Competition between chalcogen bond and halogen bond interactions in YOX<Subscript>4</Subscript>:NH<Subscript>3</Subscript> (Y = S,Se; X = F,Cl, Br) complexes: An ab initio investigation

Using ab initio calculations, the geometries, interaction energies and bonding properties of chalcogen bond and halogen bond interactions between YOX₄ (Y = S, Se; X = F, Cl, Br) and NH₃ molecules are studied. These binary complexes are formed through the interaction of a positive electrostatic potential region (σ-hole) on the YOX₄ with the negative region in the NH₃. The ab initio calculations are carried out at the MP2/aug-cc-pVTZ level, through analysis of molecular electrostatic potentials, quantum theory of atoms in molecules and natural bond orbital methods. Our results indicate that even though the chalcogen and halogen bonds are mainly dominated by electrostatic effects, but the polarization and dispersion effects also make important contributions to the total interaction energy of these complexes. The examination of interaction energies suggests that the chalcogen bond is always favored over the halogen bond for all of the binary YOX₄:NH₃ complexes.     

A theoretical investigation on the structures and stabilities of C<Subscript>60</Subscript>X<Subscript>18</Subscript> and C<Subscript>70</Subscript>X<Subscript>10</Subscript> (X = H,F, Cl,and Br)

A density functional theory study was performed on fullerene derivatives C₆₀X₁₈ and C₇₀X₁₀ (X = H, F, Cl, and Br). The calculated results show that the lowest energy isomers are IPR-satisfying for C₆₀X₁₈ (X = H, F, Cl, and Br). It is found that the addition patterns of X (X = Cl and Br) are different from those of X (X = H and F) for C₆₀, demonstrating that the stability of fullerene derivatives is partly attributed to the steric repulsion and electronegativity of added atoms. However, the lowest energy isomers are IPR-violating for C₇₀X₁₀ (X = H, F, and Cl), suggesting that many more fullerene derivatives may violate the isolated pentagon rule.     

Crystal structure and vibrational spectra of M[VO<Subscript>2</Subscript>(SeO<Subscript>4</Subscript>)(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]·H<Subscript>2</Subscript>O (M = K,Rb, NH<Subscript>4</Subscript>)

By the hydration of MVO(SeO₄)₂ with saturated water vapors at room temperature a series of isostructural complex compounds of vanadium(V) of the composition M[VO₂(SeO₄)(H₂O)₂]·H₂O (K, Rb, NH₄) are synthesized and their physicochemical properties are studied. Based on the X-ray and neutron diffraction data, it is found that their crystal structure is composed of VO₆ octahedra linked in infinite chains by bridging SeO₄ tetrahedra. Each of the VO₆ octahedra has two short terminal V-O bonds forming a bent dioxovanadium group VO₂⁺. Two water molecules are coordinated by vanadium and one molecule is out of the first coordination sphere in the interchain space. The vibrational spectra of the studied compounds are completely consistent with their structural features.     

The mutual influence between <Emphasis Type="Italic">π</Emphasis>-hole pnicogen bonds and <Emphasis Type="Italic">σ</Emphasis>-hole halogen bonds in complexes of PO<Subscript>2</Subscript>Cl and XCN/C<Subscript>6</Subscript>H<Subscript>6</Subscript> (X = F,Cl, Br)

The bimolecular and termolecular complexes involving PO₂Cl and XCN/C₆H₆ (X = F, Cl, Br) were designed to form the π-hole pnicogen bonds and σ-hole halogen bonds, to compare the two types of interactions and investigate the mutual influences between them. PO₂Cl was used as simultaneous π-hole and σ-hole donor; it can interact with electron donor to form π-hole pnicogen bond and σ-hole halogen bond. The π-hole interactions are stronger than the σ-hole interactions, in both the bimolecular and the termolecular complexes. Comparing the mutual effects of the π-hole interactions and σ-hole interactions, the π-hole interaction has a greater influence on the σ-hole interaction than vice versa. With the addition of σ-hole halogen bond, the V _S,max value outside the π-hole region of PO₂Cl becomes decreasingly positive, resulting in a weaker π-hole interaction. With the addition of π-hole pnicogen bond, the V _S,max value outside the σ-hole region of PO₂Cl becomes small, also resulting in a weaker σ-hole interaction. The π-hole pnicogen bond and σ-hole halogen bond weaken each other, i.e., there is a negative cooperative effect in the termolecular complexes.     

