Biuret complexes of divalent transition metals.

The complexes M bi₂ X₂ with M = Mn, Co, Ni and Cu, X = Cl, Br and I have been prepared. IR spectra and magnetic properties are given. The analysis of the ligand field parameters obtained from the electronic spectra for the cobalt and nickel compounds are in agreement with a trans octahedral structure.     

Transition metal complexes of 2-thenoyltrifluoroacetone isonicotinoyl hydrazone

Summary 2-Thenoyltrifluoroacetone isonicotinoyl hydra/one (H₂L), made by condensation of 2-thenoyltrifluoroacetone(TTA) with isonicotinic acid hydrazide, and its transition metal complexes were prepared. H₂L functions as a tetradentate ligand for divalent metal ions, but as a tridentate ligand for trivalent metal ions, taking part in coordination in both mono- and divalent anions. Antioxidative tests were made to examine the elimination action for H₂L and the complexes towards superoxide O _inf2 ^sup–. and hydroxyl OH^. radicals, which confirmed the efficient antioxidative action towards these radicals.     

Synthesis and structural studies of some first row transition metal complexes of acetone isonicotinoyl hydrazone

Acetone isonicotinoyl hydrazone (AINH) has been found to form complexes of the types MCl₂·AINH·nEtOH and M(AINH-H)₂·nH₂O where M  Mn(II), Fe(II), Co(II), Ni(II), Cu(II) or Zn(II) and n  0, 1 or 2. Cu^ICl·AINH has also been prepared starting with Cu(II) chloride. All the complexes are found to be non-electrolytes in pyridine. Tentative structural conclusions are drawn for these complexes based upon electronic spectral and room-temperature magnetic measurements. IR spectral studies suggest that AINH functions as a bi- or tridentate ligand in the complexes of the former type and as a tridentate one in the latter type of complexes. The positions of the v(M-O) mode in the low frequency IR spectra of the complexes have been correlated with their overall stability constants, log K.     

Trimellitate complexes of divalent transition metals with hydrazinium cation

New dihydrazinium divalent transition metal trimellitate hydrates of empirical formula (N₂H₅)₂M(Html)₂·nH₂O, where n = 1 for M = Co or Ni, and n = 2 for M = Mn, Zn, or Cd (H₃tml = trimellitic acid), and monohydrazinium cadmium trimellitate, [(N₂H₅)Cd(Html)_1.5·2H₂O] have been prepared and characterized by physico-chemical methods. Electronic spectroscopic, and magnetic moment data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of monodentate carboxylate anion (Δν = ν_asy(COO^?) ? ν_sym(COO^?) > 190 cm^?1) and coordinated N₂H₅ ⁺ ion (ν_N–N 1015 ? 990 cm^?1) in all the complexes. All the complexes undergo endothermic decomposition eliminating CO₂ in the temperature region 200–250 °C, followed by exothermic decomposition (in the range of 500–570 °C) of organic moiety to give the respective metal carbonate as the end products except nickel and cobalt complexes, which leave respective metal oxides. X-ray powder diffraction patterns reveal that Ni and Co complexes are isomorphous as are those of, Zn(II) and Cd(II) of the type, (N₂H₅)₂M(Html)₂·2H₂O.     

Macrocyclic complexes of transition metals with divalent polyaza units

A new series of 14–16-membered hexaazamacrocyclic complexes [ML¹X₂] and [ML²X₂] (M = Co^II, Ni^II, Cu^II and Zn^II; X = Cl or NO₃) have been synthesized by template condensation of phenylenediamine, primary diamines and formaldehyde solution 35% in MeOH and have been characterized by i.r., 1H-n.m.r., e.p.r., and u.v. spectroscopy as well as by magnetic susceptibility and conductivity measurements. An octahedral geometry has been suggested for all the complexes.     

