- Oleum and sulfuric acid as reaction media: Structural features and thermal behavior of RE2[W2O3(SO4) 6] (RE = Sm-Gd, Ho), RE2Nb2O 2(SO4)3[H(SO4)2] 2 (RE = Y, Ce-Nd, Sm-Er)
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The first examples of ternary sulfates containing refractory metals and trivalent ions of the rare-earth group and bismuth were prepared by solvothermal synthesis from H2SO4/SO3 mixtures. The tungsten compounds RE2[W2O3(SO 4)6] (RE = Sm-Gd, Ho) were obtained by the reaction of WOCl4 and RE2O3 in oleum (25 % SO3). They crystallize in the monoclinic space group C2/c and contain the unique [W2O3(SO4)6]6- anion. Thermal decomposition leads to the oxides RE2O(WO4) 2. Tetragonal rare-earth-niobium sulfates of the type RE 2Nb2O2(SO4)3[H(SO 4)2]2 (RE = Y, Ce-Nd, Sm-Er) (space group P421m) were synthesised from NbCl5 and RE 2O3 in 100 % H2SO4. They contain [O3SO...H...OSO3]3- ions featuring a strong hydrogen bond and form a polymeric structure with niobium in an octahedral coordination and the rare-earth ion is surrounded by eight [SO 4] tetrahedra in the form of a square antiprism. The decomposition temperature of RE2Nb2O2(SO4) 3[H(SO4)2]2 depends on the size of the respective rare-earth ion with a maximum in thermal stability found for RE = Sm-Gd (≈550 °C). The reaction of NbCl5 and Sm(NO 3)3·6H2O in oleum (25 % SO3) yielded Sm2Nb2O2(SO4) 5(S2O7), which is a possible intermediate of the thermal decomposition of Sm2Nb2O2(SO 4)3[H(SO4)2]2. It crystallizes in the monoclinic space group I2/a and contains 2 ∞[NbO(SO4)2/2(SO4) 3/3] layers connected by 2∞[Sm(SO 4)2/4(S2O7)2/4] units to a polymeric structure. Reaction of NbCl5 with (BiO) 2CO3 or Eu2O3 in 95 % H 2SO4 yielded M2Nb4O 5(SO4)8 (M = Bi, Eu, monoclinic, space group C2/c). These compounds contain the unprecedented [M2Nb 4O5]16+ cluster cation and decompose into MNbO4 and Nb2O5 on heating. Copyright
- Betke, Ulf,Wickleder, Mathias S.
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- Edge-bridged octahedral tungsten-oxygen-chlorine clusters: Synthesis and characterization of two D3d-symmetric [W6O6Cl12]2- isomers and [W6O7Cl11]3-
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Initial access to the chemistry of hexanuclear tungsten oxohalide clusters is provided through the reduction of WOCl4 with bismuth metal at 360 °C. Reactions targeting W6O6Cl10 produce an amorphous black solid, which, upon treatment with concentrated aqueous HCl, releases the edge-bridged octahedral cluster [α-W6O6Cl12]2- into solution. The cluster exhibits a D3d-symmetry structure in which the six oxygen atoms bridge the edges between two opposing triangular faces of a trigonally compressed W6 octahedron. Reactions incorporating additional bismuth metal yield a mixture of soluble clusters, including a 5:7 ratio of (α-W6O6Cl12]2- and another D3d-symmetry isomer, [β-W6O6Cl12]2-. The latter species displays a different core structure, in which the six oxygen atoms are situated on the edges comprising two opposing triangular faces of a trigonally elongated W6 octahedron. Isolated as the BuN+ salts, the two isomers can be separated by a process relying on the differences in crystal morphology. Cyclic voltammetry of acetonitrile solutions shows two reversible one-electron reductions for each cluster, the α isomer being slightly more easily reduced. Density functional theory calculations indicate that the two isomers of [W6O6Cl12]2- are nearly identical in energy, with the β isomer lying just 1.4 kcal/mol below the α isomer. The other major product isolated from the reaction with additional bismuth is [W6O7Cl11]3-, a cluster at least formally related to [β-W6O6Cl12]2- by substitution of an O2- ion for a core Cl- ion. In acetonitrile solution, this cluster displays a single reversible one-electron reduction. It is anticipated that the reactions elaborated here will lead to a general method for synthesizing metastable metal oxohalide clusters.