Hydrogen abstraction reactions of OH radicals with CF<Subscript>2</Subscript>ClCClXH (X = F,Cl) and CFCl<Subscript>2</Subscript>CClXH (X = F,Cl): a mechanistic and kinetic study

The reactions of OH (OD) radicals with CF₂ClCClFH (R1), CF₂ClCCl₂H (R2), CFCl₂CClFH (R3), and CFCl₂CCl₂H (R4) have been investigated theoretically by a dual-level direct dynamics method. The optimized geometries and frequencies of the stationary points are calculated at the MPW1K/6-311+G(d,p) level. To improve the reaction enthalpy and potential barrier of each reaction channel, the single-point energy calculation is made by the MC-QCISD method. The enthalpies of formation of the species CF₂ClCClFH, CF₂ClCCl₂H, CFCl₂CClFH, CFCl₂CCl₂H, CF₂ClCClF, CF₂ClCCl₂, CFCl₂CClF, and CFCl₂CCl₂ are evaluated by two sets of isodesmic reactions. Using canonical variational transition state theory (CVT) with the small-curvature tunneling correction (SCT) method, the rate constants of OH and OD radicals with CF₂ClCClXH (X = F, Cl) and CFCl₂CClXH (X = F, Cl) are evaluated over a wide temperature range of 100–2,000 K at the MC-QCISD//MPW1K/6-311+G(d,p) level. The calculated CVT/SCT rate constants are consistent with available experimental data. The results show that the tunneling correction has an important contribution in the calculation of rate constants at lower temperatures. For the above-mentioned four reactions, the kinetic isotope effects are also calculated. Finally, the effect of fluorine or chlorine substitution on reactivity of the C–H bond is discussed.     

Synthesis and crystal structure of [Cr(NH<Subscript>3</Subscript>)<Subscript>5</Subscript>Cl][PdCl<Subscript>4</Subscript>]·H<Subscript>2</Subscript>O

Synthesis and investigation of a binary complex salt [Cr(NH₃)₅Cl][PdCl₄]·H₂O is reported. The compound is isostructural with [Rh(NH₃)₅Cl][PdCl₄]·H₂O studied earlier; it was characterized by element analysis and powder and single crystal X-ray diffraction. Crystal data for H₁₇Cl₅N₅OPdCr: a = 7.8668(12) Å, b = 10.9703(16) Å, c = 16.048(2) Å, = 102.469(3)°, space group P2₁/c, Z = 4, V = 1352.3(3)ų, d _calc = 2.155 g/cm³.Original Russian Text Copyright © 2004 by I. A. Baidina, P. E. Plyusnin, S. V. Korenev, K. V. Yusenko, Yu. V. Shubin, and S. A. GromilovTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 549–552, May–June 2004.     

Characterization of <Emphasis Type="Italic">σ</Emphasis>-hole interactions in 1:1 and 1:2 complexes of YOF<Subscript>2</Subscript>X (X = F,Cl, Br,I; Y = P,As) with ammonia: competition between halogen and pnicogen bonds

Ab initio calculations at the MP2/aug-cc-pVTZ level of theory are performed to examine 1:1 and 1:2 complexes of YOF₂X (X = F, Cl, Br, I; Y = P, As) with ammonia. The YOF₂X:NH₃ complexes are formed through the interaction of the lone pair of the ammonia with the σ-hole region associated with the X or Y atom of YOF₂X molecule. The calculated interaction energies of halogen-bonded complexes are between ?1.06 kcal/mol in the POF₃···NH₃ and ?6.21 kcal/mol in the AsOF₂I···NH₃ one. For a given Y atom, the largest pnicogen bond interaction energy is found for the YOF₃, while the smallest for the YOF₂I one. Almost a strong linear relationship is evident between the interaction energies and the magnitudes of the positive electrostatic potentials on the X and Y atoms. The results indicate that the interaction energies of halogen and pnicogen bonds in the ternary H₃N:YOF₂X:NH₃ systems are less negative relative to the respective binary systems. The interaction energy of Y···N bond is decreased by 1–22 %, whereas that of X···N bond by about 5–61 %. That is, both Y···N and X···N interactions exhibit anticooperativity or diminutive effects in the ternary complexes.     

