Potentiometric determination of Ca(II), Nd(III) and Pu(III) chelates formed by diethylenetriaminepentaacetic acid

A method for direct analysis of the curves of potentiometric (pH) measurements of equimolar M^z++H_nL chelating systems has been worked out. It is based on the balance of ionic charges and the mass balances of metal ion, ligand and hydrogen. The results of the study of Ca(II), Nd(III) and Pu(III) chelates with DTPA are given.     

Synthesis and magnetic resonance of new heteropolynuclear Ln(III)-Cu(II) complexes with noncyclic polyether Schiff base

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Synthesis,characterization and crystal structures of cyclometallated Ru(II) carbonyl complexes formed by hydrazones

Cyclometallated Ru(II) complexes of the type [Ru(CO)(EPh₃)₂(L)] (E = P or As; L = tridentate hydrazone-derived ligand) have been obtained by refluxing an ethanolic solution of [RuHCl(CO)(PPh₃)₃] or [RuHCl(CO)(AsPh₃)₃] with the hydrazone derivatives H₂php (2-[(2,4-dinitro-phenyl)-hydrazonomethyl]-phenol), H₂phm (2-[(2,4-dinitro-phenyl)-hydrazonomethyl]-6-methoxy-phenol) and H₂phn (2-[(2,4-dinitro-phenyl)-hydrazonomethyl]-naphthalen-1-ol). The formation of stable cyclometallated complexes has been authenticated by single crystal X-ray structure determination of two of the complexes, and the mechanism of C–H activation is discussed in detail. The spectral (IR, UV–Vis and ¹H NMR) and electrochemical data for all the complexes are reported. Electrochemistry shows a substantial variation in the metal redox potentials with regard to the electronic nature of the substituents present in the hydrazone derivative.     

Iron(II) and iron(III) complexes containing ethynyl thiophene fragments

The synthesis of the new complexes Cp*(dppe)FeCC2,5-C₄H₂SR (Cp* = 1,2,3,4,5-pentamethylcyclopentadienyl; dppe = 1,2-bis(diphenylphosphino)ethane; 2a, R = CCH; 2b, R = CCSi(CH₃)₃; 2c, R = CCSi(CH(CH₃)₂)₃; 3a, R = CC2,5-C₄H₂SCCH; 3c, R = CC2,5-C₄H₂SCCSi(CH(CH₃)₂)₃) is described. The ¹³C NMR and FTIR spectroscopic data indicate that the π-back donation from the metal to the carbon rich ligand increases with the size of the organic π-electron systems. The new complexes were also analyzed by CV and the chemical oxidation of 2a and 3c was carried out using 1 equiv of [Cp₂Fe][PF₆]. The corresponding complexes 2a[PF₆] and 3c[PF₆] are thermally stable, but 2a[PF₆] was too reactive to be isolated as a pure compound. The spectroscopic data revealed that the coordination of large organic π-electron systems to the iron nucleus produces only a weak increase of the carbon character of the SOMO for these new organoiron(III) derivatives.     

Discrete Rh(III)/Fe(II) and Rh(III)/Fe(II)/Co(III) cyanide-bridged mixed valence compounds

The heterotrinuclear complexes trans- and cis-[{cis-VI-L(15)Rh(III)(μ-NC)}{trans-III-L(14S)Co(III)(μ-NC)}Fe(II)(CN)(4)](2+) are unprecedented examples of mixed valence complexes based on ferrocyanide bearing three different metal centers. These complexes have been assembled in a stepwise manner from their {trans-III-L(14S)Co(III)}, {cis-VI-L(15)Rh(III)}, and {Fe(II)(CN)(6)} building blocks. The preparative procedure follows that found for other known discrete assemblies of mixed valence dinuclear Cr(III)/Fe(II) and polynuclear Co(III)/Fe(II) complexes of the same family. A simple slow substitution process of [Fe(II)(CN)(6)](4-) on inert cis-VI-[Rh(III)L(15)(OH)](2+) leads to the preparation of the new dinuclear mixed valence complex [{cis-VI-L(15)Rh(III)(μ-NC)}Fe(II)(CN)(5)](-) with a redox reactivity that parallels that found for dinuclear complexes from the same family. The combination of this dinuclear precursor with mononuclear trans-III-[Co(III)L(14S)Cl](2+) enables a redox-assisted substitution on the transient {L(14S)Co(II)} unit to form [{cis-VI-L(15)Rh(III)(μ-NC)}{trans-III-L(14S)Co(III)(μ-NC)}Fe(II)(CN)(4)](2+). The structure of the final cis-[{cis-VI-L(15)Rh(III)(μ-NC)}{trans-III-L(14S)Co(III)(μ-NC)}Fe(II)(CN)(4)](2+) complex has been established via X-ray diffraction and fully agrees with its solution spectroscopy and electrochemistry data. The new species [{cis-VI-L(15)Rh(III)(μ-NC)}{trans-III-L(14S)Co(III)(μ-NC)}Fe(II)(CN)(4)](2+) and [{cis-VI-L(15)Rh(III)(μ-NC)}Fe(II)(CN)(5)](-) show the expected electronic spectra and electrochemical features typical of Class II mixed valence complexes. Interestingly, in the trinuclear complex, these features appear to be a simple addition of those for the Rh(III)/Fe(II) and Co(III)/Fe(II) moieties, despite the vast differences existent in the electronic spectra and electrochemical properties of the two isolated units.     

