Formation of nitridotechnetium (VI) μ-oxo dimer complexes with EDTA and EDDA

Reactions of [⁹⁹TcNCl₄]^– with ethylenediaminetetraacetic acid (EDTA) and ethylenediamine-N, N-diacetic acid (EDDA) in a mixture of water and acetone gave Tc^VIN-EDTA and Tc^VIN-EDDA complexes. The infrared spectra of both reaction products showed the existence of the TcN and C=O groups. The elemental analysis indicated the 11 TcN-ligand ratio in the EDTA and EDDA complexes. Electrophoresis showed that the Tc^VI-EDTA complex was an anionic species in a perchlorate solution. For the Tc^VIN-EDDA complex, neutral and anionic species were formed, depending on the pH of the solution. Formation of the -oxo dimer complexes was suggested from the UV-Vis absorption spectra.     

Binuclear cationic μ-bromo complexes of vanadium(II)

The compounds [V₂(μ-Br)₃L₆]BPh₄, with L = 3-methyltetrahydrofuran (1) and tetrahydrofuran (2), have been prepared. The crystal and molecular structures of 1 have been determined. The compound crystallizes in space group Cc with unit cell dimensions a = 18.499(3), b = 10.923(3), c = 29.619(7) Å, β = 103.18(2)^o, V = 5827(5) ų and Z = 4. The [V₂(μ-Br)₃(CH₃C₄H₇O)₆]⁺ ion is analogous to the [V₂(μ-Cl)₃L₆]⁺ cations previously described, but has a longer V—V distance, viz. 3.146(4) A. The UV-vis spectrum shows a double spin-flip transition but it is extremely weak compared to that in the chloro analog. Qualitatively, this was expected because of the ca 0.16 Å increase in the V—V distance, but the magnitude of the decrease (∼ 5 fold) is of interest.     

Fluoro complexes of hexavalent uranium—V: Fluorooxalato complexes of dioxouranium(VI)

The salts of the new types M₂[UO₂F₂(C₂O₄)], M₄[UO₂F₂(C₂O₄)₂] and M₂[(UO₂)₂F₄(C₂O₄)] (where M = potassium and rubidium) have been prepared by mixing saturated solutions of H[UO₂F₃]·H₂O with alkali metal oxalate solutions in cold in different mole ratios. Molecular conductances of the salt solutions indicate that the ions are decomposed in dilute solution to a great extent. The complexes are also completely decomposed on passing their solutions through a column of cation exchange resin in hydrogen form. The IR spectra of the salts of [UO₂F₂(C₂O₄)]²⁻ and [UO₂F₂(C₂O₄)₂]⁴⁻ indicate that oxalate is acting as a normal chelating agent, while the spectra of the salts of [(UO₂)₂F₄(C₂O₄)]²⁻ support that the ion contains bridged oxalate group. The lattice parameters of the three potassium salts have been reported.     

Fluoro complexes of hexavalent uranium—VII: Fluorosulphato complexes of dioxouranium(VI)

The fluorosulphato complexes K₂[U0₂F₂(S0₄)], (NH₄)₂[U0₂(S0₄)], (NH₄)₆[(UO₂)₂F₄(SO₄)₃] and Cs₂[(U0₂)₂F₄(S0₄)] have been prepared by crystallising solutions containing U0₂F₂ and ammonium or the alkali metal sulphates. Another ammonium salt, (NH₄)[U0₂F(S0₄)] has been obtained by the pyrolysis of (NH₄)₂F₂(S0₄)]. Molecular conductance and ion exchange studies show that the complex ions are decomposed in dilute solution. The IR spectra of the complexes indicate that the sulphate ion acts as a bidentate chelating or briged bidentate group C_2v symmetry of sulphate ion The lattice parameters of the potassium and ammonium salts have been reported.     

