Effect of free valence on the characteristics of internal rotation in <Emphasis Type="Italic">n</Emphasis>-alkyl radicals

A study of internal rotation in the radicals n-C _n H_2n+1C^·H₂, (2 ≤ n ≤ 7) was carried out for the case of rotation around the bonds not including the radical center. 21 potential functions of internal rotation V(φ) were calculated. The coefficients in V(φ) were shown to depend only on the immediate environment at the bond of rotation. Characteristics of internal rotation in n-alkyl radicals were compared with related parameters of the corresponding alkane molecules. The generalized function V _av(φ) with the coefficients defined only by the position of the bond of rotation in the hydrocarbon chain and possessing the transposition property were proposed. The functions V _av(φ) were recommended for the simulation of the structure and properties of large molecules containing hydrocarbon fragments. This work continues a systematic study on the characteristics of the internal rotation in the n-alkane molecules and the groups containing free valence in n-alkyl radicals.     

Apparent Molar Volumes of Symetric and Asymetric Tetraalkylammonium Salts in Dilute Aqueous Solutions

The apparent molar volumes, V_φ of tetramethylammonium, tetraethylammonium, tetrabutylammonium, butyltriethylammonium, dibutyldiethylammonium, and tributylethylammonium bromides have been measured at 298.15K in the concentration range from 0.01 to 0.04mol⋅kg⁻¹. The concentration dependence of V_φ is given using the Redlich and Meyer relation. The apparent molar volume at infinite dilution, V∘_φ, and the empirical constant, B_V, have been calculated. The CH₂-group contribution has been obtained by the additivity rule. The results were interpreted in terms of solute–solvent interactions.     

Formation and structure of diruthenium complexes Ru2(CO)6−n (PPh3) n {μ-C(CH=CHPh)C(Ph)C(CH=CHPh)C(Ph)} (n=1, 2)

Ruthenium carbonyl triphenylphosphine complexes Ru₂(CO)_6−n (PPh₃) _n {μ-C(CH=CHPh)C(Ph)C(CH=CHPh)C(Ph)} (n=1, 2) were obtained by the reaction of complex Ru₂(CO)₆{μ-C(CH=CHPh)C(Ph)C(CH=CHPh)C(Ph)} containing the ruthenacyclopentadiene moiety with PPh₃ in refluxing toluene. The complexes were characterized by IR and by¹H,¹³C, and³¹P NMR spectroscopy, and by X-ray analysis. The monophosphine derivative is identical to the complex formed by fragmentation of the Ru₃(CO)₈(PPh₃){μ-C(CH=CHPh)C(Ph)C(CH=CHPh)C(Ph)} cluster and contains the PPh₃ ligand at the ruthenium atom of the ruthenacyclopentadiene moiety. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1836–1843, September, 1998     

Volumetric Properties of Some Aliphatic Mono- and Dicarboxylic Acids in Water at 298.15 K

The apparent molar volumes, V _φ , of two series of homologous aliphatic carboxylic acids, H(CH₂) _n COOH [n=0–5] and (CH₂) _n (COOH)₂ [n=0–5], were determined in dilute aqueous solutions by density measurements at T=298.15 K. Densities were measured using a vibrating-tube densimeter (DMA 5000, Anton Paar, Austria) at T=298.15 K. These results were used to calculate the apparent molar volumes of each solute over the concentration range 0.0050≤m/(mol⋅kg⁻¹)≤0.3000. Values of the apparent molar volumes of undissociated acids V_f(u)⁰V_{\phi (u)}^{0} were also calculated. The variation of V_f(u)⁰V_{\phi (u)}^{0} was determined as a function of the aliphatic chain length of the studied carboxylic acids.     

