The series of titanium (IV) complexes trans-[TiCl4(OPPh3)(2)] (1), trans-[TiBr4(OPPh3)(2)] (2) and trans[TiI4(OPPh3)(2)] (3) were obtained as polycrystalline powders by heating the corresponding metal tetrahalides with triphenylphosphine oxide in evacuated sealed glass ampoules. The crystal structures were determined by single crystal X-ray diffraction. Compounds 1 and 2 were isolated as yellow and brown crystalline powders, with yields 70 and 75%, respectively. This paper discusses the synthesis of these coordination compounds 1-3 and their crystal structures, and analyzes the geometric parameters of the related molecular complexes of niobium and rhenium for use in the design of magnetically diluted systems.

Using XPS and DFT, we have studied a series of octahedral rhenium cluster compounds: ternary thiobromides Re6S4+nBr10-2n, n = 0, 1, 3, 4 and alkali metal salts of anionic complexes [Re6S4+nBr10-n]n-, n = 1-4. These two series contain [Re6S4+nBr4-n] cluster cores, which are the building blocks of both discrete complexes and polymeric compounds, and have the same coordination polyhedron of rhenium atoms. The constancy of the coordination polyhedron of Re reduces the effect of structural differences and allows to study the change in the electronic state of the rhenium atoms of the Re6 metallocluster with increasing number of less electronegative (compared to bromine) sulfur atoms in the cluster core. This change results in the decrease in the binding energy (BE) Re 4f7/2 in the series of anionic complexes [Re6S4+nBr10-n]n-. A similar dependence is observed in the series of ternary thiobromides. Re6S8Br2 falls out of this trend, which is explained by a change in the type of binding of the cluster cores. The BE S 2p3/2 of the sulfide ligands and the BE Br 3d5/2 of the bromide ligands decrease as the number of sulfur atoms in the cluster core and the charge of anionic complexes increases. The difference in BE values for the inner Bri and apical Bra bromide ligands shows that the inner ligands are more covalent and the apical ligands are more ionic. Calculated energies of the Re 4f, S 2p, Br 3d orbitals confirm the general tendency for the energy to decrease as the number of sulfur atoms in the cluster cores increases. Calculation of the atom charges for discrete complexes [Re6S4+nBr10-n]n-, showed that with increasing number of sulfur atoms in the cluster cores, the negative charge of the ligands increases, while the charge of the rhenium atoms remains unchanged. This suggests that the chemical shift of the Re4f binding energy is determined by the potentials of the surrounding atoms (Madelung potential) and that the chemical shift of the ligands depends on the charge of the atom.

A series of rhenium compounds with the octahedral cluster core {Re6S8-xBrx} (x = 0–4): with molecular and polymeric structure were obtained. In these compounds the cluster core composition varies monotonically, the geometry of the cluster and the rhenium coordination polyhedron are retained unchanged, while the symmetry of the cluster changes. The vibrational spectra (Raman and IR) were recorded and analyzed for compounds with all possible S/Br ratios in the cluster core. The group vibrations of clusters were attributed with the use of DFT calculations of vibrational spectra. It is shown that the set of main characteristic bands is retained in both ionic and polymeric compounds regardless of the composition and the symmetry of the cluster core while the observed vibration frequencies of these bands depend on the S/Br ratio in the cluster core. In particular, the group Re–S stretching vibrations (A1g(S8) and T2g(S8) modes) shifted to higher frequencies with the increase in the number of Br atoms in the cluster. The difference in the connectivity in polymeric compounds leads to an increase in the number of bands in the spectra and to the disappearance of the A1g(Br) modes.

The binary niobium sulfide NbS4 was synthesized as a crystalline phase. We showed that NbS4 can be formed from Nb metal, from defect niobium sulfide Nb1.14S2, or from some other niobium dichalcogenides in reactions with excess sulfur in an evacuated ampule at 440 °C. The crystal structure of NbS4 (monoclinic space group C2/c, a = 13.126(2) Å, b = 10.454(1) Å, c = 6.951(1) Å, β = 111.939(5)°) is a packing of infinite chains {NbS4}1∞, analogous to VS4. In the chains, Nb atoms are in a tetragonal-antiprismatic coordination of sulfur atoms of disulfide groups (S2)2-; short Nb···Nb contacts (2.896 Å) alternating with longer ones (3.278 Å) appear within the chains at 150 K. According to density functional theory calculations, NbS4 is a thermodynamically stable compound, a nonmagnetic semiconductor. NbS4 is a new member of the family of quazi-one-dimensional compounds, group 5 metal polychalcogenides, well-known for their interesting electrophysical properties. The synthesis and crystal structure as well as the thermal stability and lattice dynamics of NbS4 are discussed here.