Synthesis of enantiopure β-amino alcohols via AKR/ARO of epoxides using recyclable macrocyclic Cr(III) salen complexes

A series of chiral macrocyclic Cr(III) salen complexes 1-8 were synthesized and characterized. These complexes were found to be highly active, regio-, diastereo-, and enantioselective catalysts in aminolytic kinetic resolution (AKR) of racemic trans-epoxides as well as asymmetric ring opening (ARO) of prochiral meso-epoxides with various anilines as nucleophiles at room temperature in 18-24 h. Excellent yields (>99% with respect to the nucleophile) with high enantioselectivity (ee, >99%) of chiral anti-β-amino alcohols was achieved with concomitant recovery of corresponding epoxides in high ee (up to >99%). The complex 1 also catalyzed the ARO of meso-epoxides to provide corresponding syn-β-amino alcohols in high yield (99%) and ee (up to 91%). Due to built-in basic sites in the catalyst, no external base (as an additive) was required to promote AKR and ARO reactions. The catalyst 1 was conveniently recycled several times with retention of its performance. The AKR of trans-stilbene oxide with aniline was successfully demonstrated at relatively higher scale (10 mmol) using the catalyst 1.     

Photophysical studies of uranyl complexes—VI. Luminescence spectra of bis(imidazolium) tetrachlorodioxouranate(VI) and bis(2-methylimidazolium) tetrachlorodioxouranate(VI)

The photoluminescence spectra of the title compounds have been studied under conditions of high resolution at cryogenic temperatures. The luminescence obtained from the 2-methyl imidazolium salt was found to be well behaved, in that all emission originated from intrinsic uranyl centers and all luminescence decay curves consisted of single exponentials. In contrast, the emission associated with the imidazolium salt was found to originate both from intrinsic uranyl groups and from luminescence traps. The analysis of the luminescence decay curves obtained at cryogenic temperatures revealed that the lifetimes characteristic of the trap emission were significantly shorter than those associated with the intrinsic luminescence. The magnetic dipole allowed origins were found to be split by the rhombic crystal field in each system, but this splitting was observed to be 11 cm⁻¹ or less. All other features present in either spectrum were assigned as vibronic in nature and they represent coupling of the various O-U-O or U-Cl vibrational modes with the pure electronic origins.     

Nucleotide hydrolysis in the presence of μ-hydroxo-bridged-cobalt(III) complexes

Abstract

Two cobalt(III) complexes with tridentate ligands, the acyclic diethylenetriamine and macrocyclic 1,4,7-triazacyclononane, were examined as potential catalysts for the hydrolysis of adenosine 5′-triphosphate (ATP). Studies were performed primarily at pH 4.5, where the two complexes were in the binuclear di-μ-hydroxo forms. For both complexes, a rapid initial hydrolysis with first order dependence on the concentration of ATP was observed, k_obs of approximately 0.20 min^?1, followed by very slow hydrolysis. Deuterium isotope studies done in D₂O showed a normal isotope effect with k_H/k_D = 1.8. Spectral investigations and ⁵⁹Co NMR studies indicated that the biphasic nature of the hydrolysis reaction may be due to the formation of a complex in which inorganic phosphate is coordinated to the cobalt, effectively poisoning the catalyst.     

Synthesis and magnetism of μ-isophthalato dinuclear lanthanide(Ⅲ) complexes

Seven new μ-isophthalato dinuclear lanthanide(Ⅲ) complexes, namely [Ln2(IPHTA)(Me2-phen)4-(ClO4)2](ClO4)2 (Ln = La, Nd, Sm, Eu, Gd, Ho, Er), where Me2-phen denotes 2,9-dimethyl-1, 10-phenanthroline (Me2-phen) , IPHTA represents isophthalate dianion, have been synthesized and characterized by elemental analyses, molar conductance measurements, IR, ESR and electronic spectra. The variable-temperature magnetic susceptibilities of [Gd2( IPHTA) (Mez-phen)4 (ClO4)2] (ClO4)2 complex were measured in the temperature range of 4-300 K and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, H = - 2JS1 · S2, giving the exchange parameter J =- 0.19 cm-1 . This result is commensurate with a weak antiferromagnetic spin-exchange interaction between Gd(Ⅲ)-Gd(Ⅲ) ions within the complex.     

Recovery of tungsten(VI) and molybdenum(VI) with N′,N′-dialkylhydrazides of aliphatic carboxylic acids from acid solutions

Russian Journal of Applied Chemistry - Recovery of tungsten(VI) with solutions of N′,N′-dialkylhydrazides of 2-ethylhexanoic and octanoic acids in kerosene from sulfuric acid and...     