Oxo Peroxo Glycolato Complexesof Vanadium (V). Crystal Structureof (NBu4)2[V2O2(O2)2(C2H2O3)2]ċH2O

Summary.  Oxo peroxo glycolato complexes of vanadium(V) (M ₂[V₂O₂(O₂)₂(C₂H₂O₃)₂]ċnH₂O (n=0, 1; M=NBu₄ ⁺ (1), K⁺ (2), NH₄ ⁺ (3), Cs⁺ (4), NPr₄ ⁺ (5)) as well as (NBu₄)₂[V₂O₄(C₂H₂O₃)₂]ċ H₂O (6) have been prepared and characterized by spectroscopic methods. X-Ray structure analysis of 1 revealed the presence of dinuclear [V₂O₂(O₂)₂(C₂H₂O₃)₂]²⁻ anions with a (chemical structure) bridging core and six coordinated vanadium(V) atoms in a distorted pentagonal pyramidal array. Received July 12, 1999. Accepted (revised) October 28, 1999     

Divalent transition metal complexes of 3,5-pyrazoledicarboxylate

New divalent transition metal 3,5-pyrazoledicarboxylate hydrates of empirical formula Mpz(COO)₂(H₂O)₂, where M=Mn, Co, Ni, Cu, Zn and Cd (pz(COO)₂=3,5-pyrazoledicarboxylate), metal hydrazine complexes of the type Mpz(COO)₂N₂H₄ where M=Co, Zn or Cd and Mpz(COO)₂nN₂H₄·H₂O, where n=1 for M=Ni and n=0.5 for M=Cu have been prepared and characterized by physico-chemical methods. Electronic spectroscopic data suggest that Co and Ni complexes adopt an octahedral geometry. The IR spectra confirm the presence of unidentate carboxylate anion (Δν=ν_asy(COO^–)–ν_sym(COO^–)>215 cm^–1) in all the complexes and bidentate bridging hydrazine (ν_N–N=985–950 cm^–1) in the metal hydrazine complexes. Both metal carboxylate and metal hydrazine carboxylate complexes undergo endothermic dehydration and/or dehydrazination followed by exothermic decomposition of organic moiety to give the respective metal oxides as the end products except manganese pyrazoledicarboxylate hydrate, which leaves manganese carbonate. X-ray powder diffraction patterns reveal that the metal carboxylate hydrates are isomorphous as are those of metal hydrazine complexes of cobalt, zinc and cadmium.     

Electrochemiluminescence in the reduction of uranyl ions on platinum in sulfuric acid solutions

Electrochemiluminescence (ECL) accompanying the reduction of uranyl ions on a platinum cathode in sulfuric solutions in the presence of XeO₃ was observed and studied. At early stages of the electrolysis (at 0.34<φ<0.62 V), the chemiluminescence reaction U^V+XeO₃ contributes mainly to the luminescence intensity, whereas at φ<0.32 V, the contribution of the reaction U^IV+XeO₃ predominates. The transfer coefficient for the primary electrochemical stage, formation of U^V, was estimated: α=0.46−0.54. The high sensitivity of ECL to the state of the electrode surface is explained by the fact that the reduction of U^VI occurs on the most active sites only. the background chemiluminescence reactions, among which U^V+O₂ and U^V+H₂O₂ can be distinguished, were considered, and their contributions to ECL were determined. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1928–1934, October, 1999.     

Interactions of Some Amino Acids with Aqueous N,N-Dimethylacetamide Solutions at 298.15 and 308.15 K: A Volumetric Approach

The apparent molar volumes, V _φ , of glycine, L-alanine and L-serine were obtained in aqueous 0 to ∼4 mol⋅kg⁻¹ N,N-dimethylacetamide (DMA) solutions from density measurements at 298.15 and 308.15 K. The standard partial molar volume, V _φ ^o, and standard partial molar volumes of transfer, Δ_tr V _φ ^o, were determined for these amino acids. It has been shown that hydrophilic-hydrophilic interactions between charged groups of the amino acids and the —CON= group of DMA are predominant in the case of glycine and L-serine, but for L-alanine the interactions between its side group (—CH₃) and DMA are predominant. An increase in temperature increases the standard partial molar volumes but decreases the transfer volumes of the amino acids. The results have been interpreted in terms of cosphere overlap model.     

