Synthesis and crystal structure of a cyanide-bridged one-dimensional nickel(II) complex with alternating [Ni(En)<Superscript>2</Superscript>]<Superscript>2+</Superscript> and [Ni(CN)<Subscript>4</Subscript>]<Superscript>2−</Superscript> ions

The complex [Ni(En)₂][Ni(CN)₄] · 3.5H₂O (I) (En = ethylenediamine) was synthesized by the reaction of [Ni(En)₂](ClO₄)₂ and K₂[Ni(CN)₄] in an H-shaped tube. The crystal structure of I has been determined by single-crystal X-ray analysis. The crystal of complex I is orthorhombic, space group Pnna with a = 28.151(3), b = 8.3946(8), c = 14.5441(13)Å, M =404.76, Z = 8, V = 3437.0(5)ų. The structure of complex I reveals infinite zigzag chains shaped structure are formed by cis-Ni(En)₂-μ-(NC)₂, cis-μ-(NC)₂Ni(CN)₂, and trans-μ-(CN)₂Ni(En)₂.     

Structures of the complex ions [CuCl<Subscript>4</Subscript>]<Superscript>2−</Superscript> and [CuCl<Subscript>5</Subscript>]<Superscript>3−</Superscript>

The electronic structures of the complex ions [CuCl₄]^2? and [CuCl₅]^3? were analyzed in terms of the extended angular overlap model (AOM) with consideration to sd and pd mixing. The total antibonding orbital energies of these ions show no anomalies in the transition from a tetrahedron to a planar square [CuCl₄]^2? and from a trigonal bipyramid to a tetragonal pyramid [CuCl₅]^3?. Presumably, the existence of numerous intermediate forms of these complexes is mainly due to the packing effects rather than the electronic factors.     

Stabilization of [Sc(NCS)<Subscript>6</Subscript>]<Superscript>3−</Superscript> anion by [M(18C6)]<Superscript>+</Superscript> complexes in solvation systems

The [M(18C6)]₄[Sc(NCS)₆]Cl · nH₂O complexes were established to form in the solutions ScCl _x -Solv-MNCS-18C6, where Solv is ethanol, THF, acetonitrile, or isopropyl alcohol; M = Na, K; 18C6 is 1,4,7,10,13,16-hexaoxocyclooctadecane. X-ray diffraction analysis of [K(18K6)]₄[Sc(NCS)₆]Cl · 3.33H₂O showed that the thiocyanate ion was coordinated by Sc through the N atom. The structure consists of octahedral Sc(NCS) ₆ ^3? that are united via nonvalent K-S interaction with macrocyclic dimers [M(18C6)]₂ into chains. Each 18C6 molecule coordinates one K atom.     

Synthesis and structure of cobalt(III) dimethylglyoximate with [FeF<Subscript>5</Subscript>(H<Subscript>2</Subscript>O)]<Superscript>2−</Superscript> anion

A new complex [Co(DH)₂(Thio)₂]₂[FeF₅(H₂O)] · 2CH₃OH (where DH^? is dimethylglyoxime monoanion, Thio is thiourea molecule) was synthesized and its structure was determined. The coordination polyhedron of the Co(III) atoms in two centrosymmetric complex cations is an octahedron, formed by four N atoms of two dimethylglyoxime residues and two S atoms of coordinated Thio molecules. One of the Thio molecules is almost perpendicular to a metal cycle (the dihedral angle 87.8(1)°), which is responsible for realization of intermolecular hydrogen bond N-H···O (N···O 2.990(3) Å). The second Thio molecule is almost parallel to the equatorial CoN₄ fragment (the dihedral angle 159.4(1)°) to give rise to intramolecular π-π interaction between practically planar Thio molecule and one of the π-delocalized metal cycle. The Fe(III) coordination polyhedron is an octahedron, formed by five F atoms and by the O atom of coordinated water molecule. The key role in the crystal structure organization is played by intermolecular hydrogen bonds N-H···F, N-H···O, N-H···S, the intramolecular bonds O-H···O, formed by the donor NH₂ groups of a complex cation with the F atoms of the [FeF₅(H₂O)]^2? and the donor-acceptor groups of the Thio fragments.     