- Crawford,Long
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- Sulfates of the refractory metals: Crystal structure and thermal behavior of Nb2O2(SO4)3, MoO 2(SO4),WO(SO4)2, and two modifications of Re2O5(SO4)2
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The sulfates Nb2O2(SO4)3, MoO2(SO4),WO(SO4)2, and two modifications of Re2O5(SO4)2 have been synthesized by the solvothermal reaction of NbCl5, WOCl 5,Re2O7(H2O)2, and MoO3 with sulfuric acid/SO3 mixtures at temperatures between 200 and 300 °C. Besides the X-ray crystal structure determination of all compounds, the thermal behavior was investigated using thermogravimetric studies. WO(SO 4)2 (monoclinic, P21/n, a = 7.453(1) A, b = 11.8232(8) A, c=7.881 (1) A, β = 107.92(2)°, V = 660.7(1) A3, Z =4) and both modifications of Re2O 5(SO4)2 (I: orthorhombic, Pba2, a = 9.649(1) A, b=8.4260(8)A, c = 5.9075(7)A, V = 480.27(9) A3, Z = 2; II: orthorhombic, Pbcm, a = 7.1544(3) A, b = 7.1619(3) A, c =16.8551 (7) A, V =863.64(6) A3, Z =4) are the first structurally characterized examples of tungsten and rhenium oxide sulfates. Their crystal structure contains layers of sulfate connected [W=O] moieties or [Re2O5] units, respectively. The cohesion between layers is realized through weak M-O contacts (343-380 pm).Nb2O2(SO4)3 (orthorhombic, Pna21, a = 9.9589(7) A, b = 11.7983(7) A, c = 8.6065(5) A, V =1011.3(1) A3, Z =4) represents a new sulfate-richer niobium oxide sulfate. The crystal structure contains a three-dimensional network of sulfate connected [Nb=O] moieties. In MoO 2(SO4)(monoclinic, 12/a, a = 8.5922(6) A, b =12.2951 (6) A, c = 25.671 (2) A β = 94.567(9)°, V = 2703.4(3) A3, Z =24)[MoO2] units are connected through sulfate ions to a three-dimensional network, which is pervaded by channels along [100] accommodating the terminal oxide ligands. In all compounds except WO(SO 4)2,the metal ions are octahedrally coordinated by monodentate sulfate ions and oxide ligands forming short M=O bonds. In WO(SO4)2, the oxide ligand and two monodentate and two bidentate sulfate ions build a pentagonal bipyramid around W. The thermal stability of the sulfates decreases in the order Nb > Mo > W > Re; the residues formed during the decomposition are the corresponding oxides.
- Betke, Ulf,Wickleder, Mathias S.
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- METAL ORGANIC COMPOUNDS
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The invention concerns a process for preparing an essentially silicon (Si) free compounds of the general formula [M(O)(OR)y], wherein M = Mo, y = 3 or M = W, y = 3 or 4. Furthermore, it is directed towards compounds obtained by the aforementioned process and towards the use of such an obtained compound. Another objective of the herein described invention are essentially silicon free compounds of the general formula MOXy or [MOXy(solv)p], prepared using the aforementioned process, wherein M = Mo, y = 3 or M = W, y = 3 or 4, X = Cl or Br, solv = an oxidizing agent Z binding or coordinating to M via at least one donor atom, p = 1 or 2. The invention is also directed towards the use of essentially silicon free compounds prepared using the aforementioned process of the general formula MOXy or [MOXy(solv)p].
