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The reaction of [(Me3Si)2N]2S with equimolar amounts of SCl2 and S2Cl2 produces S4N2 in a good yield. The reaction of [(Me3Si)2N]2S with a 3:1:1 mixture of S2Cl2, Se2Cl2, and SeCl4 yields a dark brown-red insoluble material that was inferred to be mainly SSeSNSN on the basis of the elemental analysis, mass spectroscopy, vibrational analysis, and NMR spectroscopy. Attempts to prepare selenium-rich species resulted in the formation of elemental selenium or Se3N2Cl2. The experimental work was supported by ab initio MO calculations which establish the structural and stability relationships of the different members of the series 1,3-SexS4-xN2 (x = 0-4). Full geometry optimization was carried out for each molecular species using the polarized split-valence MIDI-4* basis sets. The effects of electron correlation were taken into account involving the second-order M?1er-Plessett perturbation theory. Each molecule was found to lie in an approximate half-chair conformation that is well established for 1,3-S4N2 (i.e., interacting planar NEN and EEE fragments; E = S, Se). The bond parameters agree well with experimental information where available. Whereas the lengths of the bonds in the NEEEN fragment approach those of the single bonds, the bonds in the NEN fragment show marked double bond character. The stabilities of the molecules decrease expectedly with increasing selenium content as judged by the total binding energy at the MP2 level of theory. Within a given chemical composition, isomers containing a N=Se=N unit lie higher in energy than those containing a N=S=N unit. These results may explain why selenium-rich SexS4-xN2 molecules have not been isolated.

The crystallization of a new allotrope of cyclo-octaselenium, named γ-monoclinic selenium, from a solution of dipiperidinotetraselane in carbon disulphide is described.The allotrope γ-Se8 crystallizes in space group P21/c (no. 14) with a=15.018(1), b=14.713(1), c=8.789(1) Angstroem, β=93.61(1) deg, and Z=64 (atoms).The crystal structure has been determined by X-ray diffraction from Mo-Kα diffractometer data and refined to R 0.047 for 2 525 observed reflections.There are two crown-shaped Se8 rings in the asymmetric unit, with bond lengths, bond angles , and dihedral angles in the ranges 2.326(3)-2.344(3) Angstroem, 103.3(1)-109.1(1) deg, and 96.5-107.2 deg respectively.The overall averages, 2.334+/-0.005 Angstroem, 105.8+/-1.4 deg, and 101.1+/-2.2 deg, are the same, within error limits, as in α- and β-monoclinic selenium.There are more short contacts between the rings than in the α and β forms, the shortest ones being 3.346(3) and 3.404(3) Angstroem.

Selenium clusters are doped with sodium atoms in the reaction zone of a dual laser vaporization source. Product clusters SeN and Na 2SeN with N=4-8 are deposited in a nitrogen matrix and investigated by Raman spectroscopy. Beside the Raman band of pure Se N clusters, a new intense band between 165 and 225 cm-1 is observed. Within a simple model of dynamical charge transfer the new band is attributed to certain vibrational modes with considerable changes of Na-Se bond lengths. The assignment is confirmed by density functional calculations. A bonding model for the Na2SeN clusters containing horseshoe shaped polyanionic selenium chains is developed.

The introduction of (N2)3-? radicals into multinuclear lanthanide molecular magnets raised hysteresis temperatures by stimulating strong exchange coupling between spin centers. Radical ligands with larger donor atoms could promote more efficient magnetic coupling between lanthanides to provide superior magnetic properties. Here, we show that heavy chalcogens (S, Se, Te) are primed to fulfill these criteria. The moderately reducing Sm(II) complex, [Sm(N??)2], where N?? is the bulky bis(triisopropylsilyl)amide ligand, can be oxidized (i) by diphenyldichalcogenides E2Ph2 (E = S, Se, Te) to form the mononuclear series [Sm(N??)2(EPh)] (E = S, 1-S; Se, 1-Se, Te, 1-Te); (ii) S8 or Se8 to give dinuclear [{Sm(N??)2}2(μ-η2:η2-E2)] (E = S, 2-S2; Se, 2-Se2); or (iii) with Te=PEt3 to yield [{Sm(N??)2}(μ-Te)] (3). These complexes have been characterized by single crystal X-ray diffraction, multinuclear NMR, FTIR, and electronic spectroscopy; the steric bulk of N?? dictates the formation of mononuclear complexes with chalcogenate ligands and dinuclear species with the chalcogenides. The Lα1 fluorescence-detected X-ray absorption spectra at the Sm L3-edge yielded resolved pre-edge and white-line peaks for 1-S and 2-E2, which served to calibrate our computational protocol in the successful reproduction of the spectral features. This method was employed to elucidate the ground state electronic structures for proposed oxidized and reduced variants of 2-E2. Reactivity is ligand-based, forming species with bridging superchalcogenide (E2)-? and subchalcogenide (E2)3-? radical ligands. The extraordinarily large exchange couplings provided by these dichalcogenide radicals reveal their suitability as potential successors to the benchmark (N2)3-? complexes in molecular magnets.