Kinetic studies on acid-catalysed aquation of some [Cr(ox)<Subscript>2</Subscript>(amino acid)]<Superscript>2−</Superscript> complexes

Three chromium(III) complexes of general formula [Cr(ox)₂(Aa)]²⁻ (Aa is an α-amino acid, namely alanine, valine or cysteine) were obtained and characterized in solution. In acidic solutions, [Cr(ox)₂(Aa)]²⁻ undergo acid-catalysed aquation to cis-[Cr(ox)₂(H₂O)₂]⁻ and the appropriate amino acid. The process goes through a metastable intermediate with monodentate amino acid coordinated via the carboxylate oxygen atom. The kinetics of the chelate ring opening were studied under isolation conditions. The determined pseudo-first-order rate constants were linearly dependent on [H⁺]. A mechanism is proposed, in which the reactive form of substrate is in the form of the conjugate acid.     

Structure of sulfanilamide-containing cobalt(III) dioximates with the [ZrF<Subscript>6</Subscript>]<Superscript>2−</Superscript> and [BF<Subscript>4</Subscript>]<Superscript>−</Superscript> anions

The complexes [Co(DH)₂(Sam)₂]₂[ZrF₆]·5H₂O (I) and [Co(DH)₂(Sam)₂][BF₄]·H₂O (II), where DH^? is the dimethylglyoxime monoanion, and Sam is para-aminobenzenesulfamide (sulfanilamide, white streptocid), were synthesized, and their crystal structures were determined by X-ray diffraction analysis. The coordination polyhedron of the Co³⁺ atom is an N₆ octahedron formed by four nitrogen atoms of the two dimethylglyoxime residues and two nitrogen atoms of the Sam fragments. The latter are realized in virtually parallel orientation relative to the polyhedron of the metal atom and its equatorial plane; the average value of the dihedral angles is 26.8(1)°, and there is π-π interaction between the benzene rings of the Sam fragments and the π delocalized equatorial metallocycle. The deviation of the cobalt atom from the four-angle plane is up to 0.009(1) Å. The (Co-N)_DH? and (Co-N)_Sam distances in the [Co(DH)₂(Sam)₂]⁺ complex cations vary from 1.892(2) Å to 1.907(3) Å and from 2.000(2) Å to 2.012(2) Å, respectively. The [ZrF₆]^2? and [BF₄]^? complex anions play the major role in crystal formation; they produce a substantial effect on the formation of a complex system of hydrogen bonds.     

<Superscript>13</Superscript>C-labeled bilirubin: synthesis of 3<Superscript>1</Superscript>(3<Superscript>2</Superscript>),17<Superscript>1</Superscript>(17<Superscript>2</Superscript>)-di-[<Superscript>13</Superscript>C]-mesobilirubin-XIIIα

Abstract  The title compound, labeled with ¹³C in the ethyl groups was synthesized from K¹³CN and low-molecular-weight components. The synthetic relay compound was 3¹(3²)[¹³C]-xanthobilirubinic acid methyl ester in a synthetic route that leads to a label in the ethyl β-substituent of a dipyrrinone model for bilirubin. This labeled dipyrrinone was oxidatively coupled to the dimethyl ester of mesobiliverdin-XIIIα, thereby providing a route to a ¹³C-labeled mesobiliverdin and mesobilirubin, with one carbon of each ethyl being 98% ¹³C-enriched. Graphical Abstract        

Synthesis and structure of cobalt(III) α-dimethylglyoximates containing thiourea and [ZrF<Subscript>6</Subscript>]<Superscript>2−</Superscript> anion

Two novel coordination compounds of thiourea-containing trans-octahedral trans-dioximates of trivalent cobalt [Co(DH)₂(Tu)₂]₂[ZrF₆]·H₂O and [Co(NioxH)₂(Tu)₂]₂[ZrF₆]·3H²O, where DH^? is the monoanion of dimethylglyoxime, NioxH^? is the monoanion of 1,2-cyclohexanone dioxime, Tu is thiourea, are prepared and characterized by single crystal X-ray diffraction. The structures manifest pairwise an almost parallel and perpendicular arrangement of the Tu fragment in respect to the equatorial plane of the coordination core, accompanied by a development of non-bonding intramolecular π-π-and N-H...O-interactions affecting the structures of the compounds in question. The formation of the crystal structures is primarily governed by outer-sphere [ZrF₆]^2? anions and crystallization water molecules.     