Thermodynamics of the Extraction of U(VI) by N,N′-Didecanoylpiperazine

A novel extractant, N, N-didecanoylpiperazine (DDPEZ), was synthesized for the first time. The extraction of U(VI) by DDPEZ from aqueous nitric acid media in carbon tetrachloride has been studied. The dependence of extraction distribution ratio on concentration of aqueous nitric acid, extractant, salting-out agent and temperature was investigated and the enthalpy of the extraction was calculated.     

Fluoro complexes of hexavalent uranium—VI adducts of dioxodifluorouranium (VI) with nitrogen and oxygen donor ligands

Adducts of uranyl fluoride of the types UO₂F₂·L·H₂O and UO₂F₂·L′ (where L = 2,2′-dipyridyl, 1, 10-phenathroline and 8-hydroxyquinoline; L′ = dimethyl sulphoxide, dimethyl formamide, pyridine, α-picoline and γ-picoline) have been prepared by mixing uranyl fluoride and the corresponding ligand in 1:1 mole ratio in 50% aqueous ethanolic medium. Two adducts with urea, viz. [UO₂F₂(urea)] and [UO₂F₂(urea)₂] have been obtained by reacting uranyl fluoride with urea in different mole ratios in dry methanolic medium. The molecular conductances of the complexes in methanol indicate their nonelectrolytic nature. IR spectral studies show that urea, dimethyl formamide and dimethyl sulphoxide complexes are oxygen bonded ones. Thermogravimetric analysis suggests that the dipyridyl, phenanthroline and oxine complexes contain coordinated water.     

Metal site electronic structure of μ-dithioterephthalato copper(II) binuclear complexes

The preparation and spectroscopic study of three homobinuclear complexes of Cu(II) with dithioterephthalic bisanion. DTTA, formulated as [(μ-DTTA)Cu₂(am)₂](ClO₄)₂, where am=aromatic diamine, is discussed. The instability of the compounds and the results of the spectral studies are in support of a polymeric structure with a local planar CuN₂S₂ chromophore.     

Synthesis and magnetism of μ-1,3,5-benzenetricarboxylatocopper(II) trinuclear complexes

Summary Three new Cu^II trinuclear complexes, namely [Cu₃(BZT)(phen)₃(ClO₄)₃]·6H₂O (1), [Cu₃(BZT)(Nphen)₃ (ClO₄)₃]·6H₂O (2) and [Cu₃(BZT)(bipy)₃ (ClO₄)₃]·3H₂O (3) (BZT) = 1,3,5-benzenetricarboxylato, phen = 1,10-phenanthroline, Nphen = 5-nitro-1,10-phenanthroline, bipy = 2,2-bipyridyl, have been synthesized, with 1,3,5-benzenetricarboxylato as the bridged ligand, and characterized by elemental analysis, and i.r. and electronic reflection spectra. We propose that the complexes have an extended 1,3,5-benzenetricarboxylatobridged structure containing three Cu^II atoms. The variable-temperature magnetic susceptibilities of the complexes were measured in the 77–300 K range. The magnetic coupling parameters are consistent with an antiferromagnetic exchange model based on the Hamiltonian operator [=–2J( _{1 2}+ _{1 3}+ _{2 3}, where S ₁=S ₂=S ₃=1/2, giving the antiferromagnetic coupling parameters of 2J = – 18.6 cm^-1 for (1)–(3).     

Use of ESR for characterizing exchange-coupled polynuclear μ-oxo complexes of iron(iii)

ESR spectra of 13 bi-, tri- and tetranuclear -oxo complexes of Fe(III) were studied in the solid state and in solution. On the basis of the data obtained, the broad signal observed nearg=2 for all the complexes was interpreted as resulting from thermal populating of paramagnetic excited states.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 470–472, March, 1993.     

Alkylimido osmium(VI) and ruthenium(VI) porphyrins. Crystal and molecular structures of Os(TTP)(O)(NBu~t)·EtOH and Os(4-Cl-TPP)(NBu~t)_2

