh, Si, Sn, Ge, Sb, etc.; L is the anion of 3-hydroxy-2-phenylpropenal) in solution is now probed with the method of isotopic perturbation of equilibrium. A statistical mixture of 3-hydroxy-2-phenylpropenal-d0, -1-d, and -1,3-d2 was synthesized and converted to various metal complexes. Some complexes show two aldehydic signals, which means that their ligands are monodentate. For LiL, NaL, and KL, the 13C NMR isotope shifts, delta CH(D) - delta CH(H), for the aldehydic CH groups are small and negative, consistent with L- being a resonance hybrid. They are small and positive for AlL3, PdL2, Rh(CO)2L, SiX3L, SiL3+X-, (CF3)3GeL, SbCl4L, (EtO)4TaL, and (EtO)4NbL. The positive isotope shifts are unusual, but since they are small and temperature independent, they are intrinsic and indicate that these metal chelates are symmetric, as expected. Large positive isotope shifts, up to 400 ppb, are observed for Ph3GeL, Me3GeL, Ph2GeL2, Bu3SnL, and Ph4SbL. However, it is likely that these are monodentate complexes undergoing rapid metal migration, as judged from the X-ray crystal structures of Ph3SnL and Ph4SbL. NMR experiments indicate an intermolecular mechanism for exchange, which may be a biomolecular double metal transfer. It is remarkable that the isotope shifts in these five complexes demonstrate that they are asymmetric structures, even though they appear from other NMR evidence to be symmetric chelates.     

Transition metal chelates: Synthesis,physicochemical, thermal,and biological studies

The transition metal complex of Mn(II), Co(II), Ni(II), Cu(II), Ti(III), Cr(III), Fe(III), Zr(IV), and UO₂(VI) ion with a Schiff’s base ligand derived from 2-hydroxy-[2-oxo-1,2-dihydro-3H-indol-3-ylidene]-benzohydrazide have been prepared. The complexes have been characterized by elemental analysis data, IR and electronic absorption spectra, magnetic moments, and thermogravimetric analysis data. The complexes of the 1: 1 metal-to-ligand stoichiometry have been formed. The physico-chemical data have suggested the octahedral geometry for all the complexes except for Cu(II); the Cu(II) complex has been square planar. Thermal analysis data of the ligand and its complexes have been analyzed, and the kinetic parameters have been determined using the Horowitz–Metzger method. According to the solid-state electrical conductivity measurements, the ligand and its complexes are semiconducting in nature. The antimicrobial activity of the ligand and the complexes towards E. coli, S. typhi, P. aeruginosa, and S. aureus has been tested by the disc diffusion method.     

Mass-spectrometric determination of metal chelates

Summary A method has been developed for the determination of copper as copper acetylacetonate, making use of the copper-65 labelled chelate as internal standard. The accuracy and reproducibility in the nanogram range are comparable with those of the ligand labelling method (2% relativ). The method can be easily extended to the determination of other polyisotopic metals of which an enriched stable isotope is obtainable.

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Massenspektrometrische Bestimmung von MetallchelatenII. Quantitative Bestimmung von ng-Mengen Kupfer mit Hilfe der Isotopenverdünnungsmethode

Zusammenfassung Ein Verfahren zur Bestimmung von Nanogramm-Mengen Kupfer als Kupfer-Acetylacetonat unter Verwendung der Isotopenverdünnungsmethode mit angereichertem Kupfer-65 als Leitisotope wird beschrieben. Genauigkeit und Reproduzierbarkeit sind vergleichbar mit dem Ligandenmarkierungsverfahren (2% relativ). Das Verfahren kann leicht ausgebaut werden zur Bestimmung anderer Metalle, falls mehr als ein stabiles Isotop vorhanden ist.

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This investigation was supported in part by the Netherlands Foundation for Chemical Research (S.O.N.) with financial aid from the Netherlands Organization for the Advancement of Pure Research (Z.W.O.).     

The chromatography of metal chelates

Summary The acyl substituents of N,N-disubstituted N'-acylthioureas have a significant influence on the polarity of the chelates formed. A considerable decrease in the stability of the complexes is observed changing from aromatic to aliphatic acyl substituents. In order to separate the acylthiourea complexes, high performance thin-layer chromatography (HPTLC) methods have been used, whereby both standard methods, adsorption chromatography on silicagel layers and RP-chromatography are applicable. The strong UV-absorption properties of acylthiourea chelates allow a very sensitive detection of the separated complexes. By the method described several metals can be determined simultaneously on a migration distance of 2 to 5 cm.     

Tetranuclear planar metal clusters with two capping ligands

Background information and current research activity dealing with tetrametal planar clusters containing two capping ligands is briefly reviewed. The synthetic methods leading to these clusters and their chemical properties are presented. The structure and bonding in lo some representative example is discussed. Their application as models of heterogeneous catalysts, homogeneous catalysts, and precursors to materials is highlighted. Such information can have important implications in the design of a more sophisticated tetranuclear cluster systems for improved process applications.