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Page/Page column 93; 95
(2021/10/11)
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- Complexes of WOCl4 and WSCl4 with neutral N- and O-donor ligands: Synthesis, spectroscopy and structures
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The complexes [WOCl4(L)] and [WSCl4(L)] (L = OPPh3, OPMe3, pyridine, 2,2′-bipyridyl), [{WOCl4}2(μ-L-L)] and [{WSCl4}2(μ-L-L)] (L-L = Ph2P(O)(CH2)nP(O)Ph2 (n = 1, 2)) have been prepared from WOCl4 or WSCl4 and the ligands in anhydrous CH2Cl2 solution, and characterised by microanalysis, IR and NMR (1H, 31P{1H}) spectroscopy. X-Ray crystal structures are reported for [WOCl4(OPPh3)], [{WOCl4}2(μ-Ph2P(O)(CH2)P(O)Ph2)] and [{WSCl4}2(μ-Ph2P(O)(CH2)2P(O)Ph2)]. All, except those of 2,2′-bipyridyl, are six-coordinate with the neutral donor trans to W[dbnd]O or W[dbnd]S. Spectroscopic data suggest that the [WOCl4(2,2′-bipy)] and [WSCl4(2,2′-bipy)] are seven-coordinate. Comparison of the structural and spectroscopic data for the two series of complexes indicate little difference in Lewis acidity between the two tungsten(VI) moieties. Decomposition of [WOCl4(OPMe3)] in solution gave the cyclic trimer [W3O3(μ-O)3Cl6(OPMe3)3], the structure of which revealed a six-membered W3O3 ring core with very asymmetric oxido-bridges. The structure of the tungsten(V) complex [WOCl3(2,2′-bipy)] is also reported.
- Greenacre, Victoria K.,Hector, Andrew L.,Levason, William,Reid, Gillian,Smith, Danielle E.,Sutcliffe, Laura
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- TUNGSTEN PRECURSOR AND METHOD OF FORMING TUNGSTEN CONTAINING LAYER USING THE SAME
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Disclosed is a tungsten precursor and a method of forming a tungsten-containing layer. The tungsten precursor has a structure represented by Formula 1 below. In Formula 1, R1, R2, and R3 independently include a straight-chained or a branched alkyl group including a substituted or an unsubstituted C1-C5; R4 and R5 independently include a straight-chained or a branched alkyl group including a C1-C5, halogen element, dialkylamino group having C2-C10, or trialkylsilyl group including a C3-C12; n is 1 or 2, and m is 0 or 1. Also, n+m=2 (e.g., when n is 1, m is 1). When n is 2, m is 0 and each of R1 and R2 are provided in two. Two R1s are independently of each other, and two R2s are independently of each other.
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Paragraph 0024; 0026
(2019/01/04)
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- Substitution of conventional high-temperature syntheses of inorganic compounds by near-room-temperature syntheses in ionic liquids
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The high-temperature syntheses of the low-valent halogenides P2I4, Te2Br, a-Te4I4, Te4(Al2Cl7)2, Te4(Bi6Cl20), Te8(Bi4Cl14), Bi8(AlCl4)2, Bi6Cl7, and Bi6Br7, as well as of WSCl4 andWOCl4 have been replaced by resource-efficient low-temperature syntheses in room temperature ionic liquids (RTILs). The simple one-pot syntheses generally do not require elaborate equipment such as twozone furnaces or evacuated silica ampoules. Compared to the published conventional approaches, reduction of reaction time (up to 80%) and temperature (up to 500 K) and, simultaneously, an increase in yield were achieved. In the majority of cases, the solid products were phase-pure. X-Ray diffraction on single crystals (redetermination of 11 crystal structures) has demonstrated that the quality of the crystals from RTILs is comparable to that of products obtained by chemical transport reactions.