Structural investigation of salts containing ions [Pd(NH<Subscript>3</Subscript>)<Subscript>4</Subscript>]<Superscript>2+</Superscript> and [IrF<Subscript>6</Subscript>]<Superscript>2–</Superscript>

Double complex salts (DCS) α-[Pd(NH₃)₄][IrF₆]·H₂O (P2₁/m, a = 6.3181(3) Å, b = 10.8718(5) Å, с = 7.4526(4) Å, β = 103.568(2)°), β-[Pd(NH₃)₄][IrF₆]·H₂O (P2₁/с, a = 8.5773(3) Å, b = 10.8791(4) Å, с = = 12.6741(3) Å, β = 122.497(2)°), [Pd(NH₃)₄]₃[IrF₆]₂Cl₂·H₂O (P-1, a = 7.6080(2) Å, b = 7.6274(2) Å, с = 11.8070(3) Å, β = 122.497(2)°), and [Pd(NH₃)₄]₂[IrF₆]NO₃ (Fm-3m, a = 11.21210(10) Å) have been synthesized and structurally characterized for the first time. The existence of polymorphs for the DCS has been revealed. The influence of the chemical composition of the initial reagents on the reaction course and, respectively, the products, has been demonstrated. A hypothesis on the influence of the second coordination sphere on the formation of one or the other polymorph of the DCS has been suggested. It has been shown that the series α-[Pd(NH₃)₄][МF₆]·H₂O (M = Pt, Pd) exhibits isostructurality.     

Synthesis and thermolysis of lithium aluminum double hydroxide containing [Fe(OH)Edta]<Superscript>2−</Superscript>

The reaction of the chloride form of lithium aluminum layered double hydroxide (Li-Al LDH) with an aqueous solution of NaFeEdta · 2H₂O (pH 3.7) was studied. Anion exchange of chloride ions for [FeEdta]^? anions almost does not occur under the conditions of our experiment. Increasing pH to 8.0 initiates anion exchange of chloride ions for [Fe(OH)Edta]^2? anions, generating Li-Al LDH, whose structure is built of metal-hydroxide layers [LiAl₂(OH)₆]⁺ and layers containing [Fe(OH)Edta]^2? anions and water molecules. Thermolysis of Li-Al-[Fe(OH)Edta] was studied in an inert atmosphere and in vacuo. Heating to 220°C mainly eliminates interlayer water molecules. A further rise in temperature induces the dehydration of metal-hydroxide layers and OH groups of [Fe(OH)Edta]^2? anions and the destruction of the organic component of the anionic complex. At 375°C, an X-ray amorphous product is formed, in which most iron is in the form of Fe²⁺ cations. With increasing thermolysis temperature to 450°C, a magnetically ordered solid phase containing Fe²⁺ cations appears. Further temperature elevation to 550°C generates an α-Fe phase.     

Study on the thermal behavior of the complexes of the type [PdX<Subscript>2</Subscript>(tdmPz)] (X = Cl<Superscript>−</Superscript>, Br<Superscript>−</Superscript>, I<Superscript>−</Superscript>, SCN<Superscript>−</Superscript>)

Four new mononuclear Pd(II) complexes of the type [PdX₂(tdmPz)] {X = Cl⁻ (1); Br⁻ (2); I⁻ (3); SCN⁻ (4); tdmPz = 1-thiocarbamoyl-3,5-dimethylpyrazole} have been synthesized and characterized by elemental analysis, IR spectroscopy, ¹H and ¹³C{¹H}-NMR experiments. The thermal behavior of the complexes 1–4 has been investigated by means of thermogravimetry (TG) and differential thermal analysis (DTA). From the initial decomposition temperatures, the thermal stability of the complexes can be ordered in the sequence: 3 < 4 ≡ 2 < 1. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

Syntheses and structures of six-coordinate K[Ga<Superscript>III</Superscript>(Cydta)] · 2H<Subscript>2</Subscript>O and K[Ga<Superscript>III</Superscript>(Pdta)] · 3H<Subscript>2</Subscript>O complexes