D<Subscript>2</Subscript>O — H<Subscript>2</Subscript>O Solvent Isotope Effects on the Apparent Molar Volumes of Tetramethyl-<Emphasis Type="Italic">bis</Emphasis>-urea (Mebicarum) Solutions

Densities of solutions of tetramethyl-bis-urea (TMbU) or “Mebicarum” in H₂O and D₂O, with solute mole fraction concentrations (x ₂) ranging up to 3.2 × 10⁻³, have been measured at 288.15, 298.15, 308.15 and 318.15 K using a precision vibrating-tube densimeter. The limiting apparent molar volumes, V _φ,2 ^∞, and expansibilities, E _{p, φ, 2} ^∞, of the solute have been calculated. The isotope effect δ V _φ,2 ^∞(H₂O → D₂O;T) is negative, monotonously decreases in magnitude with temperature and reverses sign at T ≈ 318 K. Water (H₂O, D₂O) and TMbU molecules in infinitely- and highly-dilute aqueous solutions form H(D)-bonded hydration complexes with a high packing density. The hydration of TMbU should be treated as a superposition of two mechanisms, hydrophobic and hydrophilic, with the latter one predominating.     

Densities and Apparent Molar Volumes of NaOH(aq) to the Temperature 623 K and Pressure to 30 MPa

Densities of NaOH(aq) solutions with molalities between 0.033 and 6.047 mol⋅kg⁻¹ were measured with a vibrating-tube densitometer at temperatures between 373 K and 623 K and pressures from near the saturation vapor pressure of water to 30 MPa. Apparent molar volumes, V _φ, calculated from the measured densities in this work were well represented with the Pitzer ion-interaction treatment up to T = 523 K. Above that temperature the formation of ion pairs must be taken into account to describe correctly the molality dependence of V _φ and for the reliable extrapolation of V _φ to infinite dilution. Standard-state thermodynamic properties for the ion formation reaction were taken from recently published electrical conductivity measurements. A comparison with previous correlations of volumetric properties of NaOH(aq) is presented covering the full range of pressure and temperature.     

Selective Pseudo-Rotaxane Type Complex Formation of Zinc(II) (t-butylatedtetraphenyl) porphyrin-Viologen Linked Compounds with tri-O-methyl-β-Cyclodextrin

Inclusion complexation behavior of 2,3,6−tri-O-methyl-β-cyclodextrin (TM-β-CD) with zinc(II) 5,10,15-tri-(4-t-butyl-phenyl)-20-(4-(n-alkyloxy)phenylporphyrin covalently linked with violgen by a polymethylene chain (Zn-t- bu-PC _n V²⁺; n=4, 6, 8, 10 and 12) was investigated by means of ¹H NMR, UV/Vis absorption spectroscopies in acetonitrile-water (1:1, v/v). The ¹H NMR spectra indicated that Zn-t-bu-PC _n V²⁺ presumably existed as a mixture of a dimer and a monomer in high concentration (>1×10⁻³ mol dm⁻³), and the dimer was degraded by the complex formation with TM-β-CD. The ¹H NMR spectra of these compounds as a function of [TM-β-CD] showed the selective formation of 1:1 (=Zn-t-bu-PC _n V²⁺: TM-β-CD) pseudo-rotaxane type complexes. The chemical modification by t-butyl groups on porphyrin showed a good protective effect on inclusion of benzene groups into the TM-β-CD cavity. These rotaxane formation constants (K) were determined by titration studies using UV/Vis absorption spectroscopy. These complex formation constants were somewhat affected by the spacer methylene chain between the porphyrin and viologen. The value of K for Zn-t-bu-PC₄V²⁺·TM-β-CD is 1.0×10³ M⁻¹ which is the smallest whereas those for Zn-t-bu-PC _n V²⁺·TM-β-CD (n=8, 10, 12) were similar (1.0×10⁴ M⁻¹).     

