σ-Hole bond tunability in YO<Subscript>2</Subscript>X<Subscript>2</Subscript>:NH<Subscript>3</Subscript> and YO<Subscript>2</Subscript>X<Subscript>2</Subscript>:H<Subscript>2</Subscript>O complexes (X = F,Cl, Br; Y = S,Se): trends and theoretical aspects

A σ-hole is defined as an electron-deficient region on the extension of a covalently bonded group IV–VII atoms. If the electronic density in the σ-hole is sufficiently low, then this region will have a positive electrostatic potential, which allows attractive noncovalent interactions with negative sites. SO₂X₂ and SeO₂X₂ (X = F, Cl and Br) have three Lewis acid sites of σ-hole located in the outermost of chalcogen atom and X end, participating in the chalcogen and halogen bonds with NH₃ and H₂O, respectively. MP2/aug-cc-pVTZ and M06-2X/aug-cc-pVTZ calculations reveal that for a given halogen atom, SeO₂X₂ forms stronger chalcogen bond interactions than SO₂X₂ counterpart. Almost a perfect linear relationship is evident between the interaction energies and the magnitudes of the product of most positive and negative electrostatic potentials. The interaction energies calculated by M06-2X and MP2 methods are almost consistent with each other.     

Exohedral Silicon Fullerenes: Si<Subscript>60</Subscript>Pn<Subscript>60</Subscript> and Si<Subscript>80</Subscript>Pn<Subscript>60</Subscript> (Pn = P,As, Sb and Bi)

Based on density functional theory (DFT) calculations, we predict that the icosahedral structures of the silicon fullerenes Si₆₀ and Si₈₀ can be stabilized by 12 exohedral pentagons of group V-A unit Pn₅ (Pn = P, As, Sb or Bi). The 12 pentagons can fully passivate the dangling bonds associated with 12 pentagonal Si₅ rings on the silicon fullerene cages, thereby resulting in stable exohedral silicon fullerenes Si₆₀Pn₆₀ and Si₈₀Pn₆₀. Properties of the eight Si₆₀Pn₆₀ and Si₈₀Pn₆₀ clusters, including harmonic vibrational frequencies, electron affinity (EA), the HOMO–LUMO gap and NICS values, are computed. We find that all eight Si₆₀Pn₆₀ and Si₈₀Pn₆₀ fullerenes possess relatively large HOMO–LUMO gaps, high electron affinities, and that the Si₆₀Pn₆₀ fullerenes exhibit weak aromaticity. Among eight clusters examined, the exohedral fullerene I _h-Si₆₀P₆₀ possesses the largest cohesive energy per atom. Ab initio molecular dynamics (AIMD) simulation is performed to demonstrate thermal stability of the hollow cage structure of Si₆₀P₆₀ at the room temperature.     

Synthesis and Characterization of the Face-Centered Cubic Clusters [(Me<Subscript>3</Subscript>tacn)<Subscript>8</Subscript>M<Subscript>8</Subscript>Pt<Subscript>6</Subscript>(CN)<Subscript>24</Subscript>]<Superscript>12+</Superscript> (M = Cr,Mo)

Incorporation of a 5d transition metal into the face-centered cubic metal-cyanide cluster geometry is accomplished for the first time with the isolation of a series of compounds featuring [(Me₃tacn)₈M₈Pt₆(CN)₂₄]¹²⁺ (M = Cr, Mo) clusters. Reaction of [(Me₃tacn)Cr(CN)₃] and K₂[PtCl₄] in a boiling aqueous solution generates [(Me₃tacn)₈Cr₈Pt₆(CN)₂₄]Cl₁₂ · 27H₂O (1), wherein Pt^II centers reside at the face-centering sites and the cyanide ligands have reoriented to give Pt^II–C≡N–Cr^III linkages. The cyclic voltammogram obtained for a solution of 1 in DMSO exhibits a quasireversible reduction event centered at E _1/2 = ?1.59 V versus Cp₂Fe^0/1+. Reaction of 1 with K₂[Pt(CN)₄] in aqueous solution affords [(Me₃tacn)₈Cr₈Pt₆(CN)₂₄][Pt(CN)₄]₆ · 6H₂O (2), in which each face of the cubic cluster is capped by a staggered tetracyanoplatinate anion with a Pt–Pt separation of 3.1552(7) Å. Attempts to perform analogous cluster-forming reactions with [(Me₃tacn)Mo(CN)₃] revealed a tendency toward cluster decomposition to give mixtures of insoluble products, including [(Me₃tacn)₈Mo₈Pt₆(CN)₂₄][Pt(CN)₄]₆ · 46H₂O (3) and [(Me₃tacn)₈Mo₈Pt₆(CN)₂₄][Pt(CN)₄]_2.5[Pt(CN)₃Br]₂Br₃ · 6H₂O (4). Crystallographic analyses revealed these compounds to contain the anticipated [(Me₃tacn)₈Mo₈Pt₆(CN)₂₄]¹²⁺ cluster in fully- and partially-capped forms, respectively. Unfortunately, the insolubility of these molybdenum-containing products precluded characterization of the cluster by cyclic voltammetry.     