<Superscript>35</Superscript>Cl NQR for the SbCl<Subscript>3</Subscript> complex with aniline,SbCl<Subscript>3</Subscript>·NH<Subscript>2</Subscript>C<Subscript>6</Subscript>H<Subscript>5</Subscript>

The temperature dependence of the ³⁵Cl NQR frequencies and spin-lattice relaxation times has been investigated for a trigonal-bipyramidal vn complex SbCl₃·NH₂C₆H₅. Thermally activated motion of chlorine atoms (pseudorotation) was not revealed in the complex, in contrast to the vπ complexes of SbCl₃ with related molecular structures. The high potential barrier of pseudorotation in the aniline complex is likely to be due to the unusually high nonequivalence of Sb-Cl chemical bonds.     

Synthesis and crystal structures of [K(H<Subscript>2</Subscript>O)(Piv)]<Subscript>∞</Subscript> and [K<Subscript>2</Subscript>(Phen)(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>(Piv)<Subscript>2</Subscript>]<Subscript>∞</Subscript>

A method for the synthesis of potassium pivalates (trimethylacetates) from potassium tert-butoxide and pivalic acid was proposed. The complexes of the formulas [K(H₂O)(Piv)]_∞(I) and [K₂(Phen)(H₂O)₂(Piv)₂]_∞ (II) (Piv denotes the pivalate anion and Phen denotes 1,10-phenanthroline) were obtained and characterized by elemental analysis and IR and ¹H NMR spectroscopy. The crystal structures of complexes I and II were determined using X-ray diffraction. Crystal structure I has a layered motif with two nonequivalent K atoms (C.N.s 5 + 2 and 6). The coordination of phenanthroline in II gives rise to a ribbon motif, the structure containing three nonequivalent K atoms (C.N.s 6, 6 + 1, and 8).     

Solubility and stability of (NH<Subscript>4</Subscript>)<Subscript>2</Subscript>SO<Subscript>4</Subscript>·H<Subscript>2</Subscript>O<Subscript>2</Subscript> in organic and aqueous-organic media

Solubility and stability of (NH₄)₂SO₄·H₂O₂ in organic solvents (glycerol, ethylene glycol, TOSOL-A40 OM antifreeze), in mixtures of an organic solvent and water, and in pure water was studied. Crystallographic properties of the ammonium sulfate precipitating from aqueous-organic solvents and aqueous solutions in various time intervals and differing from ordinary (NH₄)₂SO₄ in solubility and one of crystallographic parameters were analyzed.     

Synthesis and crystal structure of the complex [Nd(2-EOBA)<Subscript>3</Subscript>(phen)(H<Subscript>2</Subscript>O)]<Subscript>2</Subscript> · H<Subscript>2</Subscript>O

A novel lanthanide complex of [Nd(2-EOBA)₃(phen)(H₂O)]₂ · H₂O (2-EOBA = 2-ethoxylbenzoate, phen = 1,10-phenanthroline), has been synthesized and structurally characterized by single crystal X-ray diffraction. The complex crystallizes in monoclinic, space group P2(1)/n with a = 14.7453(18) Å, b = 12.3628(15) Å, c = 19.473(2) Å, α = 90°, β = 93.349(2)°, γ = 90°. Two Nd³⁺ ions are connected together by two bridging 2-EOBA ligands and each Nd³⁺ ion is further coordinated by two chelating 2-EOBA ligands, one chelating phen molecule and one water molecule. The coordination number of Nd³⁺ ion is nine. The coordination geometry of Nd³⁺ ion is a distorted monocapped square-antiprism.     

Phase transformations in the systems Ti<Subscript>2</Subscript>Fe–H<Subscript>2</Subscript> and Ti<Subscript>2</Subscript>Fe–NH<Subscript>3</Subscript>

The interactions of two-phase alloy Ti₂Fe with hydrogen and ammonia at 100–500°C were studied, the compositions of the products were found, and the conditions for producing hydride and nitride phases were determined. The potential of using the two-phase alloy in a metal hydride hydrogen accumulator operating at 20–600°C was considered.     