Synthesis, structures and properties of hydrolytic Al(III) aggregates and Fe(III) analogues formed with iminodiacetate-based chelating ligands

Both Al(III) and Fe(III) display a rich hydrolytic chemistry which can lead to the formation of a variety of aggregated oxo and hydroxo-bridged aggregates. The formation, structures and properties of these species are important in defining the availability and reactivity of these species in aqueous environments such as are found in biological systems and the environment. Although there are many similarities in the behaviour of the Al³⁺ and Fe³⁺ ions there are also some important differences between these two metal ions which can lead to a divergence in their chemistries. These considerations are discussed and illustrated with reference to 16 Al(III) and Fe(III) compounds, which have been crystallographically characterised, and which form in aqueous environments in the presence of chelating ligands containing the iminodiacetate functionality.     

Chromium(II) and chromium(III) complexes supported by tris(2-pyridylmethyl)amine: synthesis, structures, and reactivity

This report describes the synthesis, structural characterization, and polymerization behavior of a series of chromium(II) and chromium(III) complexes ligated by tris(2-pyridylmethyl)amine (TPA), including chromium(III) organometallic derivatives. For instance, the combination of TPA with CrCl(2) yields monomeric (TPA)CrCl(2) (1). A similar reaction of CrCl(2) with TPA, followed by chloride abstraction with NaBPh(4) or NaBAr(F)(4) (Ar(F) = 3,5-(CF(3))(2)C(6)H(3)), provides the weakly associated cationic dimers [(TPA)CrCl](2)[BPh(4)](2) (2A) and [(TPA)CrCl](2)[BAr(F)(4)](2) (2B), respectively. X-ray crystallographic analysis reveals that each chromium(II) center in 1, 2A, and 2B is a tetragonally elongated octahedron; such Jahn-Teller distortions are consistent with the observed high spin (S = 2) electronic configurations for these chromium(II) complexes. Likewise, reaction of CrCl(3)(THF)(3) with TPA, followed by anion metathesis with NaBPh(4) or NaBAr(F)(4), yields the monomeric, cationic chromium(III) complexes [(TPA)CrCl(2)][BPh(4)] (4A) and [(TPA)CrCl(2)][BAr(F)(4)] (4B), respectively. Treatment of 4A with methyl and phenyl Grignard reagents produces the cationic chromium(III) organometallic derivatives [(TPA)Cr(CH(3))(2)][BPh(4)] (5) and [(TPA)CrPh(2)][BPh(4)] (6), respectively. Similar reactions of 4A with organolithium reagents leads to intractable solids, presumably due to overreduction of the chromium(III) center. X-ray crystallographic analysis of 4A, 5, and 6 confirms that each possesses a largely undistorted octahedral chromium center, consistent with the observed S = (3)/(2) electronic ground states. Compounds 1, 2A, 2B, 4A, 4B, 5, and 6 are all active polymerization catalysts in the presence of methylalumoxane, producing low to moderate molecular weight high-density polyethylene.     

Formation of heteropolynuclear cobalt(II) and nickel(II) complexonates with EDTA and 2-aminopropanoic acid

Coordination equilibria in the Co(II)–Ni(II)–2-aminopropanoic acid (HAla)–EDTA system have been studied spectrophotometrically at different molar ratios of the reagents in a wide pH range. It has been found that, when metal ions are in excess with respect to EDTA at pH 5–9, polyheteronuclear complexonates [(CoAla)Edta(NiAla)]^2–, [(CoAla₂)Edta(NiAla₂)]^4–, [(NiAla₂)Edta(CoAla₂)₂]^4–, [(CoAla₂)Edta(NiAla₂)₂]^4–, and [(NiAla₂)₂Edta(CoAla₂)₂]^4– form in a solution. The equilibrium constants of formation of these complexes and their overall stability constants have been calculated. Possible structures of the polynuclear complexonates are discussed.     