[Ca(OPPh<Subscript>3</Subscript>)<Subscript>5</Subscript>][Mo<Subscript>6</Subscript>(μ<Subscript>3</Subscript>-Cl)<Subscript>8</Subscript>Cl<Subscript>6</Subscript>] · OPPh<Subscript>3</Subscript>: Synthesis and crystal structure

A solvatothermal reaction of the octahedral cluster molybdenum complex (H₃O)₂[Mo₆(μ₃-Cl)₈Cl₆] · 6H₂O with CaCl₂ · 6H₂O and OPPh₃ in acetonitrile gave the known polymeric complex trans-[{Ca(OPPh₃)₄}{Mo₆(μ₃-Cl)₈Cl₆}]_∞. However, a closer examination revealed that this system also produces a novel cluster complex, [Ca(OPPh₃)₅][Mo₆(μ₃-Cl)₈Cl₆] · OPPh₃, which was isolated and characterized by X-ray diffraction.     

[H<Subscript>4</Subscript>(4,4′-Bipy)<Subscript>3</Subscript>][Sc(OH)(H<Subscript>2</Subscript>O)<Subscript>5</Subscript>]<Subscript>2</Subscript>Cl<Subscript>8</Subscript>: Synthesis,structure, and solid-phase thermal transformation

The reaction of [Sc(OH)(H₂O)₅]₂Cl₄ · 2H₂O in isopropanol with 4,4′-Bipy in CHCl₃ produced a crystalline compound, which was identified as [H₄(4,4′-Bipy)₃][Sc(OH)(H₂O)₅]₂Cl₈ (I) by elemental analysis, IR spectra, and single-crystal X-ray diffraction. In the structure of compound I, the three protonated diimine molecules form a centrosymmetric trimer via N...N hydrogen bonds. The polyhedron around the Sc atom is an octahedron with one split vertex. The excursion of the Sc atom from the plane formed by the oxygen atoms (water molecules) toward the hydroxo bridges is 0.5 Å. The thermolysis of compound I generates ScCl₃, whereas the final decomposition product of the precursor dimer is ScOCl.     

The R<Subscript>2</Subscript>Pd<Subscript>3</Subscript>Ge<Subscript>5</Subscript> (R = La–Nd,Sm) germanides: synthesis,crystal structure and symmetry reduction

Direct synthesis and structural characterization of a series of polar rare earth palladium germanides of R₂Pd₃Ge₅ composition (R = La–Nd, Sm) is reported. The crystal structure of the Nd representative was determined by single-crystal X-ray diffraction analysis (U₂Co₃Si₅-type, SG: Ibam, oI40, Z = 4, a = 10.1410(6), b = 12.0542(8), c = 6.1318(4) Å, wR ₂ = 0.0306, 669 F ² values, 31 variables). The crystal structures of the other homologues were ensured by powder X-ray diffraction pattern analysis. A smooth variation of the cell dimensions is observed through the rare earth series. The structure of the studied compounds can be interpreted as consisting of a complex three-dimensional [Pd₃Ge₅]^δ? network spaced by the rare earth cations. Within the concept of symmetry reduction, a Bärnighausen tree is used to rationalize the related crystal structures of the RPd₂Ge₂, RPdGe₃ and R₂Pd₃Ge₅ ternary compounds, enriching the large family of the BaAl₄ derivatives. Moreover, syntheses with metal fluxes were performed, some of which were successful to obtain large crystals of La₂Pd₃Ge₅ (using Bi as solvent) and Nd₂Pd₃Ge₅ (using Pb as solvent) stoichiometry.     