Aromatic and heteroaromatic diazonium salts were efficiently converted into the corresponding trifluoromethylthio- or selenoethers by reaction with Me4NSCF3 or Me4NSeCF3, respectively, in the presence of catalytic amounts of copper thiocyanate. These Sandmeyer-type reactions proceed within one hour at room temperature, are applicable to a wide range of functionalized molecules, and can optionally be combined with the diazotizations into one-pot protocols.

The reaction of [(Me3Si)2N]2S with equimolar amounts of SCl2 and SO2Cl2 produces S4N4 in a good yield. The new chalcogen nitride 1,5-Se2S2N4 hasbeen prepared in high yield by two different reactions: (a) from [(Me3S i)2N]2S and SeCl4 and (b) from [(Me3Si)2N]2Se with equimolar amounts of SCl2 and SO2Cl2. 1,5-Se2S2N4 has a cage structure similar to those of S4N4 and Se4N4. The crystal structure is disordered with site occupation factors ca. 50% for selenium in each chalcogen atom position. The 12 eV EI mass spectrum shows Se2SN2(+) as the fragment with highest mass. Both the (14)N and (77)Se NMR spectra show a single resonance (-238 and 1418 ppm, respectively). These data rule out the possibility that the crystalline sample is a solid solution of S4N4 and Se4N4 and imply the presenceof 1,5-Se2S2N4. This deduction was further verified by Raman spectrosco py and vibrational analysis.

A simple and efficient synthesis of solutions of pure SeCl2 in THF or dioxane (ca. 0.4 M) at 23 °C was achieved by treatment of elemental selenium with an equimolar amount of SO2Cl2. SeCl2 was characterized by 77Se NMR and Raman spectra. SeCl2 forms 1:1 or 1:2 adducts with tetramethylthiourea (tmtu) or tetrahydrothiophene (tht), respectively. The crystal structure of SeCl2·tmtu (1) reveals a T-shaped geometry [d(Se-Cl) = 2.443(4) A] with weak intramolecular Se-Cl interactions [d(Se-Cl) = 3.276(4) A]. Crystals of 1 are triclinic, space group P1, with a = 8.473(3) A, b = 9.236(3) A, c = 7.709(4) A, α = 109.90(3)°, β= 92.26(4)°, γ = 107.89(3)°, V = 532.9(4) A 3, and Z =2. The complex SeCl2(tht)2 (2) adopts a square planar geometry with d(Se-Cl) = 2.4149-(8) A. Crystals of 2 are monoclinic, space group C2/c, with a - 15.6784(8) A, b = 9.1678(4) A, c = 9.1246(4) A, β= 110.892(2)°, V = 1225.3(1) A,3 and Z = 4. The reaction of Ph3PS with SeCl2 gives Ph3PCl2 and a complex mixture of selenium Sulfides SenS8-n (n = 1-5), which were identified by 77Se NMR. Halogen exchange between SeCl2 and Me3SiBr in THF yields thermally unstable SeBr2 (ca. 0.4 M) characterized by 77Se NMR and Raman spectra.

The reaction of NaSeH and CpRu(PPh3)2Cl gave CpRu(PPh3)2SeH, while the synthesis of (MeCp)Ru(PPh3)2SeH required the use of NMe4SeH. The corresponding H2Se complexes could not be prepared, as CpRu(PPh3)2OTf failed to add H2Se and protonation of (MeCp)Ru(PPh3)2SeH gave (MeCp)Ru(PPh3)2H2+. The reaction of CpRu(PPh3)2OTf with elemental selenium gave [CpRu(PPh3)2]2(μ-η 1,η1-Se2)(OTf)2 (1). The compound 1·PhMe·CH2Cl2 crystallized in the monoclinic space group P21, with a = 15.965 (3) A?, b = 15.898 (5) A?, c = 18.406 (4) A?, α = γ = 90°, β = 111.28 (2)°, V = 4353 (3) A?3, and Z = 2. The structure was refined to R = 0.054 (Rw = 0.061). The crystallographic studies provide evidence for Ru-Se multiple bonding but show that the Ru2Se2 core is not planar, unlike the core of the analogous persulfido complex. Solutions of 1 reacted further with selenium to give primarily [CpRu(PPh3)]2(μ-η1,η 2-Se2)2(OTf)2. The analogous MeCp complex (2) was characterized by X-ray crystallography. It crystallizes in the triclinic space group P1, with a = 10.909 (5) A?, b = 13.530 (5) A?, c = 10.064 (4) A?, α = 110.13 (3)°, β = 112.18 (3)°, γ = 79.62 (3)°, V = 1289 (2) A3, and Z = 1. The structure was refined to R = 0.050 (Rw = 0.058). Compound 2 was reduced by Cp2Co to give the unstable compound [(MeCp)Ru(PPh3)]2(μ-η1,η 1-Se2)2, which could be reoxidized to give 2 and which in turn thermally eliminated SePPh3 to give (MeCp)4Ru4Se4.