Oxo(tert-butylimido) or bis(tert-butylimido)osmium(VI) porphyrins Os(Por)(O)(NBut) and Os(Por)(NBut)2, [Por=meso-tetrakis(p-tolyl)porphyrinato (TTP) and meso-tetrakis(4-chlorophe-nyl)porphyrinato (4-Cl-TPP)] were synthesized by air oxidation of bis(tert-butylamme)osmium(II) porphyrins [Os(Por)(H2NBut)2 (Por=TPP, 4-Cl-TPP], depending on whether tert-butylamine is present. The bis(tert-butylamine)ruthenium(II) porphyrins [Ru(Por)(H2NBut)2, Por=TTP, 4-Cl-TPP] can undergo bromine oxidation to give oxo(tert-butylimido)ruthenium(VI) complexes in quantitative yields. All these new complexes were characterized by 1H NMR, UV-Visible and IR spectroscopy. The X-ray crystal structures of Os(TTP)(O)(NBut).EtOH and Os(4-Cl-TPP)(NBut)2 have been determined. Crystal data: for Os(TTP)(O)(NBut).EtOH: monoclinic, space group P21/c, a=1.3546(6) nm, b=2.3180(3) nm, c=1.6817(3) nm, B=90.84(2), V=527.97(1) nm3, Z=4. The Os=O and Os=NBut distances in Os(TTP)(O)(NBut).EtOH are 0.1772(7) nm and 0.1759(9) nm, respectively. The av     

The synthesis of thionitrosodimethylamine (Me2NNS) complexes of ruthenium,osmium, and iridium

Neutral hydrido complexes [ML]ClH(PPh₃)₃ ([ML] = Ru(CO), Os(CO) and Ir(Cl)] react with thionitrosodimethylamine, Me₂NNS, to give [ML]ClH-(SNNMe₂)(PPh₃)₂ with H trans to Me₂NNS, while the hydrido cations cis,trans-[[ML]H(SNNMe₂)₂(PPh₃)₂]⁺ are obtained from Me₂NNS and [Ru(NCMe)₂(CO)-(PPh₃)₂]⁺, [OsH(OH₂)(CO)(PPh₃)₃]⁺ and [IrClH(NCMe)₂(PPh₃)₂]⁺, respectively. The coordinatively unsaturated aryl complexes [ML′]Cl(p-tolyl)(PPh₃)₂ ([ML′]Ru(CO), Os(CO) and Os(CS)) coordinate one molecule of Me₂NNS to give [ML′]Cl(p-tolyl)(SNNMe₂)(PPh₃)₂, the chloride ligands of which are labile. Spectroscopic data suggest that in all these complexes the Me₂NNS ligand adopts a η¹(S) coordination mode.     

2-(2′-Pyridyl) benzimidazole complexes of dioxouranium(VI) and thorium(IV)

The bidentate ligand, 2-(2′-pyridyl) benzimidazole (PBH), forms a variety of complexes with dioxouranium(VI) and thorium(IV) of the type, UO₂(PBH)_xX₂ (n = 1, X = Cl, I, NO₃, 0.5SO₄; n = 2, X = NCS), UO₂(PBH)₃(ClO₄)₂, Th(PBH)₂X₄=Cl, NCS, NO₃) and Th(PBH)₄(ClO₄)₄. Microanalysis, electrical conductivity in various non-aqueous media, electronic and IR (down to 200 cm⁻¹) spectra, mass spectra and the TGA, DTA measurements on the complexes are reported.     

Syntheses of (imidazole)pentaamminemetal(III) and μ-imidazolatodecaamminedimetal(III) complexes from trifluoromethanesulfonato precursors

The [M(NH₃)₅(imidH)]³⁺ complex ions (M = Co, Rh or Ir; imidH = imidazole) can be readily prepared by reaction of [M(NH₃)₅(OSO₂CF₃)]²⁺ ions with imidazole in sulfolane. Subsequent reaction of [M′(NH₃)₅(OSO₂CF₃)]²⁺ with [M(NH₃)₅(imidH)]³⁺ in sulfolane in the presence of a non-coordinating base permits synthesis of the binuclear imidazolate-bridged complexes [(NH₃)₅M(imid)M′(NH₃)₅]⁵⁺ (M = M′= Co or Rh; M = Co, M′ = Rh), characterized by spectroscopic, chromatographic and voltammetric methods, and by reactivity.     

Iron-catalyzed alkenylation of cyclic ethers via decarboxylative sp(C)–sp(C) coupling

An efficient Fe(acac)₃-catalyzed decarboxylative C(sp²)–C(sp³) coupling reaction via oxidation of C–H bond adjacent to an oxygen atom has been developed successfully, in which cyclic ethers are selectively transformed into the corresponding alkenylation products with good chemical yields and excellent stereoselectivities. The mechanism was studied and the reaction was supposed to proceed through a radical oxidative coupling process.