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.     

New double complex salt [PdEn<Subscript>2</Subscript>]<Subscript>3</Subscript>[Rh(NO<Subscript>2</Subscript>)<Subscript>6</Subscript>]<Subscript>2</Subscript> · 2.67H<Subscript>2</Subscript>O: Synthesis,crystal structure,and thermal properties

The crystal structure of the double complex salt (DCS) [PdEn₂]₃[Rh(NO₂)₆]₂ ? 2.67H₂O (I) has been determined by X-ray diffraction. Crystals are triclinic, space group \(P\bar 1\), Z = 4, a = 9.2331(3) Å, b = 9.9136(4) Å, c = 13.7824(5) Å, α = 84.3230(14)°, β = 89.9655(14)°, γ = 66.7272(13)°, V = 1152.19(7) ų, ρ_calcd = 2.141 g/cm³, R = 0.0279. The thermal behavior of complex salt I has been studied in various gas atmospheres. The end product of thermolysis in reductive atmosphere is a mixture of Pd_0.45Rh_0.55 and Pd_0.95Rh_0.05 solid solutions. The end product of thermolysis in an inert atmosphere is a homogeneous Pd_0.6Rh_0.4 solid solution.     

Mercury complex [(HOCH<Subscript>2</Subscript>)<Subscript>3</Subscript>CNH<Subscript>3</Subscript>]<Stack><Subscript>2</Subscript><Superscript>+</Superscript></Stack> [HgI<Subscript>4</Subscript>]<Superscript>2−</Superscript>: Synthesis and structure

The complex [(HOCH₂)₃CNH₃] ₂ ⁺ [HgI₄]^2? (I) was synthesized by reacting (trioxymethyl)methylammonium iodide with mercury dioide (2: 1 mol/mol) in acetone. X-ray crystallography shows that the complex consists of two types of crystallographically independent [(HOCH₂)₃CNH₃]⁺ cations and tetrahedral anions [HgI₄]^2? (IHgI, 106.49(2)°–113.99(4)°; Hg-I, 2.7849(8)-2.8105(8) Å. [(HOCH₂)₃CNH₃]⁺ cations are linked via hydrogen bonds O…H-N and O-H…N (O…N, 2.84–2.92 Å) to form polymer chains, which are cross-linked with one another via anions (I…H, 2.81, 2.82 Å).     

Crystal structure of Na<Subscript>3</Subscript>(NH<Subscript>4</Subscript>)<Subscript>2</Subscript>[Ir(SO<Subscript>3</Subscript>)<Subscript>2</Subscript>Cl<Subscript>4</Subscript>]·4H<Subscript>2</Subscript>O

The complex Na₃(NH₄)₂[Ir(SO₃)₂Cl₄]·4H₂O was examined with single crystal X-ray diffraction and IR spectroscopy. Crystal data: a = 7.3144(4) Å, b = 10.0698(5) Å, c = 12.3748(6) Å, β = 106.203(1)°, V = 875.26(8) ų, space group P2₁/c, Z = 2, d _calc = 2.547 g/cm³. In the complex anion two trans SO ₃ ^2? groups are coordinated to iridium through the S atom. The splitting of O-H bending vibrations of crystallization water molecules and N-H ones of the ammonium cation is considered in the context of different types of interactions with the closest neighbors in the structure.     

Crystal structure of Ba<Subscript>3</Subscript>[UO<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>(NCS)]<Subscript>2</Subscript> · 9H<Subscript>2</Subscript>O

Single crystals of Ba₃[UO₂(C₂O₄)₂(NCS)]₂ · 9H₂O are synthesized and studied by X-ray diffraction. The crystals are orthorhombic, space group Fddd, Z = 16, and the unit cell parameters are a = 16.253(3) Å, b = 22.245(3) Å, c = 39.031(6) Å. The main crystal structural units are mononuclear complex groups [UO₂(C₂O₄)₂NCS]^3? of the crystal-chemical family (AB ₂ ⁰¹ M¹ (A = UO ₂ ²⁺ , B⁰¹ = C₂O ₄ ^2? , M¹ = NCS^?) of the uranyl complexes linked into a three-dimensional framework by electrostatic interactions and hydrogen bonds involving oxalate ions and water molecules.     

