77Se NMR spectroscopic, DFT MO, and VBT investigations of the reversible dissociation of solid (Se6I2)[AsF6]2.2SO2 in Liquid SO2 to solutions containing 1,4-Se6I2(2+) in equilibrium with Se(n)2+ (n = 4, 8, 10) and seven binary selenium iodine cations: preliminary evidence for 1,1,4,4-Se4Br4(2+) and cyclo-Se7Br+.

The composition of a complex equilibrium mixture formed upon dissolution of (Se(6)I(2))[AsF(6)](2).2SO(2) in SO(2)(l) was studied by (77)Se NMR spectroscopy at -70 degrees C with both natural-abundance and enriched (77)Se-isotope samples (enrichment 92%). Both the natural-abundance and enriched NMR spectra showed the presence of previously known cations 1,4-Se(6)I(2)(2+), SeI(3)(+), 1,1,4,4-Se(4)I(4)(2+), Se(10)(2+), Se(8)(2+), and Se(4)(2+).

1,1,4,4-Tetra-methyl-piperazinediium dibromide.

A small quantity of the title compound, C(8)H(20)N(2) (2+)·2Br(-), was formed as a by-product in a reaction between a diamine and an alkyl bromide. The asymmetric unit contains half of a centrosymmetric dication and a bromide anion. In the crystal, weak inter-molecular C-H⋯Br hydrogen bonds consolidate the crystal packing.

Thermal and spectroscopic investigation of europium and samarium sulphates hydrates by TG-FTIR and ICP-MS techniques.

The investigation of europium(III) sulphate hydrate and samarium(III) sulphate hydrate was performed by thermal analysis (TG-DTG) and simultaneous infrared evolved gas analysis-Fourier transformed infrared (EGA-FTIR) spectroscopy. The TG, DTG and DTA curves were recorded at the 25-1400 degrees C in the dynamic air atmosphere by TG/DTA analyser. The infrared evolved gas analysis was obtained on the FTIR spectrometer.

N,N-Dimethyl-N-propyl-propan-1-aminium chloride monohydrate.

The title compound, C(8)H(20)N(+)·Cl(-)·H(2)O, has been prepared by a simple one-pot synthesis route followed by anion exchange using resin. In the crystal structure, the cations are packed in such a way that channels exist parallel to the b axis. These channels are filled by the anions and water mol-ecules, which inter-act via O-H⋯Cl hydrogen bonds [O⋯Cl = 3.

Accounting for the differences in the structures and relative energies of the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I4 2+, the Se-I pi-bonded Se2I4 2+, and their higher-energy isomers by AIM, MO, NBO, and VB methodologies.

The bonding in the highly homoatomic np pi-np pi (n > or = 3)-bonded S2I42+ (three sigma + two pi bonds), the Se-I pi-bonded Se2I42+ (four sigma + one pi bonds), and their higher-energy isomers have been studied using modern DFT and ab initio calculations and theoretical analysis methods: atoms in molecules (AIM), molecular orbital (MO), natural bond orbital (NBO), and valence bond (VB) analyses, giving their relative energies, theoretical bond orders, and atomic charges. The aim of this work was to seek theory-based answers to four main questions: (1) Are the previously proposed simple pi*-pi* bonding models valid for S2I42+ and Se2I42+? (2) What accounts for the difference in the structures of S2I42+ and Se2I42+? (3) Why are the classically bonded isolobal P2I4 and As2I4 structures not adopted? (4) Is the high experimentally observed S-S bond order supported by theoretical bond orders, and how does it relate to high bond orders between other heavier main group elements? The AIM analysis confirmed the high bond orders and established that the weak bonds observed in S2I42+ and Se2I42+ are real and the bonding in these cations is covalent in nature. The full MO analysis confirmed that S2I42+ contains three sigma and two pi bonds, that the positive charge is essentially equally distributed over all atoms, that the bonding between S2 and two I2+ units in S2I42+ is best described by two mutually perpendicular 4c2e pi*-pi* bonds, and that in Se2I42+, two SeI2+ moieties are joined by a 6c2e pi*-pi* bond, both in agreement with previously suggested models.

Electronic structures and molecular properties of chalcogen nitrides Se2N2 and SeSN2.

The electronic structures and molecular properties of S2N2 as well as the currently unknown chalcogen nitrides Se2N2 and SeSN2 have been studied using various ab initio and density functional methods. All molecules share a qualitatively similar electronic structure and can be primarily described as 2pi-electron aromatics having minor singlet diradical character of 6-8% that can be attributed solely to the nitrogen atoms. This diradical character is manifested in the prediction of their molecular properties, in which coupled cluster and multiconfigurational approaches, as well as density functional methods, show the best performance.

A computational and experimental study of the structures and Raman and 77Se NMR spectra of SeX3+ and SeX2 (X = Cl, Br, I): FT-Raman spectrum of (SeI3)[AsF6].

The ability of MP2, B3PW91 and PBE0 methods to produce reliable predictions in structural and spectroscopic properties of small selenium-halogen molecules and cations has been demonstrated by using 6-311G(d) and cc-pVTZ basis sets. Optimized structures and vibrational frequencies agree closely with the experimental information, where available. Raman intensities are also well reproduced at all levels of theory.

Experimental and theoretical investigations of tellurium(IV) diimides and imidotelluroxanes: X-ray structures of B(C6F5)3 adducts of OTe(mu-NtBu)2TeNtBu, [OTe(mu-NtBu)2Te(mu-O)]2 and tBuNH2.