New Complexes of Rare Earth Elements with 3-Methyladipic Acid

Rare earth element 3-methyladipates were prepared as crystalline solids with general formula Ln₂(C₇H₁₀O₄)₃⋅nH₂O, where n=6 for La, n=4 for Ce,Sm–Lu, n=5 for Pr, Nd and n=5.5 for Y. Their solubilities in water at 293 K were determined (2⋅10^–3–1.5⋅10^–4 mol dm^–3). The IR spectra of the prepared complexes suggest that the carboxylate groups are bidentate chelating. During heating the hydrated 3-methyladipates lose all crystallization water molecules in one (Ce–Lu) or two steps (Y) (except of La(III) complex which undergoes tomonohydrate) and then decompose directly to oxides (Y, Ce) or with intermediate formation of oxocarbonates Ln₂O₂CO₃ (Pr–Tb) or Ln₂O(CO₃)₂ (Gd–Lu). Only La(III) complex decomposes in four steps forming additionally unstable La₂(C₇H₁₀O₄)(CO₃)₂. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and characteristics of novel pentanuclear complexes [(OC)3Mn(η1,η5-C5H4)Fe(CO)2(η1,η5-C5H4CO2)]2M(η5-C5H5)2 (M=Ti, Zr)

The reaction of Cp₂MCl₂ complexes (M=Ti and Zr) with 2 equiv. of (OC)₃Mn(η¹,η⁵-C₅H₄)Fe(CO)₂(η⁵-C₅H₄COONa) results in the formation of the pentanuclear complexes (OC)₃Mn(η¹,η⁵-C₅H₄)Fe(CO)₂(η⁵-C₅H₄CO₂)]₂M(η⁵-C₅H₅)₂, which are characterized by IR and¹H NMR spectroscopy and cyclic voltammetry. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 1055–1058, May, 1997.     

Vacancy Contents in MnZn Ferrites From TG Curves

Expressions for calculating the cation vacancy contents of MnZn ferrites from thermogravimetric curves are presented together with some experimental data. In a single-phase MnZn ferrite synthesized by conventional ceramic procedures, the O₂ evolution accompanying ferrite formation follows the formal equation. Mn²⁺ _σα Zn_σβ Fe³⁺ _2σ(1–γ) [V ]_{σ/4(1–2γ)} O₄ =σ'/σ Mn²⁺ _σ(α–2ϕ) Zn_σβ Fe²⁺ _2σθ Mn³⁺ _2σϕ Fe³⁺ _{2σ(1–γ–θ)} [V ]_{σ/4(1–2γ–3ϕ)} O₄ +σ'φ/2O₂ (g) where α and β denote the MnO and ZnO mole fractions in the primary mixture γ=α+β, θ and ϕ depend on the quantities of Fe²⁺ and Mn³⁺ formed, respectively, φ=θ–ϕ and σ'/σ is a function of the former parameters. Even though the relative amounts of Fe²⁺ /Fe³⁺ and Mn²⁺ /Mn³⁺ remain uncertain, the vacancy content [V ] of the ferrite can be determined because it depends on φ alone, which is related to the change in mass of the sample as the synthesis takes place through the equation φ=(1.5–γ) μ_β /μ_O2 (1–m _f /m _i ) Here, m _i and m _f are the masses of the sample before and after O₂ evolution, μ_B is the formula mass of the ferrite and μ_O2 is the O₂ molar mass. Practically vacancy-free single-phase MnZn ferrite samples were obtained by sintering in air at 1250°C and cooling in pure N₂ . This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and crystal structure of the Sm(ButNCHCHNBut)2(bpy) complex

Reaction of Sm(bpy)₄ (bpy is 2,2′-bipyridyl) with di-tert-butyldiazabutadiene (dad) in tetrahydrofuran (THF) affords the mixed-ligand complex Sm(dad)₂(bpy) (1). Complex1 was isolated as black paramagnetic crystals readily soluble in THF, 1,2-dimethoxyethane (DME), toluene, and ether. Compound1 was characterized by IR and ESR spectroscopy, X-ray diffraction analysis, and by the results of magnetic measurements. Based on the difference between the Sm−N bond lengths and on the data of IR spectroscopy, the following formal charge distribution in the molecule of complex1 was proposed: Sm³⁺(dad)²⁻(dad)¹⁻(bpy)⁰. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1860–1862, October. 1997.     