- Groh, Matthias F.,Muller, Ulrike,Ahmed, Ejaz,Rothenberger, Alexander,Ruck, Michael
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p. 1108 - 1122
(2013/12/04)
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- Mixed valence tungsten (IV,V) compounds with layered structures (Part III)[2]: Synthesis and crystal structure of Ag1-x[W2O 2Cl6] and investigations on the Ag+ ion mobility
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The reaction of metallic silver with tungsten tetrachlorideoxide WOCl4 or the reaction of AgCl with WOCl3, both at 690 K, lead to Ag 1-x[W2O2Cl6] as black lustrous crystal needles. The compound shows a substantial phase field width in the silver content depending on reaction temperature and reaction time and crystals with x = 0, 0.38 and 0.82 were isolated. The crystal structure determinations (monoclinic, C2/m) show the structure to be isotypic to those of Tl[W 2O2Cl6] and K0.84[W 2O2Cl6] with the presence of 1D polymeric [W2O2Cl6]n strands and Ag+ ions with a variety in the occupation of the respective crystallographic site. Ag 1-x[W2O2Cl6] represents a mixed valence compound with a variable ratio of W(IV) and W(V) in the W2 dumbbells with a short W-W separation of 2.85 A. In Fourier maps the electron density of the Ag ion appears smeared over a large area. By structure determinations of stoichiometric Ag1.0[W2O 2Cl6] at temperatures of123, 193, and 293 K a double minimum potential was found with the silver ion dynamically disordered over two flat basins with a thermal activation barrier of 13 meV. No long range ion mobility is present since the Ag+ ions are trapped within a coordinating cage consisting of ten chlorine atoms of the surrounding [W 2O2Cl6] strands forming a distorted bicapped cube. By MAS-NMR spectroscopic measurements on the 109Ag nuclei at different temperatures, the spin lattice relaxation times were determined giving a thermally activated barrier of 15 meV. The electronic conductivity of pressed powder samples of Ag[W2O2Cl6] by a four-probe measurement applying direct current is 1Ω-1·cm -1 at room temperature and 10-3Ω -1·cm-1 at 25 K. For the conduction mechanism at low temperatures a variable range hopping mechanism is suggested, whereas at higher temperatures a standard semi-conductivity with a bandgap of 60 meV is present.
- Beck, Johannes,Hoffbauer, Wilfried,Kusterer, Christian,Schieweling, Marcel
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p. 1827 - 1833
(2011/01/05)
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- Synthesis and characterisation of tungsten siloxides including the crystal structure of [WO{O(Ph2SiO)3}2(thf)]
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Reactions of WOCl4 with NaOSiPh3 and Na2O2SiPh2 gave respectively [WO(Cl)(OSiPh3)3] and [{WO2[(OSiPh2)2O]}2]. Under similar conditions NaOSiPh3 reacted with [WO2Cl2(OSC4H8)2] to yield [WO2(OSiPh3)2(OSC4H 8)2]. The novel spirocyclic tungstasiloxane [WO{O(Ph2SiO)3}2(thf)] was prepared from the reaction between equimolar quantities of (Ph2SiO)3 and WOCl4 in tetrahydrofuran. A crystal structure determination on this product revealed a distorted octahedral geometry about the central tungsten atom with the axially co-ordinated ether ligand trans to the oxo group, and puckered eight-membered siloxane rings oriented on opposite sides of the equatorial plane defined by the four co-ordinated siloxide O atoms. The W-O (Si) separations ranged from 1.851(7) to 1.896(8) A and the W=O bond length was 1.675(13) A. In dichloromethane WCl6 reacted with (Ph2SiO)3 to afford good yields of WOCl4, whereas in tetrahydrofuran the same reactants caused solvent polymerisation.
- Brisdon, Brian J.,Mahon, Mary F.,Rainford, Christopher C.
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p. 3295 - 3299
(2007/10/03)
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- Synthesis and structure of W3S4Cl4
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The synthesis of W3S4Cl4, a layered tungsten thiohalide with a basic structure similar to TiS3 is described. W3S4Cl4 was synthesized from WCl2 and sulfur at 350°C. The X-ray powder diffraction pattern was completely indexed on a small hexagonal unit cell with a = 3.336(1) A and c = 5.907(1) A. Electron diffraction studies revealed a 4 × 4 × 8 supercell, giving the compound a superstructure with a = 13.356 A and c = 47.29 A. An ordering of the tungsten vacancies which can account for this superstructure is discussed in light of the electron diffraction patterns.