Данный обзор направлен на обобщение строения, электронных свойств, а также функциональных свойств халькогенидов ранних переходных металлов (ХРПМ) 4—7 групп (M = Ti, Zr, Hf, V, Nb, Ta, Mo, W, Re). Рассматривается строение различных халькогенидов, получение наноматериалов на их основе, влияние электронных свойств металлов и халькогенов на структурные и функциональные особенности халькогенидов металлов. Обсуждаются природа полимеризации в ХРПМ, окислительно-восстановительные свойства халькогенов.

This review is aimed at the generalization of structures, electronic and functional properties of early transition metal (Groups 4-7) chalcogenides (ETMCs) ( M = Ti, Zr, Hf, V, Nb, Ta, Mo, W, Re). The structures of various chalcogenides, the preparation of nanomaterials based on them, the effect of the electronic properties of metals and chalcogens on the structural and functional features of metal chalcogenides are considered. The nature of polymerization in ETMCs and redox properties of chalcogens are discussed.

New O-centered tetranuclear titanium complex Ti4O(Se-2)(4)Br-6 has been prepared from TiSe1.73, Se, SeO2 and Br-2 at moderate temperature by ampule synthesis. Its X-ray crystal structure (monoclinic space group P2(1)/c, a=9.4850(2), b=11.4667(2), c=19.1413(5)angstrom, beta=92.0080(10)degrees, Z=4, V=2080.56(8)angstrom(3)) includes molecular complex Ti4O(Se-2)(4)Br-6 based on fragment {Ti-4(mu(4)-O)} coordinated by diselenide (Se-2)(2-) and bromide bridging ligands. Ti4O(Se-2)(4)Br-6 is a new member of family of O-centered tetranuclear complexes with the fragment {M-4(mu(4)-O)(Q(2))(4)} (M=Ti, Nb, Ta; Q=S, Se, Te); here we discuss its synthetic features, crystal and electronic structure.

The first vanadium selenoiodide V4O(Se2)4I6·I2 was synthesized at a moderate temperature of 220 °C from V, Se, I2, and water. Its crystal structure (tetragonal space group P42/nbc, a = 11.838(1) Å, c = 18.689(1) Å) contains O-centered vanadium(IV) tetranuclear fragment [V4(μ4-O)(μ2-Se2)4(μ2-I)2I4], where the edges of the distorted tetrahedron V4 are bridged by four diselenide (Se2)2- and two iodide ligands; four terminal iodides coordinate V atoms additionally. This type of complex is known for Ti, Nb, and Ta but is new for vanadium. Magnetic susceptibility measurements of V4O(Se2)4I6·I2 showed four unpaired electrons on vanadium atoms at room temperature and drop of the effective magnetic moment at cool down, presumably due to partial electron pairing. Probability of this transition to the diamagnetic state is in accord with the calculated electronic structure.

Sulfur-rich transition metal polysulfides with multiple disulfide bonds (S-S) are a family of inorganic materials with unusual chemical properties and potential in catalysis and energy-related applications. In the current work, we present a kinetic study of the thermal decomposition of amorphous pentasulfides MoS5 and WS5 based on thermogravimetric analysis (TGA) in an inert atmosphere at various heating rates (10, 20, 30 degrees C/min). Thermal decomposition of both pentasulfides proceeds via a two-step, consecutive process. First, starting from similar to 190 degrees C (M = Mo) or similar to 240 degrees C (M = W) MS5 transform into intermediate products MS3, which then convert into MS2 at similar to 380 degrees C (M = Mo) or 300 degrees C (M = W) (at the heating rate of 30 degrees C/min). The main kinetic parameters (activation energy, pre-exponential factor and reaction type) were calculated. Both steps are well described by the Avrami-Erofeev model, comprising random nucleation and subsequent nucleate growth. The rate-controlling step is diffusion, as spherical particle morphology of MoS5 and WS5 may slow down the elimination of sulfur produced during decomposition. The final decomposition products are weakly crystalline disulfides (MoS2, WS2), which inherit the spherical morphology of MoS5 (WS5). Theoretical calculations suggest that the very first step of the MS5 decomposition process is the depolymerization of MS5 chains into cluster fragments, rather than direct desulfurization. (C) 2020 Elsevier B.V. All rights reserved.