Synthesis and Crystal Structure of Nitrotriammine Complex of Nitrosoruthenium(II) [RuNO(NH<Subscript>3</Subscript>)<Subscript>3</Subscript>(NO<Subscript>2</Subscript>)(OH)]Cl·0.5H<Subscript>2</Subscript>O

Procedures for the synthesis of the [RuNO(NH_{3 3}(NO₂)(OH)]Cl·0.5H₂O complex have been developed. The compound was investigated by IR spectroscopy, and also by powder and single crystal X-ray diffraction. Crystal data for H₁₁CIN₅O_4.5Ru: a = 6.5752(7) Å, b = 11.0900(18) Å, c = 12.296(2) Å, ά = 79.692(13)°, β = 85.088(11)°, γ = 87.395(11)°, V = 878.5(2) ų, Z = 4, d _calc = 2.190 g/cm³, space group . The structure is formed by [RuNO(NH₃)₃(NO₂)(OH)]⁺] complex cations, Cl⁻ anions, and crystallization water molecules. The complex crystallizes as yellow transparent prisms belonging to the triclinic crystal system; it is soluble in water and insoluble in ethanol and acetone. The crystals are stable when kept in a closed beaker, but gradually degrade in dry air.Original Russian Text Copyright © 2004 by V. A. Emel’yanov, S. A. Gromilov, and I. A. Baidina__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 5, pp. 923–932, September–October, 2004.     

Reaction of [Pt(NH<Subscript>3</Subscript>)<Subscript>4</Subscript>]Cl<Subscript>2</Subscript>·H<Subscript>2</Subscript>O and NH<Subscript>4</Subscript>ReO<Subscript>4</Subscript> in alkaline aqueous solution at 190°C (under pressure)

Reactions of thermolysis under pressure of tetraammineplatinum(II) chloride and ammonium perrhenate in alkaline aqueous solution were studied. The products formed at the thermolysis in a pressure reactor were investigated. A model of platinum and rhenium ions reduction to metallic state by inner sphere ammonia from [Pt(NH₃)₄]Cl₂ is suggested.     

Structure and thermal properties of double complex salts [RuNO(NH<Subscript>3</Subscript>)<Subscript>4</Subscript>(H<Subscript>2</Subscript>O)]<Subscript>2</Subscript>[MCl<Subscript>4</Subscript>]Cl<Subscript>4</Subscript>·2H<Subscript>2</Subscript>O,M = Pt,Pd

Double complex salts (DCS) [RuNO(NH₃)₄(H₂O)]₂[MCl₄]Cl₄·2H₂O, M = Pt (I) and Pd (II), are prepared and characterized using IR spectroscopy, single crystal and powder X-ray diffraction, and thermogravimetric analysis. Crystalline phases of I and II are isostructural (P2(1)/n space group) and have the following crystallographic characteristics: a = 6.689 Å, b = 15.609 Å, c = 12.348 Å, V = 1289.1 ų, Z = 2, d _x = 2.425 g/cm³ (I) and a = 6.637 Å, b = 15.521 Å, c = 12.244 Å, V = 1261.2 ų, Z = 2, d _x = 2.255 g/cm³ (II). The thermolysis of the obtained DCS in the hydrogen atmosphere affords two-phase mixtures of limited solid solutions of the metals: hcp for ruthenium-based ones and fcc for Pt or Pd based solutions. On decomposition in the helium atmosphere the products contain a minor amount of RuO₂. For the phases obtained during thermolysis the parameters are determined and the compositions are estimated. The heating of I to 400°C in the helium-air atmosphere yields a nanocrystalline composite Pt+RuO₂ with CSR of ～20 nm.     

Crystal structure,infrared and raman spectra of tripotassium trisaccha-rinate dihydrate,K<Subscript>3</Subscript>(C<Subscript>7</Subscript>H<Subscript>4</Subscript>NO<Subscript>3</Subscript>S)<Subscript>3</Subscript>·2H<Subscript>2</Subscript>O