- Rauch,DiSalvo,Zhou,Tang,Edwards
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p. 253 - 264
(2008/10/08)
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- Further studies of imido alkylidene complexes of tungsten, well-characterized olefin metathesis catalysts with controllable activity
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An alternative synthesis of W(CH-t-Bu)(NAr)(dme)Cl2 (Ar = 2,6-C6-H3-i-Pr2) consists of the five steps WCl6 → W(O)Cl4 → W(NAr)Cl4 → W(NAr)(O-t-Bu)2Cl2(THF) → W(NAr)(O-t-Bu)2(CH2-t-Bu)2 → W-(CH-t-Bu)(NAr)(dme)Cl2, in which tert-butoxide "protecting groups" are replaced by chlorides in the last step upon addition of PCl5. The easiest synthesis to a catalyst precursor consists of the three steps WO2Cl2 → W(NAr)2Cl2(dme) → W(NAr)2(CH2R)2 → W(CHR)(NAr)(OTf)2(dme) (R = t-Bu, CMe2Ph; OTf = OSO2CF3), in which an imido ligand protecting group is ultimately replaced by two triflate ligands upon addition of triflic acid in the last step. An X-ray study of W(CH-t-Bu)(NAr)(O-t-Bu)2 shows it to be a pseudotetrahedral complex in which the tert-butyl group points toward the imido ligand (syn conformation; space group P1, a = 14.050 (5) ?, b = 18.885 (5) ?, c = 11.123 (5) ?, α = 92.22 (3)°, β = 108.30 (3)°, γ = 79.25 (2)°, V = 2752 (2) ?3, Z = 4, Mr 572.46, ρ = 1.381 g cm-3, μ = 43.03 cm-1; R = 0.039, Rw = 0.043). Complexes of the type W(CH-t-Bu)(NAr′)(OR)2 (NAr′ = N-2,6-C6H3Me2; OR = O-t-Bu, OCMe2(CF3), OCMe(CF3)2, OC(CF3)2(CF2CF2CF3)) were prepared by methods analogous to those used originally to prepare NAr complexes. Reactions between NAr′ complexes and olefins in general yield less stable organometallic products than when the NAr ligand is present. In one case (addition of internal olefins to W(CH-t-Bu)(NAr′)[OCMe(CF3)2]2) a product was isolated that was consistent with the formation {W(NAr′)-[OCMe(CF3)2]2}2. Some of the W(CH-t-Bu)(NAr)X2 variations that were prepared include X = OAr, OCEt3, OCMe2Ph, SAr, and CH2-t-Bu. Other variations include W(CHEt)(NAr)X2 complexes (X = OCEt3, NPh2), W(CHSiMe3)(NAr)X2 complexes (X = OAr, OCMe2(CF3), OCMe(CF3)2), and W[CHSi(OMe)3](NAr)X2 complexes (X = OAr, OCMe2(CF3), OCMe(CF3)2). Syn and anti rotamers of W(CHSiMe3)(NAr)(OAr)2 were observed and found to interconvert on the NMR time scale (ΔG?298 = 15.0 (1) kcal mol-1). None of the variations have any obvious advantage over known alkoxide/NAr complexes for metathesis of ordinary or strained cyclic olefins. An attempt to prepare a derivative containing the OC(CF3)2(tolyl) ligand yielded W[OC(C6H3Me)(CF3)2](NAr)[OC(CF 3)2(tolyl)](CH2-t-Bu), formed by addition of an ortho CH bond to the W=C bond (space group P21/c, a = 16.821 (2) ?, b = 11.951 (1) ?, c = 19.455 (4) ?, β = 93.852 (8)°, V = 3920.5 ?3, Z = 4, Mr 943.6, ρ(calcd) = 1.606 g cm-3, μ = 31.09 cm-1; R = 0.038, Rw = 0.043).