The title complexes, K[Ga^III(Cydta)] · 2H₂O(Cydta = trans-1,2-cyclohexanediaminetetraacetic acid) and K[Ga^III(Pdta)] · 3H₂O (Pdta = propylenediaminetetraacetic acid), were prepared, and their structures were studied by IR spectra, elemental analyses, NMR spectra, and single-crystal X-ray diffraction techniques. In the K[Ga^III(Cydta)] · 2H₂O complex, the Ga³⁺ is six-coordinated by the Cydta ligand yielding an octahedral conformation, and the complex crystallizes in the monoclinic system with the P2₁/c space group. The crystal data are as follows: a = 16.5039(19), b = 13.1499(16), c = 8.5204(10) Å, β = 101.650(2)°, V = 1811.0(4) ų, Z = 4, ρ = 1.757 g/cm³, μ = 1.805 mm^?1, F(000) = 984, R = 0.0291, and wR = 0.0698 for 3713 observed reflections with I ≥ 2σ(I). In the K[Ga^III(Pdta)] · 3H₂O complex, the Ga³⁺ is also six-coordinated by the Pdta ligand yielding an almost standard octahedral conformation, and the complex crystallizes in the orthorhombic system with P2₁2₁2₁ space group. The crystal data are as follows: a = 8.8913(10), b = 11.6181(13), c = 17.0227(19) Å, V = 1758.4(3) ų, Z = 4, ρ = 1.757 g/cm³, μ = 1.862 mm^?1, F(000) = 952, R = 0.0288, and wR = 0.0724 for 3556 observed reflections with I ≥ 2σ(I).     

Peroxide derivatives of heteropoly compounds with Keggin anions [PW<Subscript>12</Subscript>O<Subscript>40</Subscript>]<Superscript>3−</Superscript> and [SiW<Subscript>12</Subscript>O<Subscript>40</Subscript>]<Superscript>4−</Superscript>: Synthesis and structure

Peroxide derivatives of heteropoly compounds with Keggin anions [PW₁₂O₄₀]^3? and [SiW₁₂O₄₀]^4? are isolated in an individual state from concentrated hydrogen peroxide solutions and characterized by physicochemical methods. The structure of Ba₂[SiW₁₂O₄₀] · 4H₂O₂ · 11H₂O (I) is solved by X-ray crystallography. Crystals of compound I (H₃₀Ba₂O₅₉Si₁W₁₂, FW = 3483.21) are monoclinic, space group C2/c, a = 24.981(2) Å, b = 12.2103(11) Å, c = 18.7142(17) Å, β = 122.620(2)^o, V = 4808.0(8) ų, Z = 4. The structure contains Keggin anions [SiW₁₂O₄₀]^4?; all hydrogen peroxide molecules are coordinated to Ba²⁺ cations.     

Structure and stability of endohedral complexes <Superscript>4/2</Superscript>X@(HAlNH)<Subscript>2</Subscript> (X = N,P, As,C<Superscript>−</Superscript>, Si<Superscript>−</Superscript>)

The structures of a closo-hedral cluster (HAlNH)₁₂ and endohedral complexes ^4/2X@(HAlNH)₁₂ (X = N, P, As, C⁻, Si⁻) are studied by density functional theory (DFT) at the B3LYP/6-31G(d) level. The geometries, natural bond orbital (NBO), vibrational frequency (ν₁), energetic parameters, magnetic shielding constants (σ), and nucleus independent chemical shifts (NICSs) are discussed. It is found that all guest species are minima at the cage center. Inclusion energies (ΔE _inc) of all species are negative except those of ⁴N and ^4/2P. In all species, the endohedral quartet states (⁴X) are energetically less favorable than their doublet states (²X). The calculations predict that caged X states only donate <0.50 e to the cage and preserve their unencapsulated ground states.     

Photochemistry of PtBr<Subscript>6</Subscript><Superscript>2−</Superscript> in aqueous solution

Photochemistry of the PtBr₆ ²⁻ complex in aqueous solution was studied by steady-state and laser flash photolysis (308 nm). The multistep photoaquation of the complex occurs in the nano-and microsecond time intervals without the formation of intermediate platinum(III) complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2277–2283, December, 2007.     

Synthesis of the [<Superscript>2</Superscript>H,<Superscript>15</Superscript>N]-labeled antiviral drug “triazavirine”

Selective methods for the incorporation of stable isotopes ¹⁵N and ²H into the structure of antiviral medicine “triazavirine” 1 were developed. The synthesized isotopically modified “triazavirine” 1– ² H ₃ , ¹⁵ N ₃ contained the labeled atoms in both the azole and the azine rings. ¹³C and ¹⁵N NMR spectra of the isotope-containing sample 1– ² H ₃ , ¹⁵ N ₃ were thoroughly analyzed.     