Two crystal modifications of new molecular niobium(IV) complex trans-NbI4(OPPh3)(2) were obtained by ampoule synthesis, and their X-ray crystal structures were solved (P-1, a = 9.5795 angstrom, b = 9.7287 angstrom, c = 11.2337 angstrom, alpha = 107.984 degrees, beta = 104.061 degrees, gamma = 95.500 degrees, V = 949.24 angstrom(3); P2(1), a = 10.204 angstrom, b = 16.039 angstrom, c = 11.857 angstrom, beta = 102.663 degrees, V = 1893.3 angstrom(3)). For the series of molecular complexes trans-NbX4(OPPh3)(2) (X = Cl, Br, I) magnetic properties were studied and systematized using EPR, magnetic susceptibility measurements, and theory calculations with DFT approximation. Theory calculations of EPR parameters have shown good accordance with experimental data and allowed to establish a negative sign of the principal hyperfine tensor values.

Amorphous pentasulfides MoS5 and WS5 were studied in a series of chemical reactions for the first time. Interaction of MoS5 and WS5 with melt of tetramethylthiuramdisulfide resulted in two new molecular complexes, [{Mo3S7}(dtC)(3)](S3H) and [{W3S4}(dtc)(4)(Me2NCHS)]. Halogenation of MoS5 and WS5 resulted in cluster coordination polymers M(3)S(7)Hal(4) (M = Mo, W; Hal = Cl, Br).

Combined experimental and computational investigation shows that the exclusively amorphous nature of MoS5 and WS5 is related to flexible chains in their structures, akin to traditional polymers, making these materials remarkably different from most of the other transition metal chalcogenides that may be obtained in crystalline state. The presented findings are important for both fundamental understanding of possible formation processes of new materials and for promoting their practical uses, as shown on the example of Li-ion batteries. More information can be found in the Full Paper by Sofya B. Artemkina, Andrey N. Enyashin, Ekaterina D. Grayfer et al. on page 1488 in Issue 12, 2019 (DOI: 10.1002/cnma.201900526).

A series of ZrS3 samples have been synthesized from elements at temperatures from 350 to 650°C. Stable ZrS3 colloid dispersions in different organic media (acetonitrile, dimethylformamide, ethanol, and isopropanol) were obtained from the polycrystalline samples. The structural and spectroscopic identities of the ZrS3 particles were confirmed by X-ray powder diffraction and Raman spectra. The sizes and morphology of particles in the colloid dispersions have been studied by transmission electron microscopy and dynamic light scattering method; the concentrations of the dispersions were found to depend on condition of synthesis of the initial bulk ZrS3.

New molecular niobium(IV) complexes NbCl4(OPPh3)2(1) and NbBr4(OPPh3)2(2) are synthesized by heating respective niobium pentahalide with a mixture of triphenylphosphine and triphenylphosphine oxide. For the obtained compounds the crystal structure is solved: 1P-1, a = 13.3540(5) Å, b = 9.4461(3) Å, c = 9.5635(3) Å, α = 93.084(1)°, β = 121.263(1)°, γ = 115.058(1)°, Z = 1, R1 = 0.0194; 2P-1, a = 13.308(2) Å, b = 9.5934(8) Å, c = 9.5556(9) Å, α = 93.975(3),°, β = 119.391(4)°, γ = 114.740(4)°, Z = 1, R1 = 0.0184. The unpaired electron is mainly located on the niobium atom, which is supported by quantum chemical calculations and EPR spectroscopic results.

Новые молекулярные комплексы ниобия(IV) NbCl4(OPPh3)2 (1) и NbBr4(OPPh3)2 (2) получены нагреванием соответствующего пентагалогенида ниобия со смесью трифенилфосфина и трифенилфосфин оксида. Для полученных соединений решена кристаллическая структура (1: P-1, a = 13.3540(5), b = 9.4461(3), c = 9.5635(3) Å, α = 93.084(1), β = 121.263(1), γ = 115.058(1)°, Z = 1, R1 = 0.0194; 2: P-1 a = 13.308(2), b = 9.5934(8), c = 9.5556(9) Å, α = 93.975(3), β = 119.391(4), γ = 114.740(4)°, Z = 1, R1 = 0.0184). Неспаренный электрон локализован преимущественно на атоме ниобия, что подтверждается квантово-химическими расчетами и результатами ЭПР спектроскопии.