Hydrolytic precipitation of magnesium polyvanadates in vanadium (IV, V) solutions

The phase and chemical composition of precipitates formed in Mg(VO₃)₂-VOSO4-H₂O system at initial pH from 1 to 7 and temperature from 80 to 90°C was studied. Polyvanadates of variable composition Mg _x V _y ⁴⁺V_12-y ⁵⁺¹O_31–δ · nH₂O (0.7 ≤ x ≤ 1.3, 1.2 ≤ y ≤ 2.4, 0.7 ≤ δ = 1.4) were formed at pH from 1 to 4 and V⁴⁺/V⁵⁺ ratio from 0.43 to 9. Compounds with the general formula Mg _x V _y ⁴⁺V_6-y ⁵⁺O_16-δ · nH₂O (0.7 ≤ x ≤ 0.65, y = 1.0, 0.8 ≤ δ ≤ 0.85) were formed at pH from 6.0 to 7.0 and V⁴⁺/V⁵⁺ ratios from 0.11 to 0.25. The maximum V⁴⁺ concentration (y = 2.4) in the precipitates was achieved at the VV⁴⁺/V⁵⁺ solution ratio of 1.0 and pH = 3. The precipitates in solutions with pH 3 were formed only upon addition of VO²⁺ ions with the maximum rate at a V⁴⁺/V⁵⁺ ratio of 0.33. These processes were limited by second-order reactions on the surface of polyvanadates.     

Complexes of (ω-diphenylphosphinoalkyl)diphenylphosphine sulfides with silver nitrate in pyridine

The behavior of the phosphine-phosphine sulfide complexes of silver, [Ph₂P(S)(CH₂) _n PPh₂] _m ·AgNO₃ (n=2 or 4;m=1 or 2), in pyridine was studied. Dissolution of the 1:1 complexes in pyridine leads to destruction of their dimeric structures Ag₂[Ph₂P(S)(CH₂) _n PPh₂]₂(NO₃)₂ (A) to form the complexes Agp_y ⁺−P(Ph₂)(CH₂) _n Ph₂P=S and Agp_y ⁺−S=PPh₂(CH₂) _n PPh₂. The solid complexes isolated from pyridine restore dimeric structure A. According to the data of X-ray diffraction analysis, the 1:2 complex isolated from pyridine has the structure [S=P(Ph₂)(CH₂)₂(Ph₂)P−(NO₃)Ag(Py)−P(Ph₂) (CH₂)₂(Ph₂)P=S]Py. According to the data of IR spectroscopy, dissolution of this complex in chloroform leads to the formation of the dimeric structure Ag₂Ph₂P(S)(CH₂)₂PPh₂]₄(NO₃)₂. Deceased. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 9, pp. 1751–1758, September, 1998.     

Study of the Volumetric Properties of the Aqueous Ionic Liquid 1-Methyl-3-pentylimidazolium Tetrafluoroborate

This paper reports the densities of aqueous solutions of the ionic liquid (IL) 1-methyl-3-pentylimidazolium tetrafluoroborate ([pmim][BF₄]) that were measured from 278.15 to 343.15 K, at intervals of 5 K, using an Anton Parr model DMA 4500 oscillating U-tube densitometer. The apparent molar volume, ^φ V _B, and the partial molar volume of [pmim][BF₄], , were calculated. The values of the apparent molar volume, ^φ V _B, were fitted to Pitzer’s model for volumetric properties by the method of least-squares, which allowed the partial molar volume of the IL at infinite dilution, , and Pitzer’s parameters, β _M,X ^(0)V and β _M,X ^(1)V , to be obtained. The small standard deviations of the fits show that Pitzer’s model is also appropriate for representing the volumetric properties of aqueous solutions of the ionic liquid [pmim][BF₄].