Kinetic and thermodynamic studies on reactions of [PtCl(bpma)]<Superscript>+</Superscript> and [Pt(bpma)H<Subscript>2</Subscript>O]<Superscript>2+</Superscript> (bpma = <Emphasis Type="Italic">bis</Emphasis>-(2-pyridylmethyl)amine) with some azoles and diazines

Substitution reactions of the complexes [Pt(bpma)H₂O]²⁺ and [PtCl(bpma)]⁺, where bpma is bis-(2-pyridylmethyl)amine, with the nitrogen-donor ligands 1,2,4-triazole, pyrazole and pyridazine were studied in aqueous 0.1 M NaClO₄ using variable-temperature UV–VIS spectrophotometry. The reactions of the aqua complex were studied at pH 2.5, and those of the chloro complex were studied in the presence of 10 mM NaCl to prevent their hydrolysis. The values obtained for the second-order rate constants indicate that the complexes with bpma are more reactive than those with diethylenetriamine. In both cases, the aqua complexes are more reactive than the corresponding chloro complexes. The reactivity of the incoming ligands follows the order: 1,2,4-triazole > pyridazine > pyrazole. Activation parameters were determined for all the reactions, and the negative entropies of activation (∆S^≠) support an A or Ia mechanism.     

Research on photosensitivity of benzoquinones and benzoquinoneimines in the sunlight/Fe<Superscript>2+</Superscript>/S<Subscript>2</Subscript>O<Subscript>8</Subscript><Superscript>2−</Superscript> system

This paper investigated the photodegradation characteristics of benzoquinones and benzoquinoneimines. The photosensitivity of benzoquinones and benzoquinoneimines were analyzed by measuring the yield of SO ₄ ^?· in a light/Fe²⁺/S₂O₈ ^2? system and the degradation mechanism of benzoquinones, then discussed benzoquinoneimines in light/Fe²⁺/S₂O₈ ^2? and light/S₂O₈ ^2? system. The results revealed that a more aggressive oxidation of benzoquinones and benzoquinoneimines by the sunlight/Fe²⁺/S₂O₈ ^2? method showed a more rapid and more complete removal of chromaticity than that of the UV/Fe²⁺/S₂O₈ ^2? method. It was showed that they were photosensitizers, and they could generate ¹O₂ and O ₂ ^?· which could promote the formation of SO ₄ ^?· and ^·OH in the sunlight system. Nevertheless, for benzoquinones, the sunlight/S₂O₈ ^2? method was superior to the UV/S₂O₈ ^2? method. For benzoquinoneimines, the sunlight/S₂O₈ ^2? method was inferior to the UV/S₂O₈ ^2? method. In addition, the yield of SO ₄ ^?· in the sunlight/Fe²⁺/S₂O₈ ^2? system was more than that of the UV/Fe²⁺/S₂O₈ ^2? system. Therefore, the photosensitivity of benzoquinones is superior to benzoquinoneimines in water treatment.     

A study of the hydrolysis of ZrF<Stack><Subscript>6</Subscript><Superscript>2−</Superscript></Stack> and the structure of intermediate hydrolysis products by <Superscript>19</Superscript>F and <Superscript>91</Superscript>Zr NMR in the 9.4 T field

The high-field ¹⁹F and ⁹¹Zr NMR method is used to study the hydrolysis and polycondensation of hexafluorozirconate ZrF₆²⁻ in aqueous and water-peroxide solutions. During hydrolysis in aqueous solutions only ZrF₆²⁻ and F⁻ ions were observed by NMR, however, in the water-peroxide medium, an intermediate product of hydrolysis ([F₅Zr-OO-ZrF₅]⁴⁻ dimer) was detected. The dimer structure is confirmed by ¹⁹F and ⁹¹Zr NMR. In high fields (¹⁹F NMR frequency > 200 MHz), the fluorine exchange between ZrF₆²⁻ and F⁻ is slow in the ¹⁹F NMR scale and has a multisite character.     

Magnetic study of a cyano-bridged bimetallic complex with Cu<Superscript>2+</Superscript> macrocycle and [Fe(CN)<Subscript>6</Subscript>]<Superscript>3−</Superscript> ions as building blocks

A new bimetallic cyano-bridged complex, based on copper(II) macrocycle and hexacyanoiron(III) as building blocks, [CuL(H₂O)₂]{[CuL][Fe(CN)₆] · 2H₂O} (1) (L = 1,3,6,8,11,14-hexaazatricyclo[12.2.1.18,11]-octadecane) has been synthesized and magnetically characterized. Make a study of magnetic using a chain model which takes into account of monomeric impurity confirm showing an antiferromagnetic coupling in paramagnetic ions with J = −0.170 cm⁻¹ and 3.56 % impurity.