The hydrolysis of (t)BuNTe(mu-N(t)Bu)(2)TeN(t)Bu (1) with 1 or 2 equiv of (C(6)F(5))(3)B.H(2)O results in the successive replacement of terminal imido groups by oxo ligands to give the telluroxane-Lewis acid adducts (C(6)F(5))(3)B.OTe(mu-N(t)Bu)(2)TeN(t)Bu (2) and [(C(6)F(5))(3)B.

Ca[Ag2(SCN)4].2H2O.

Calcium tetrathiocyanatodiargentate(I) dihydrate, Ca[Ag(2)(SCN)(4)].2H(2)O, contains eight-membered Ag(4)S(4) rings bonded together through shared atoms to form layers parallel to (100). The thiocyanate groups link the layers to Ca-O chains running parallel to the c axis.

Experimental and theoretical investigations of structural trends for selenium(IV) imides and oxides: X-ray structure of Se3(NAd)2.

The thermal decomposition of Se(NAd)(2) (Ad = 1-adamantyl) in THF was monitored by (77)Se NMR and shown to give the novel cyclic selenium imide Se(3)(NAd)(2) as one of the products. An X-ray structural determination showed that Se(3)(NAd)(2) is a puckered five-membered ring with d(Se-Se) = 2.404(1) A and |d(Se-N)| = 1.

Conformations and energetics of sulfur and selenium diimides.

The geometries and energetics of different conformations of sulfur and selenium diimides E(NR)(2) (E = S, Se; R = H, Me, (t)Bu, C(6)H(3)Me(2)-2,6, SiMe(3)) have been studied by using various ab initio and DFT molecular orbital techniques. The syn,syn conformation is found to be most stable for parent E(NH)(2), but in general, the preferred molecular conformation for substituted chalcogen diimides is syn,anti. In the case of E(NH)(2) the present calculations further confirm that syn,syn and syn,anti conformations lie energetically close to each other.

Polymorphism in Cs[AgZn(NCS)4].

The title compound, caesium silver zinc tetrathiocyanate, crystallizes in two polymorphic forms, in space groups P2(1)/n and C2/c. Both structures form a continuous three-dimensional network. The structure in C2/c contains a delocalized Ag atom in a binuclear-like anion, where two [Ag(NCS)(4)] units (delocalized Ag as an average) share two common NCS(-) ligands.

Cs[Ag4Zn2(SCN)9].

Caesium tetrasilver dizinc nonathiocyanate, Cs[Ag(4)Zn(2)(SCN)(9)], forms a continuous structure, where the Ag atoms and the S atoms of the thiocyanate groups form chains which run along [101]. These chains are bonded together through the Cs and Zn atoms. It is not possible to distinguish between space groups P1 and P-1, but, if the latter space group is correct, the structure contains a thiocyanate group disordered across a centre of inversion.

Preparation and structural characterization of (Me(3)SiNSN)(2)Se, a new synthon for sulfur-selenium nitrides.

The reaction of (Me(3)SiN)(2)S with SeCl(2) (2:1 ratio) in CH(2)Cl(2) at -70 degrees C provides a route to the novel mixed selenium-sulfur-nitrogen compound (Me(3)SiNSN)(2)Se (1). Crystals of 1 are monoclinic and belong the space group P2(1)/c, with a = 7.236(1) A, b = 19.

Calcium dicaesium silver thiocyanate dihydrate.

The title compound, CaCs2[Ag2(SCN)6]*2H2O, forms a continuous structure where the Ag atoms form chains with S atoms in the c-axis direction. The chains are bonded together through Cs and Ca atoms. The crystal water of the structure is bonded to the Ca atoms, which lie on centers of symmetry.

Dicaesium silver zinc thiocyanate, Cs2[AgZn(SCN)5].

The title compound, dicaesium(I)-mu-thiocyanato-kappa2N:S-zinc(II)-tetra-mu-thiocyanato-kappa2S:N-argentate(I), crystallizes in the orthorhombic space group Pmn2(1) and contains units of composition AgZn(SCN)3 lying on a mirror plane and bonded together through Cs+ ions and thiocyanate groups. The crystal studied contained equal numbers of inversion twins.

Alkoxo Bound Monooxo- and Dioxovanadium(V) Complexes: Synthesis, Characterization, X-ray Crystal Structures, and Solution Reactivity Studies.

A large variety of oxovanadium(V) complexes, mononuclear VO(2)(+) and VO(3+) in addition to the dinuclear VO(3+), of the structural type (VOL)(2), (VOHL)(2), VOLHQ, K(VO(2)HL), K(VO(2)H(2)L), or (salampr) (VO(2)L) {where L = Schiff base ligand possessing alkoxo group(s); HQ = 8-hydroxyquinoline; salampr = cation of reduced Schiff base derived from salicylaldehyde and 2-amino-2-methylpropan-1-ol}, bound to alkoxo, phenolate and imine groups have been synthesized in high yields and characterized by several spectral and analytical methods, including single crystal X-ray studies. While the mononuclear VO(2)(+) complexes have been synthesized at alkaline pH, the dinuclear VO(3+) complexes have been synthesized under neutral conditions using alkoxo rich Schiff base ligands. The X-ray structures indicate that the cis-dioxo complexes showed longer V-O(alkoxo) bond lengths compared to the monooxo counterparts.