Structural elucidation of o-vanillin isonicotinoyl hydrazone and its metal complexes

Summary A new series of complexes with the tridentate dibasic Schiff base ligand o-vanillin isonicotinoyl hydrazone (o-VINH) were prepared and characterized by i.r., ¹H n.m.r. and electronic spectral studies, magnetic susceptibility measurements and t.g.a. The disappearance of low field signals due to OH, NH protons at 10.23 and 9.31 p.p.m. and downfield shift of the –CH=N proton signal at 8.17 p.p.m. in the n.m.r. spectrum confirms the involvement of these groups in coordination. Both t.g.a. and i.r. spectral data show evidence for one molecule of coordinated H₂O. These results taken in conjunction with electronic spectral data allow assignation of tetrahedral geometry for manganese(II), nickel(II) and palladium(II) complexes but a square planar configuration to cobalt(II), copper(II) amd zinc(II) complexes.     

Structural studies on new copper(II) phenylhydrazoacetylacetone isonicotinoyl hydrazone complexes

Summary Copper(II) phenylhydrazoacetylacetone isonicotinoyl hydrazone complexes were prepared at two different pHs and characterized by elemental analysis and various physical techniques. In neutral solutions monoligand complexes (1) and (2) were obtained, but the bisligand complex (3) was obtained from solution at pH 10. The ligand H₂L behaved either as monobasic bidentate or dibasic tridentate towards cupric ions. Magnetic and spectral data suggest square planar structures for [CuL·H₂O]·H₂O but an octahedral structure for [Cu(HL)₂·2H₂O]·3H₂O.Author to whom all correspondence should be directed.     

Spectrophotometric and solvent extraction study of o-hydroxybenzaldehyde isonicotinoyl hydrazone complexes with gallium and indium

Complex formation of o-hydroxybenzaldehyde isonicotinoyl hydrazone with Ga^III, In^III and Tl^III has been studied. The thallium complex is unstable. The composition and the instability constants of gallium and indium complexes were determined. Molar absorptivity of gallium complex at 390 nm is 3.40 × 10⁴ and that of indium at 380 nm is 3.20 × 10⁴ l mole^?1 cm^?1. Both complexes were found to be rapidly and quantitatively transfered into 1-pentanol. The corresponding aluminum complex is not extracted. Possible analytical application for separation and spectrophotometric determination of these elements is also examined.     

Synthesis and characterization of new complexes of some divalent transition metals with 2-acetyl-pyridyl-isonicotinoylhydrazone

Ten new mononuclear complexes having general formulae [ML₂](ClO₄)₂, M = Cu(II), Co(II), Ni(II), Mn(II) and Zn(II), [ML₂](SO₄), M = Co(II), Ni(II) and [ML₂(H₂O)₂](SO₄), M = Cu(II), Mn(II) and Zn(II), L = 2-acetyl-pyridyl-isonicotinoylhydrazone have been synthesized and characterized based on elemental analyses, IR spectroscopy, UV–Vis–NIR, EPR, as well as thermal analysis and determination of molar conductivity and magnetic moments. The structures of [CoL₂](ClO₄)₂ are accomplished by single crystal X-ray diffraction. The coordination sphere is formed by two N, N, O tridentates 2-acetyl-pyridyl-isonicotinoylhydrazone ligands, or by two N, O bidentate 2-acetyl-pyridyl-isonicotinoylhydrazone and two water molecules. Biological activity studies reveal a moderate activity of complexes against gram-negative and gram-positive bacteria.     

Norbornadiene complexes of transition metals

Conclusions Correlations were established between the stereochemistry of 2-(-carbinol)norbornadiene complexes of rhodium and their mass spectra.This study is also communication 30 from the series Mass Spectrometry of Transition Metal- Complexes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2701–2703, December, 1982.     

Thermodecomposition ofo-benzoquinone complexes of transition metals

Thermodecomposition of 3,5- and 3,6-di-tert-butyl-o-benzoquinone complexes of Cu, Fe, Co, Cr, Mo, and W has been investigated in the solid phase by the thermogravimetric method. The relative stability of a series of complexes has been determined from the temperatures at which their decomposition begins. Detachment of a neutral electron-donor ligand takes place in the first stage. Detachment of ano-quinone ligand and decomposition of theo-benzoquinone formed occur in the next stage. Thermodecomposition of Fe, Co, Cr, Mo, and W complexes gives oxides or carbides, while copper complexes decompose to pure metal.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 327–329, February, 1994.     