The self-assembly method has been used to prepare a wide range of new adamantane-like anions of the type (2-) (M = Zn or Cd; R = alkyl or benzyl; X = Cl, Br, or I) as their Et4N(1+) salts.Metal (111or113Cd) NMR data have been measured for the cadmium complexes, and also for many of the possible mixed-metal complexes 4-n>(2-).In the complexes with mixed metals, the effects of Zn substitution on the metal chemical shifts are generally larger for the alkyl- and benzyl-thiolate complexes than for related benzenethiolate complexes.However, for i)6(CdX)n(CdX')4-n>(2-) (X/X'= Cl/Br, Cl/I, or Br/I), substituent effects are no larger than found in some PhS(1-)-bridged complexes.The reaction of i)6(CdX)4>(2-) (X = Cl, Br, or I) with E'8 (E' = S or Se) in CH2Cl2 gives i)12(CdX)4>(2-) as the major species detectable by metal, 13C, and, where applicable, 77Se NMR.However, the reaction does not occur stoichiometrically.The compound (Et4N)2i)6(CdBr)4> crystallizes in the monoclinic space group P 21/c with cell dimensions a = 24.079(3) Angstroem, b = 11.365(2) Angstroem, c = 22.561(3) Angstroem, β = 113.89(1), and Z = 4.The structure was refined to R(Rw) = 0.0663(0.0703) with the use of 2669 unique data with I > 2.5 ?(I).The anion contains an adamantane-type (μ2-S)6Cd4 cage composed of a nearly regular Cd4 tetrahedron and a distorted S6 octahedron, the irregularity of which is caused by 1,3-interactions of the substituent groups on the sulfur atoms.The axial or equatorial dispositions of the six alkyl groups in the four fused M3S3 rings are .For the zinc-group elements, this is the first example of an adamantane-like (μ-Salkyl)6M4 cage that has been characterized crystallographically.Key words: cadmium complex, cadmium-111/113 NMR, thiolate complex, X-ray analysis, zinc complex.

A series of six sulfur-selenium mixtures containing 0.4, 5, 15, 25, 35, and 45 molpercent of selenium were heated in evacuated ampoules at 430 deg C for 4 h and, keeping the material molten at 135 deg C, their natural-abundance 77Se NMR spectra were recorded.The equilibrium melt in each case was found to contain both heterocyclic SenS8-n species and polymeric material.The most abundant eight-membered selenium sulfide rings were SeS7, which was the main cyclic component in all melts studied in this work, and 1,2-Se2S6, the quantity of which increased with increasing selenium content of the melt.In addition the melts contained smaller amounts of 1,3, 1,4, and 1,5 isomers of Se2S6, 1,2,3, 1,2,4, and 1,2,5 isomers of Se3S5, 1,2,3,4, 1,2,3,5, and 1,2,5,6 isomers of Se4S4, 1,2,3,4,5-Se5S3, 1,2,3,4,5,6-Se6S2, and Se8.The relative distribution of the cyclic products as a function of the selenium content in the melt was virtually identical with that obtained earlier in the CS2 solutions of the quenched melts, implying that the extracted quenched melts actually represent the original melt composition as far as the SenS8-n species are concerned.The resonances due to the polymeric material in the melts could best be interpreted by the statistical random distribution of selenium and sulfur in the polymeric chains, the probability of occurrence of the different fragments being governed by the overall composition of the melt.As the selenium content increases, the relative amount of selenium bound in the polymer seems to increase at the expense of heterocyclic selenium sulfides.Key words: selenium sulfides; sulfur-selenium melt, 77Se NMR spectroscopy.

Selenium Sulfides, HPLC, Raman Spectra, 77Se NMR Spectra, X-RaySe5S in CS2 solution at 20 deg C spontaneously decomposes to give a mixture of 8 selenium-rich cyclic molecules which have been identified by reversed-phase HPLC and 77Se NMR spectroscopy as Se6, Se7, Se8, Se6S, Se7S, 1,2-Se6S2, 1,5-Se6S2, and 1,4-Se4S2.NMR spectra of Se5S, Se7S, and 1,5-Se6S2 have been measured for the first time; Raman spectra of solid Se5S and Se7S as well as crystal data of Se7S are reported in addition.A mechanism based on nucleophilic attack on Se5S is proposed for the formation of the products.