<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.     

Exploring the Mechanism of Reactions of SiX<Subscript>3</Subscript> and CX<Subscript>3</Subscript> Radicals with Si<Subscript>20</Subscript>X<Subscript>20</Subscript> Fullerenes (X = H,F): A Density Functional Study

We have applied density functional calculations to study reactions SiX₃ + Si₂₀X₂₀, and CX₃ + Si₂₀X₂₀ (X = H, F) based on two reaction channels (H- or F-abstraction and H-or F-displacement from Si₂₀H₂₀ and Si₂₀F₂₀). Our results show that SiX₃ radicals prefer the hydrogen or halogen atom abstraction from Si₂₀H₂₀ and Si₂₀F₂₀ fullerenes. The exothermic reaction channels are proceed via reactant-like transition states i.e. the elongation of the breaking bonds of transition states is smaller than that of their forming bonds. Among the mentioned reaction channels, the reactions of SiF₃ radical with Si₂₀F₂₀ and CF₃ radical with Si₂₀H₂₀ are most favorable both thermodynamically and kinetically with the lowest barrier height exothermic character. Generally, the reactions of Si₂₀H₂₀ and Si₂₀F₂₀ with SiF₃ radical are more favorable than SiH₃ radical and the reaction of CH₃ and CF₃ radicals with Si₂₀H₂₀ fullerenes is more favorable than SiH₃ and SiF₃ radicals. These results are in agreement with the electrostatic surface potentials of reactants.     

Synthesis and structure of the complex [Mo<Subscript>3</Subscript>(μ<Subscript>3</Subscript>-S)(μ<Subscript>2</Subscript>-S<Subscript>2</Subscript>)<Subscript>3</Subscript>(Et<Subscript>2</Subscript>NCS<Subscript>2</Subscript>)<Subscript>3</Subscript>]I

The structure of tri-μ₂-disulfido-μ₃-thiotris(diethyldithiocarbamato)-S,S′-triangle-trimolybdenum iodide [Mo₃(μ₃-S)(μ₂-S₂)₃(Et₂NCS₂)₃]I was determined. The compound was characterized by differential thermal analysis and IR, Raman, and X-ray electronic spectroscopy.     

Solid solutions (Ru,Nb)Sr<Subscript>2</Subscript>(Sm<Subscript>1.4</Subscript>Ce<Subscript>0.6</Subscript>)Cu<Subscript>2</Subscript>O<Subscript>10−δ</Subscript>: Synthesis,structure, and properties

Solid solutions of as-batch composition (Ru_1?x Nb _x )Sr₂(Sm_1.4Ce_0.6)Cu₂O_10?δ (the Ru,Nb)-1222 phase), where x = 0.0, 0.25, 0.50, 0.75, or 1.00, have been synthesized and characterized by X-ray diffraction. A correlation is proposed between the refined composition of the Ru-1222 and Nb-1222 phases and their structural features. With increasing oxygen concentration in the Ru-1222 phase, the superconducting transition temperature increases from T _c = 28 to T _c = 34 K. The composition and magnetic properties of the Ru-1222 phase are affected by the batch composition: unlike in Ru + RuO₂ mixtures, the presence of ruthenium in the batch decreases the oxygen proportion and increases the magnetic ordering temperature T _m; the phase of as-batch composition NbSr₂(Sm_1.4Ce_0.6)Cu₂O_10?δ is paramagnetic.     

Concentration Space of Homogeneous Garnet in the System Ga<Subscript>2</Subscript>O<Subscript>3</Subscript>–(Y,Bi)<Subscript>3</Subscript>(Fe,Ga)<Subscript>5</Subscript>O<Subscript>12</Subscript>–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

The concentration space of homogeneous garnet in the system Ga₂O₃–(Y, Bi)₃(Fe, Ga)₅O₁₂–Fe₂O₃ was determined by X-ray powder diffraction analysis. The obtained results expand the knowledge of the possible variations of cation ratios Y : Bi : Fe : Ga in garnet, which can be used for searching for and creating new stable magneto-optical materials.     