Dihydrogen complexes of the transition metals

Summary The binding and activation of dihydrogen by simple transition metal complexes is of fundamental importance in processes as diverse as the homogeneous or heterogeneous hydrogenation of unsaturated organic molecules⁽¹⁾ and understanding how metalloenzymes such as nitrogenase⁽²⁾ and the hydrogenases⁽³⁾ work at the atomic level.Simple consideration of the oxidative-addition of dihydrogen to a coordinatively-unsaturated complex {or its reverse (reductive-elimination)} reveals that the reactions are compelled to proceed via a dihydrogen complex as shown in Equation (1). However until recently it was considered that the dihydrogen complex had only a fleeting existence. Although there had been some reports in the literature such as that by Ashworth and Singleton⁽⁴⁾ that the formally Ru^IV trihydride, [RuH₃(PMe₂Ph₂]⁺ was better formulated as the Ru¹¹ species [RuH(H₂)(PMe₂Ph)₂]⁺, these could not be substantiated. In 1984, though, Kubas showed that the apparently innocuous complex [WH₂(CO)₃(PPr ₃ ⁱ )₂] contained the side-on bonded dihydrogen molecule, established unambiguously by x-ray, and neutron crystallography and spectroscopy⁽⁵⁾. In this highlight the current status of dihydrogen complexes, their structure, identification and in particular their reactivity will be discussed.     

Synthesis and characterization of the complexes of some transition metals with 2-acetyl pyridine (N-benzoyl) glycyl hydrazone

Complexes of Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) with 2-acetyl pyridine (N-benzoyl) glycyl hydrazone(2-ApBzGH) have been synthesized and characterized by elemental analyses, molar conductances, magnetic susceptibility, IR, electronic, ESR,¹H,¹³C and¹¹³Cd NMR spectral and X-ray diffraction studies. IR and NMR data suggest the tridentate nature of the ligand coordinating as a neutral species in the addition complexes and as a uninegative species in the deprotonated complexes. The presence of more than one isomer of the ligand has been established by¹H NMR spectra of the ligand and complexes recorded over the 298–396 K range. The X-ray powder diffraction patterns of [Cd(2-ApBzGH)Cl]Cl and [Cu(2-ApBzGH)Cl(H₂O)₂]Cl are indexed for orthorhombic and tetragonal crystal systems respectively.     

Synthetic and physicochemical studies of divalent metal complexes with cyclic hydrazone and semicarbazone ligands

Summary The syntheses of 3,4,10,11-tetraphenyl-1,2,5,6,8,9,12,13-octaazacyclotetradeca-7, 14-dione-2,4,9,11-tetraene (dbdch) and 6-methoxy-1,6-diphenyl-4-oxo-3,4,5,6-tetrahydro-2,3,5-triazine (bsc) and their complexes with divalent metal ions (copper, nickel, cobalt, zinc, cadmium and mercury) are reported. All compounds were characterized by ¹H n.m.r., ¹³C n.m.r., i.r. and u.v.-vis. spectroscopy and by FAB mass spectrometry; possible structures are presented and discussed.Author to whom all correspondence should be directed.     

Acetone picolinoyl hydrazone complexes of some first row transition metal ions

Summary Acetone picolinoyl hydrazone (APH) complexes of the types M(APH)Cl₂nEtOH and M(APH-H)₂2EtOH (where M = manganese(II), iron(II), cobalt(II), nickel(II), or copper(II); n = 0 or 2) have been prepared and their nature and structures studied by molar conductance, molecular weight determination, thermal degradation, magnetic susceptibility, electronic and i.r. spectral measurements. Spin-free octahedral geometry has been proposed for all the complexes except Mn(APH)Cl₂ and Co(APH)Cl₂ for which tetrahedral geometry has been suggested.