77Se NMR spectroscopy has been applied to the study of heterocyclic selenium sulfides SenS8-n obtained from the molten mixtures of the elements with up to 50 mol % selenium. The assignment of the spectra was based on the combined information from the spectra of the natural-abundance samples and from those of the corresponding 77Se-enriched samples. The main selenium-containing components in these mixtures were SeS7 and 1,2-Se2S6 with smaller amounts of 1,3-, 1,4-, and 1,5-isomers of Se2S6, 1,2,3-, 1,2,4-, and 1,2,5-isomers of Se3S5, 1,2,3,4-, 1,2,3,5-, 1,2,4,5-, and 1,2,5,6-isomers of Se4S4, the 1,2,3-isomer of Se5S3, and Se8. In addition, Se6, which is in equilibrium with Se8, could be observed in some samples. The most abundant species within the given isomeric series were those having all selenium atoms adjacent to each other. The trends in the chemical shifts and in the 77Se-77Se coupling constants are presented, and the composition of the phases as a function of the initial melt composition is discussed.

Square-planar [Ir(dmpe)2]Cl (dmpe = (CH3)2PCH2CH2P(CH3) 2) reacts with Se8 to form deep red [Ir(Se4)(dmpe)2]Cl, together with small amounts of deep purple [Ir(Se2)(dmpe)2]Cl. The purple compound contains side-on-bonded diselenium and is analogous to the known compounds [Ir(Se2)(dPPe)2]Cl (dppe = (C6H5)2PCH2CH2P(C 6H5)2) and [Rh(Se2)(dmpe)2]Cl. Selenium abstraction with triphenylphosphine converts the Se4 complex to the Se2 complex. An X-ray structure determination on the Se4 complex shows the crystals to be orthorhombic, space group Fddd, with a = 15.406 (5) ?, b = 26.792 (6) ?, c = 50.591 (13) ?, V = 20881.6 ?3, and Z = 32. The cation has cis-octahedral geometry with the Se4 group symmetrically chelated to the iridium at equatorial positions and each dmpe group chelating axial and equatorial positions. The IrSe4 ring has a half-chair conformation, with the two central selenium atoms equidistant from, and on opposite sides of, the plane of the Ir atom and the two coordinated Se atoms. The mean Ir-Se (2.545 ?) and Se-Se (2.307 ?) distances are very similar to the values in [Ir(Se2)(dppe)2]+. SCF-Xα-SW calculations on [Ir(Se4)(PH3)4]+ indicate that the Se4 group in the complex is best described as an excited Se4 molecule. Ir-Se4 bonding is mainly via overlap of Ir 5dyz, 5dz2 and 6px orbitals with Se 4p orbitals. pσ bonds form the main link between the Se atoms in the Se4 group. In an EPA glass at liquid-nitrogen temperature, [Ir(Se4)(dmpe)2]+ shows four absorption bands in the 300-700-nm region. These are assigned to one-electron transitions, with good agreement between the observed and calculated energies. The transitions are predominantly intra Se4 ligand in character. The spin-allowed HOMO → LUMO transition corresponds to a shoulder at ～450 nm and is the lowest energy feature of the spectrum.

The separation of a number of cyclic methylene sulfides and selenides by reversed-phase high-pressure liquid chromatography is reported.The retention times as well as the capacity factors depend in a systematic way on the ring size, the number and kind of chalcogen atoms, and the number of heteronuclear bonds within the ring.These relationships are used to assign the chromatograms of cyclic selenium sulfides of type SenS8-n (n=1-8) prepared in a new reaction from Se2Cl2, SCl2 and potassium iodide and containing all selenium atoms in neighboring positions.Keywords: HPLC, Methylene Sulfides, Methylene Selenides, Selenium Sulfides, Sulfur Heterocycles

Dissolution of crystalline Se8 or extraction of glassy or red amorphous selenium, prepared from aqueous SeO2 by reduction, by organic solvents yields solutions containing Se6, Se7 and Se8 in equilibrium as shown by HPLC.The equilibrium explains the concentration dependence of the molar absorbance of such solutions observed earlier.Since the Raman spectrum of red amorphous selenium does not show any lines due to Se6, Se7 and Se8, a rapid interconversion of selenium molecules in solution at 20 deg C is postulated.Red amorphous selenium may consist of a mixture of small and medium sized ring molecules. - Keywords: Elemental Selenium, Equil ibrium in Solution, HPLC, Amorphous Selenium