- Schrock,DePue,Feldman,Yap,Yang,Davis,Park,DiMare,Schofield,Anhaus,Walborsky,Evitt,Krüger,Betz
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p. 2262 - 2275
(2008/10/08)
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- N-Chloro-Nitrene Complexes of Tungsten: WCl4(NCl) and
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WCl4(NCl) has been prepared as a red-brown crystal powder by the reaction of tungsten hexacarbonyl with excess nitrogen trichloride in boiling CCl4.The complex is associated via chloro bridges, forming dimeric units, according to the IR spectrum.Thermal decomposition at 200 deg C leads to tungsten nitride trichloride, WNCl3.With acetonitrile, WCl4(NCl) reacts with formation of the monomeric complex , which was characterized by its IR spectrum as well as by an X-ray structure determination.Crystal data: space group P21/m, Z = 2 (1387 independent observed reflexions, R = 0.07).Lattice dimensions at 20 deg C: a = 590.4(3), b = 729.0(3), c = 1124.6(4) pm, β = 100.63(2) deg.The complex forms monomeric molecules, in which the tungsten atom has a distorted octahedral environment of four chlorine atoms in equatorial positions, and the acetonitrile molecule in trans-position to the W(-)N(+)-Cl group.Bond lengths WN = 172 and NCl = 161 pm; bond angle WNCl = 175.5 deg. -Keywords: Synthesis, IR Spectra, X-Ray, N-Chloro-Nitrene-Tungsten Tetrachloride, Acetonitrile Adduct
- Goerge, Astrid,Dehnicke, Kurt,Fenske, Dieter
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p. 677 - 681
(2007/10/02)
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- EFFECT OF CARBOXYLIC ACIDS ON THE METATHESIS OF METHYL 10-UNDECENOATE.
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The metathesis of esters of unsaturated carboxylic acids catalyzed by the WCl//6/Me//4Sn system is influenced by the presence of free acids. The extent of their effect depends on how they are delivered into the reaction mixture. If the acid is allowed to
- Balcar,Dosedlova,Matyska
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p. 367 - 374
(2008/10/08)
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- Chemistry of o-Xylidene-Metal Complexes. Part 3. Tungsten o-Xylidene Complexes derived from Tetrachloro(oxo)tungsten(IV); X-Ray Crystal Structures of *0.5C6H6 and
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Reaction of WCl4O with the di-Grignard reagent o-C6H4(CH2MgCl)2 or the chloride-free 'o-xylidene' complex Mg(CH2C6H4CH2-o) (thf) in tetrahydrofuran (thf) yields either the thermally stable tris(chelate), (7), or the Wv complex (8) (a non-electrolyte in thf), in a manner critically dependent on reaction conditions.In both reactions a reduction step precedes alkylation, as determined by e.s.r., with probable intermediates being -, 2-, and .The complex (7) undergoes reversible one-electron reduction as shown by cyclic voltammetry, Ered = -1.68 V, and the Wv radical anion gav = 2.005,is also accessible from (7) and sodium dihydronaphthylide.X-Ray analysis shows that the o-xylenidyl ligand (1) behaves as a chelating ligand in both (7) and (8), but in (8) the two ligands (1) are bonded differently.One is typically metallacyclic in nature, W-Cα 2.16(2) Angstroem, W-Cα-C(aromatic) 109(1) deg with a fold angle (Φ) of 42.4 deg, whereas the other has a larger Φ (66.1 deg) with α> 2.16(4) Angstroem, and W-Cα-C(aromatic) 98(2) and 93(1) deg, possibly arising from an aromatic ? interaction with the tungsten atom.For the tris(chelate) (7) all ligands are equivalent, the tungsten symmetry is quasi-3/m, with a more pronounced W-?-arene interaction, possibly of a stabilising influence 1, W-C(aromatic) 2.49 Angstroem; W-C-C(aromatic) 82.7 deg, Φ = 83.3 deg>.In complex (8), the magnesium atom is octahedrally co-ordinated, with the four thf ligands disposed equatorially; the WO bond is short, 1.71(1) Angstroem.