Syntheses, structures, and magnetic properties of mixed-valent diruthenium(II,III) diphosphonates with discrete and one-dimensional structures

Four mixed-valent ruthenium diphosphonates, namely, Na(4)[Ru(2)(hedp)(2)X]x16H(2)O [X = Cl (1), Br (2)], K(3)[Ru(2)(hedp)(2)(H(2)O)(2)]x6H(2)O (3), and Na(7)[Ru(2)(hedp)(2)Fe(CN)(6)]x24H(2)O (4), where hedp represents 1-hydroxyethylidenediphosphonate [CH(3)C(OH)(PO(3))(2)](4-), were synthesized and structurally characterized. Compounds 1, 2, and 4 show linear chain structures in which the mixed-valent [Ru(2)(hedp)(2)](3-) dimers are linked by X(-) or [Fe(CN)(6)](4-) bridges. Compound 3 contains discrete species of [Ru(2)(hedp)(2)(H(2)O)(2)](3-) where the axial positions of [Ru(2)(hedp)(2)](3-) paddlewheel are terminated by water molecules. Magnetic studies show that significant antiferromagnetic exchanges are mediated between the [Ru(2)(hedp)(2)](3-) (S = 3/2) units through halide bridges in compounds 1 and 2.     

Lanthanide diruthenium(II,III) compounds showing layered and PtS-type open framework structures

Two types of lanthanide diruthenium phosphonate compounds, based on the mixed-valent metal-metal bonded paddlewheel core of Ru(2)(hedp)(2)(3-) [hedp = 1-hydroxyethylidenediphosphonate, CH(3)C(OH)(PO(3))(2)], have been prepared with the formulas Ln(H(2)O)4[Ru(2)(hedp)(2)(H(2)O)2].5.5H(2)O (1.Ln, Ln = La, Ce) and Ln(H(2)O)4[Ru(2)(hedp)(2)(H(2)O)(2)].8H(2)O (2.Ln, Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er). In both types, each Ru(2)(hedp)2(H2O)23- unit is linked by four Ln(3+)ions through four phosphonate oxygen (OP) atoms and vice versa. The geometries of the {LnO(P4)} group, however, are different in the two cases. In 1.Ln, the geometry of {LnO(P4)} is closer to a distorted plane, and thus a square-grid layer structure is found. In 2.Ln, the geometry of {LnO(P4)} is better described as a distorted tetrahedron; hence, a unique PtS-type open-framework structure is observed. The channels generated in structures 2.Ln are filled with water aggregates with extensive hydrogen-bond interactions. The magnetic and electrochemical properties are also investigated.     

Heterometallic cubanes: syntheses, structures, and magnetic properties of lanthanide(III)-nickel(II) architectures

Reactions of lanthanide(III) perchlorate (Ln = Dy, Tb, and Gd), nickel(II) acetate, and ditopic ligand 2-(benzothiazol-2-ylhydrazonomethyl)-6-methoxyphenol (H(2)L) in a mixture of methanol and acetone in the presence of NaOH resulted in the successful assembly of novel Ln(2)Ni(2) heterometallic clusters representing a new heterometallic 3d-4f motif. Single-crystal X-ray diffraction reveals that all compounds are isostructural, with the central core composed of distorted [Ln(2)Ni(2)O(4)] cubanes of the general formula [Ln(2)Ni(2)(μ(3)-OH)(2)(OH)(OAc)(4)(HL)(2)(MeOH)(3)](ClO(4))·3MeOH [Ln = Dy (1), Tb (2), and Gd (3)]. The magnetic properties of all compounds have been investigated. Magnetic analysis on compound 3 indicates ferromagnetic Gd···Ni exchange interactions competing with antiferromagnetic Ni···Ni interactions. Compound 1 displays slow relaxation of magnetization, which is largely attributed to the presence of the anisotropic Dy(III) ions, and thus represents a new discrete [Dy(2)Ni(2)] heterometallic cubane exhibiting probable single-molecule magnetic behavior.     