The crystal structure of tripotassium trisaccharinate dihydrate, K₃(C₇H₄NO₃S)₃·2H₂O, is triclic, space group\(P \bar 1, Z = 2\). It consists of three crystallographically independent potassium and saccharinato ions as well as two structurally different water molecules. Potassium coordination polyhedra are irregular, with K1 and K3 six-coordinated and the third one K2 seven-coordinated. The K?O distances range from 2.652(9) to 3.100(2) Å(mean: 2.790 Å) whereas the K?N distance is 3.025(3) Å. The water molecules W2 is disordered over three positions with occupancies of approximately 0.6, 0.2 and 0.2. The hydrogen atom (H1W1) of the ordered water molecule (O1W) is hydrogen bonded to the sulfonyl oxygen atom (O11) (R(O...O)=2.976(3) Å), whereas the other hydrogen atom (H2W1) is bifurcated to the carbonyl oxygen atom (O13) (R(O...O)=2.851(3) Å) and the disordered water molecules (O23W) (R(O...O)=3.067(12) Å). The carbonyl oxygens (O13, O23 and O33) and one of the disordered water molecules (O22W) are involved in C?H...O hydrogen bonds (R(C?H...O)=3.027(4)–3.304(9) Å). Structural characteristics of the studied compound are compared with the analogous trisodium trisaccharinate dihydrate and dipotassium sodium trisaccharinate monohydrate. Infrared and Raman spectra of the title compound have been analyzed in relation to the structure, and compared with the spectra of trisodium trisaccharinate dihydrate.     

Physicochemical properties of (CH<Subscript>3</Subscript>)<Subscript>2</Subscript>NH<Subscript>2</Subscript>Cl–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites

Composite solid electrolytes were synthesized from the organic salt dimethylammonium chloride (1–x)C₂H₈NCl–xAl₂O₃. Their physicochemical properties were studied. In the starting C₂H₈NCl salt, there is a phase transition at 39°C accompanied by an increase in conductivity by two orders of magnitude. The conductivity of the high-temperature phase is 9.3 × 10^–6 S/cm at 160°C. A differential scanning calorimetry study showed that the salt in the composites spreads over the oxide surface and at x > 0.6 the salt melting enthalpy decreases to zero. The conductivity of the resulting composites was studied by impedance spectroscopy. It was shown that heterogeneous doping leads to a sharp increase in ion conductivity to 7.0 × 10^–3 S/cm at 160°C and a decrease in the activation energy to 0.55 eV.     

Polytherm of the CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>–KNO<Subscript>3</Subscript>–H<Subscript>2</Subscript>O phase diagram

The crystallization polytherm of the ternary CO(NH₂)₂–KNO₃–H₂O system is plotted for the first time via visual polythermal analysis and calculating ternary eutonics characteristics from data on the boundary elements of two-component systems. The ternary eutonics modeling error does not exceed 3.5%. In addition to the crystallization fields of individual components, the field of the redox reaction that occurs in the system between potassium nitrate and carbamide is shown in the CO(NH₂)₂–KNO₃–H₂O diagram by a dashed outline.     

Kinetics and thermodynamics of thermal decomposition of NH<Subscript>4</Subscript>NiPO<Subscript>4</Subscript>·6H<Subscript>2</Subscript>O

The single phase NH₄NiPO₄·6H₂O was synthesized by solid-state reaction at room temperature using NiSO₄·6H₂O and (NH₄)₃PO₄·3H₂O as raw materials. XRD analysis showed that NH₄NiPO₄·6H₂O was a compound with orthorhombic structure. The thermal process of NH₄NiPO₄·6H₂O experienced three steps, which involves the dehydration of the five crystal water molecules at first, and then deamination, dehydration of the one crystal water, intramolecular dehydration of the protonated phosphate groups together, at last crystallization of Ni₂P₂O₇. In the DTA curve, the two endothermic peaks and an exothermic peak, respectively, corresponding to the first two steps’ mass loss of NH₄NiPO₄·6H₂O and crystallization of Ni₂P₂O₇. Based on Flynn–Wall–Ozawa equation, and Kissinger equation, the average values of the activation energies associated with the thermal decomposition of NH₄NiPO₄·6H₂O, and crystallization of Ni₂P₂O₇ were determined to be 47.81, 90.18, and 640.09 kJ mol⁻¹, respectively. Dehydration of the five crystal water molecules of NH₄NiPO₄·6H₂O, and deamination, dehydration of the crystal water of NH₄NiPO₄·H₂O, intramolecular dehydration of the protonated phosphate group from NiHPO₄ together could be multi-step reaction mechanisms. Besides, the thermodynamic parameters (ΔH ^≠, ΔG ^≠, and ΔS ^≠) of the decomposition reaction of NH₄NiPO₄·6H₂O were determined.