Crystal structure of [(C<Subscript>6</Subscript>H<Subscript>5</Subscript>)<Subscript>4</Subscript>P][Ni(B<Subscript>9</Subscript>C<Subscript>2</Subscript>H<Subscript>11</Subscript>)<Subscript>2</Subscript>]·CCl<Subscript>4</Subscript>

A new compound containing the tetraphenylphosphonium cation and the nickel(III) bisdicarbollyl anion, [(C₆H₅)₄P][Ni(B₉C₂H₁₁)₂]·CCl₄, was synthesized and investigated by XRD at room temperature (295 K). Crystal data: C₂₉H₄₂B₁₈PCl₄Ni, M = 816.69, monoclinic, space group P2/c; unit cell parameters a = 13.5873(6) Å, b = 7.1475(2) Å, c = 20.7829(8) Å, β = 94.4595(13)°, V = 2012.2(2) ų, Z = 2, d _calc = 1.348 g/cm³. The structure was solved by direct and Fourier methods and refined by the full-matrix least squares method in an anisotropic (isotropic for H) approximation to the final R ₁ = 0.0466 for 3055 I _hkl ≥ 2σ _I of 23,655 reflections collected and 5618 independent I _hkl (Bruker X8 APEX diffractometer, λMoK _α).     

Crystal structure of Cs[(UO<Subscript>2</Subscript>)<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>2</Subscript>(OH)] · H<Subscript>2</Subscript>O

Single crystals of Cs[(UO₂)₂(C₂O₄)₂(OH)] · H₂O were synthesized and structurally studied using X-ray diffraction. The compound crystallizes in monoclinic space group P2₁/m, Z = 2, with the unit cell parameters a = 5.5032(4) Å, b = 13.5577(8) Å, c = 9.5859(8) Å, β = 97.012(3)°, V = 709.86(9) ų, R = 0.0444. The main building units of crystals are [(UO₂)₂(C₂O₄)₂(OH)]^? layers of the A₂K ₂ ⁰² M² (A = UO ₂ ²⁺ , K⁰² = C₂O ₄ ^2? , and M² = OH^?) crystal-chemical family. Uranium-containing layers are linked into a three-dimensional framework via electrostatic interactions with outer-sphere cations and hydrogen bonds with water molecules.     

High-temperature reactions in the Co<Subscript>3</Subscript>Cr<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>6</Subscript>–Cr(PO<Subscript>3</Subscript>)<Subscript>3</Subscript> system

A new dichromium(III) cobalt(II) diphosphate(V) of the formula CoCr₂(P₂O₇)₂ was detected in the Co₃Cr₄(PO₄)₆–Cr(PO₃)₃ system. The new compound was obtained as a result of high-temperature solid-state reactions between CoCO₃, Cr₂O₃ and (NH₄)₂HPO₄ as well as between Cr(PO₃)₃ and Co₃Cr₄(PO₄)₆. CoCr₂(P₂O₇)₂ was characterized using XRD, DTA and IR methods. Results demonstrated that CoCr₂(P₂O₇)₂ crystallizes in the triclinic system and its unit cell parameters were calculated. Its infrared spectrum was presented. CoCr₂(P₂O₇)₂ melts incongruently at 1270±10 °C with a formation of solid α-CrPO₄. The compound Co₃Cr₄(PO₄)₆, component of the system under study, was obtained for the first time as a pure phase. Its thermal stability was also investigated. Co₃Cr₄(PO₄)₆ is stable in air up to 1410 ± 20 °C.     

Application of a modified Pechini method for the synthesis of Ln<Subscript>2</Subscript>MGe<Subscript>4</Subscript>O<Subscript>12</Subscript> (Ln = Y,Eu; M = Ca,Zn, Mn) optical hosts

A modified Pechini method followed by conventional and microwave heating was used to synthesise the new promising Ln₂MGe₄O₁₂ (Ln = Y, Eu; M = Ca, Zn, Mn) optical hosts. Comparison between solid-state and Pechini synthesis methods showed that the latter reduces the temperature required for cyclo-tetragermanate formation. The highest yield of cyclo-tetragermanates for both methods is observed at 1,000–1,100 °C, with significantly shorter time of annealing in the case of the Pechini synthesis. Compositional, structural and morphological characterisations of the samples obtained by both routes were carried out using X-Ray powder diffraction, thermogravimetry, electron spin resonance spectroscopy, energy-dispersive X-Ray spectroscopy and scanning electron microscopy.