Copper(II) and iron(III) complexes of N-nitroso-N- alkylhydroxylamines,and the X-ray crystal structures of bis(N-nitroso-N-isopropylhydroxylaminato)copper(II) and tris(N-nitroso-N-propylhydroxylaminato)iron(III)

N-nitroso-N-alkylhydroxylamines have been prepared by hydrolysis of the mixture obtained by reaction of nitric oxide with Grignard reagents, and stabilized as their copper(II) or iron(III) complexes, Cu(RN₂O₂)₂ and Fe(RN₂O₂)₃, where R is, for example, Me, Et, Prⁱ, Bu^iso, Ph, n-C₈H₁₇ or n-C₁₂H₂₅. The complexes have been characterized by analytical, magnetic and spectroscopic measurements. By single-crystal X-ray methods Cu(PrⁱN₂O₂)₂ has been found to be trans-planar and Fe(PrⁿN₂O₂)₃ has a facial octahedral structure; in each complex the NO bond lengths are equal with no significant variation between the copper and iron complexes.     

Strontium selenogermanate(III) and barium selenogermanate(II,IV): synthesis, crystal structures, and chemical bonding

The new selenogermanates Sr2Ge2Se5 and Ba2Ge2Se5 were synthesized by heating stoichiometric mixtures of binary selenides and the corresponding elements to 750 degrees C. The crystal structures were determined by single-crystal X-ray methods. Both compounds adopt previously unknown structure types. Sr2Ge2Se5 (P2(1)/n, a = 8.445(2) A, b = 12.302 A, c = 9.179 A, beta = 93.75(3) degrees, Z = 4) contains [Ge4Se10]8- ions with homonuclear Ge-Ge bonds (dGe-Ge = 2.432 A), which may be described as two ethane-like Se3Ge-GeSeSe2/2 fragments sharing two selenium atoms. Ba2Ge2Se5 (Pnma, a = 12.594(3) A, b = 9.174(2) A, c = 9.160(2) A, Z = 4) contains [Ge2Se5]4- anions built up by two edge-sharing GeSe4 tetrahedra, in which one terminal Se atom is replaced by a lone pair from the divalent germanium atom. The alkaline earth cations are arranged between the complex anions, each coordinated by eight or nine selenium atoms. Ba2Ge2Se5 is a mixed-valence compound with GeII and GeIV coexisting within the same anion. Sr2Ge2Se5 contains exclusively GeIII. These compounds possess electronic formulations that correspond to (Sr2+)2(Ge3+)2(Se2-)5 and (Ba2+)2- Ge2+Ge4+(Se2-)5. Calculations of the electron localization function (ELF) reveal clearly both the lone pair on GeII in Ba2Ge2Se5 and the covalent Ge-Ge bond in Sr2Ge2Se5. Analysis of the ELF topologies shows that the GeIII-Se and GeIV-Se covalent bonds are almost identical, whereas the GeII-Se interactions are weaker and more ionic in character.     

Manganese(III,IV) and manganese(III) oxide clusters trapped by copper(II) complexes

Reactions of quinquedentate Schiff base ligands with Mn and Cu ions afforded icosa- and hexadecanuclear mixed-metal clusters in which dinuclear CuII complexes trapped oxo-bridged [MnIII8MnIV4O12] and [MnIII6O6] cores, respectively. Maximum entropy method analysis for synchrotron X-ray diffraction data was used to determine the oxidation states of the Mn ions.     

Compositions and structures of copper hexacyanoferrates(II) and (III): experimental results

The preparation, composition and structure of copper hexacyanoferrates have been investigated. Three methods were used: precipitation, local growth in an aqueous solution, and growth in a gel. Four compounds were obtained, either in powdered form or as single crystals: Cu(II)(2)Fe(II)(CN)(6) . xH(2)O, Cu(II)(3)[Fe(III)(CN)(6)](2) . xH(2)O, Na(2)Cu(II)Fe(II)(CN)(6) . 10H(2)O and K(2)Cu(II)Fe(II)(CN)(6). Powders of Cu(II)(2)Fe(II)(CN)(6) . xH(2)O and Cu(II)(3)[Fe(III) (CN)(6)](2) . xH(2)O are easily prepared by precipitation and can also be obtained by local growth. They crystallise generally with cubic symmetry, in space group Fm3m, and are structurally disordered. The mixed copper hexacyanoferrates of general formulae M(1)(2)Cu(II)Fe(II)(CN)(6) or M(I)Cu(II)Fe(III)(CN)(6) (here M(I) is Na, K) were not obtained by precipitation. The appropriate method was local growth for the preparation of powders of K(2)Cu(II)Fe(II)(CN)(6). Single crystals of Na(2)Cu(II)Fe(II)(CN)(6) were obtained by growth in a gel, and their study using single crystal X-ray diffraction revealed a new monoclinic structure.     