- Lappert, Michael F.,Raston, Colin L.,Rowbottom, Graham L.,Skelton, Brian W.,White, Allan H.
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p. 883 - 892
(2007/10/02)
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- Tellurium-nitrogen compounds
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With H2N-TeF5 and (CH3)3SiNHTeF5 as the starting materials numerous new tellurium-nitrogen compounds have been synthesized. Almost all of them contain the >N-TeF5 group, which stabilizes many double-bonded systems such as O=C=NTeF5 and Cl4W=NTeF5. Cl2Se=NTeF5 is a rare example of a compound containing a discrete selenium-nitrogen double bond.
- Hartl, Hans,Huppmann, Peter,Lentz, Dieter,Seppelt, Konrad
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p. 2183 - 2187
(2008/10/08)
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- Oxygen, Sulphur, and Selenium Abstraction from WCl4Y (Y = O, S, or Se) by Triphenylphosphine. Crystal and Molecular Structure of Tetrachlorobis(triphenylphosphine)tungsten(IV)
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Excess of triphenylphosphine has been allowed to react with the series of compounds WCl4Y (Y = O, S, or Se).The products from each reaction have been analysed and subjected to spectroscopic studies which have shown that in each reaction abstraction of the chalcogen atom took place thus reducing tungsten(VI) to tungsten(IV) and yielding WCl4*2PPh3 and P(Y)Ph3.With Y = O a second product, WCl4O*P(O)Ph3*PPh3, was also isolated.The complex WCl4*2PPh3 crystallises in the monoclinic space group P21/n, with a = 9.605(8), b = 21.320(13), c = 9.313(8) Angstroem, β = 117.5(1) deg, and Z = 2.The WCl4*2PPh3 molecules are centrosymmetric with two equivalent W-Cl distances and a long W-P distance .
- Drew, Michael G. B.,Page, Elizabeth M.,Rice, David A.
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- The Reactivity of Molybdenum and Tugsten Trioxide Vapours towards Organic and Inorganic Compounds at -196 deg C
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Vapours of molybdenum and tungsten trioxides, prepared by heating the solid oxides under vacuum, have been reacted with organic compounds and some inorganic halides at -196 deg C.Complexes of the trioxides are formed with pentane-2,4-dione, acetone, formic acid, and methanol, but the oxides fail to bring about metathesis or isomerisation of olefins.Oxygen-halogen exchange reactions occur between the trioxides and BCl3, SiCl4, and HCl; PCl3 is oxidised.The reactivity of the condensed vapours of both oxides at -196 deg C is markedly higher than the reactivity of the normal solid oxides at room temperature.
- Cook, Neil D.,Timms, Peter L.
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p. 239 - 244
(2007/10/02)
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- Infrared and Electronic Spectra of Matrix-isolated Dichlorodioxo- and Dibromodioxo-molybdenum(VI) and -tungsten(VI)
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The prominent i.r. and u.v.-visible bands of the title compounds isolated as monomers in low-temperature matrices have been obtained and assigned.For MoO2Cl2 and MoO2Br2, the vibrational isotope effect on the antisymmetric stretching mode ν(Mo=O) leads to estimates of bond angles OMoO of 109 +/- 3 deg., whilst for WO2Cl2 and WO2Br2, relative band intensities predict OWO = 107 +/- 2 deg. for both molecules.In the quantitative assignment of the electronic spectra, it is suggested that the positions of the charge transfer bands require somewhat lower values of χopt. than are appropriate for octahedral complexes.
- Levason, William,Narayanaswamy, Ramaier,Ogden, J. Steven,Rest, Antony J.,Turff, Jeremy W.
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p. 2009 - 2014
(2007/10/02)
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