Crystal structures and magnetic interactions in nickel(II) dibridged complexes formed by both phenolate oxygen-azide,or methanlate groups

Abstract  

Tridentate Schiff base ligands L¹ and L², derived from the condensation of 2-hydroxy-3-methoxybenzaldehyde (L) with 2-aminoethanol or 2-aminobutan-1-ol, react with nickel chloride, azide, or thiocyanate to give rise to two dinuclear complexes of formulas [Ni₂(L)(L¹)₂N₃]·H₂O (1), [Ni₂(L²)₃(μ_1,1-N₃)]·2H₂O (2), and one tretranuclear complex [Ni₂(L²)₂(NCS)]₂(C₂H₅OH)₂ (3), where L¹ = HOCH₂CH(C₂H₅)NCHC₆H₃(O⁻)(OCH₃) and L² = HO(CH₂)₂NCHC₆H₃(O⁻)(OCH₃). We have characterized these complexes by analytical, crystal structures, and variable temperature magnetic susceptibility measurements. The magnetic properties of the complexes are studied by magnetic susceptibility (χ_M) vs. temperature measurements. The χ_M T vs. T plots reveal that compounds 1, 2 and 3 are ferromagnetically coupled.     

Syntheses, crystal structures and properties of new lead(II) or bismuth(III) selenites and tellurite

Four new lead(II) or bismuth(III) selenites and a tellurite, namely, Pb(3)(TeO(3))Cl(4), Pb(3)(SeO(3))(2)Br(2), Pb(2)Cd(3)(SeO(3))(4)I(2)(H(2)O), Pb(2)Ge(SeO(3))(4) and BiFe(SeO(3))(3), have been prepared and structurally characterized by single crystal X-ray diffraction (XRD) analyses. These compounds exhibit five different types of structures. The structure of Pb(3)(TeO(3))Cl(4) features a three-dimensional (3D) lead(II) chloride network with tellurite anions filling in the 1D tunnels of Pb(4) 4-member rings (MRs) along the c-axis. Pb(3)(SeO(3))(2)Br(2) contains a 3D network composed of lead(II) selenite layers interconnected by bromide anions. Pb(2)Cd(3)(SeO(3))(4)I(2)(H(2)O) is a 3D structure based on 2D cadmium(II) selenite layers which are further connected by 1D lead(II) iodide ladder chains with lattice water molecules located at the 1D tunnels of the structure. Pb(2)Ge(SeO(3))(4) features a 3D framework constructed by the alternate arrangement of lead(II) selenite layers and germanium(iv) selenite layers in the [100] direction. The structure of BiFe(SeO(3))(3) is built on the 3D anionic framework of ion(III) selenite with the bismuth(III) ions located at its Fe(6)Se(6) 12-MR tunnels. Pb(3)(TeO(3))Cl(4) (Pna2(1)) is polar and BiFe(SeO(3))(3) (P2(1)2(1)2(1)) is noncentrosymmetric. Powder second-harmonic generation (SHG) measurements using 1064 nm radiation indicate that BiFe(SeO(3))(3) exhibits a weak SHG efficiency of about 0.2 × KH(2)PO(4) (KDP). Magnetic property measurements for BiFe(SeO(3))(3) show a dominant antiferromagnetic interaction with weak spin-canting at low temperatures. IR, UV-vis and thermogravimetric, as well as electronic structure calculations were also performed.     

Two solvent and temperature dependent copper(II) compounds formed by a flexible ligand: syntheses, structures and SC-SC transformation

A nonporous neutral framework [CuCl(2)(m-bttmb)(2)](n) (1) was changed into a porous ionic {[Cu(m-bttmb)(2)(H(2)O)Cl]Cl(CH(3)CN)(0.5)(H(2)O)(2.75)}(n) (2) by simply increasing the amount of CH(3)CN in the mixed solvent (CH(3)CN and H(2)O) or temperature in the reactions of CuCl(2)·2H(2)O with 1,3-bis(triazol-1-ylmethyl)-2,4,6-trimethylbenzene (m-bttmb). 1 undergoes transformation into 2 when treated with CH(3)CN. Both 1 and 2 have 2D 4-connected (4,4) network architectures but in different packing arrangements. These compounds have been characterized by single-crystal X-ray diffraction analysis, elemental analysis, IR spectra and thermogravimetric analysis. This work may provide a way to control the formation of neutral or ionic frameworks, as well as porosities by adjusting the polarity and components of the solvents.