- Beyond the conventional number of electrons in M6X12 type metal halide clusters: W6Cl18, (Me4N) 2[W6Cl18], and Cs2[W 6Cl18]
-
Black octahedral single crystals of W6Cl18 were obtained by reducing WCl4 with graphite in a silica tube at 600°C. The single crystal structure refinement (space group R 3, Z = 3, a = b = 1498.9(1) pm, c = 845.47(5) pm) yielded the W6Cl 18 structure, already reported on the basis of X-ray powder data. (Me4N)2[W6Cl18] and Cs 2[W6Cl18] were obtained from methanolic solutions of W6Cl18 with Me4NCl and CsCl, respectively. The structure of (Me4N)2[W 6Cl18] was refined from X-ray single crystal data (space group P 3ml, Z = 1, a = b = 1079.3(1) pm, c = 857.81(7) pm), and the structure of Cs2[W6Cl18] was refined from X-ray powder data (space group P 3, Z = 1, a = b = 932.10(7) pm, c = 853.02(6) pm). The crystal structure of W6Cl18 contains molecular W6Cl18 units arranged as in a cubic closest packing. The structures of (Me4N)2[W6Cl18] and Cs2[W6Cl18] can be considered as derivatives of the W6Cl18 structure in which 2/3 of the W 6Cl18 molecules are substituted by Me4N + ions and Cs+ ions, respectively. The conventional number of 16 electrons/cluster is exceeded in these compounds, with 18 electrons for W6Cl18 and 20 electrons for (Me4N) 2[W6Cl18] and Cs2[W 6Cl18]. Cs2[W6Cl18] exhibits temperature independent paramagnetic behaviour.
- Dill, Simone,Glaser, Jochen,Stroebele, Markus,Tragl, Sonja,Meyer, H.-Juergen
-
-
Read Online
- Phosphorus-centered and phosphinidene-capped tungsten chloride clusters
-
Black crystalline powders of W6PCl17 and W 4(PCl)Cl10 were obtained after reducing WCl6 with red phosphorus at 370 and 500 °C. The crystal structures were determined by single-crystal and powder X-ray
- Stroebele, Markus,Eichele, Klaus,Meyer, H.-Juergen
-
-
Read Online
- KINETICS OF TUNGSTEN ETCHING BY ATOMIC AND MOLECULAR CHLORINE.
-
The reactions of atomic and molecular chlorine with tungsten were studied by modulated beam-mass spectrometric methods over the temperature range 300-1350 K. The atomic beam was generated by an rf plasma discharge. With both atomic and molecualr beams, the main reaction product up to about 1000 K was WCl//4. The reaction probability with atomic chlorine was a factor of approximately ten higher than that obtained with molecular chlorine. The reaction was nonlinear with respect to Cl//2 intensity at low beam fluxes but approached linearity at high beam intensities. Above 1000 K the main reaction product was atomic chlorine. Its reaction probability increased rapidly with temperature; at 1300 K nearly complete dissociation of Cl//2 was observed. A kinetic model based on the Eley-Rideal mechanism was proposed and compared with the data. AA. 20 Refs.
- Balooch,Fischl,Olander,Siekhaus
-
-
Read Online
- Synthesis of Alkyne Metathesis Catalysts from Tris(dimethylamido)tungsten Precursors
-
Benzylidyne tungsten systems bearing a combination of alkoxide and amide ligands were readily obtained by partial alcoholysis of amido-supported tungsten complexes. Benzylidyne tris(dimethylamido)tungsten was treated with fluorinated alcohols Me2(CF3)COH, Me(CF3)2COH, and (CF3)3COH, and also with silanols (tBuO)3SiOH, and Ph3SiOH, all of which resulted in complexes of the type [PhC≡W(NHMe2)(NMe2)(OR)2]. Full displacement of the amido ligands was also achieved in [PhC≡W(NHMe2){OC(CF3)2Me}{OSi(O-tBu)3}2] and [PhC≡W(NHMe2)(OSiPh3)3]. In addition, reaction of the three fluorinated alcohols with hexakis(dimethylamido)ditungsten yielded isomeric mixtures of bimetallic complexes [W2(NMe2)4(OR)2], which bear two electron-donating ligands and one electron-withdrawing ligand per tungsten atom. All amido-substituted compounds are active in the self-metathesis of 5-benzyloxy-2-pentyne, although [W2(OR)2(NMe2)4] complexes require longer initiation times depending on the degree of fluorination of the tert-butoxide ligand.
- àrias, òscar,Freytag, Matthias,Jones, Peter G.,Melcher, Daniel,Tamm, Matthias
-
-
Read Online
- Synthesis and characterization of carbon- and nitrogen-centered (Z) trigonal prismatic tungsten clusters of the formula type A[W6ZCl 18]
-
Solid state reactions of tungsten(IV) chloride and carbodiimides (cyanamides) of lithium, sodium, calcium and silver yielded black crystalline powders of centered (Z) trigonal-prismatic tungsten cluster compounds having the general formula A[W6ZCl18] with A = Li, Na, Ca, Ag and Z = C, N. Crystal structures of the corresponding compounds were investigated by powder and single-crystal X-ray diffraction. The nature of the central atom was studied by mass spectrometry and nuclear magnetic resonance spectrometry. It turned out that the central atom can be C (in the case of the lithium and sodium compound) or N (in the case of the sodium and calcium compound).
- Weisser, Martina,Burgert, Ralf,Schnoeckel, Hansgeorg,Meyer, H.-Juergen
-
-
Read Online
- Facile Reduction of Tungsten Halides with Nonconventional, Mild Reductants. I. Tungsten Tetrachloride: Several Convenient Solid-State Syntheses, a Solution Synthesis of Highly Reactive (WCI4)x, and the Molecular Structure of Polymeric Tungsten Tetrachloride
-
Polymeric (WCl4)X has been prepared in crystalline form from WCl6 by three new, safer solid-state approaches via mercury (in 83% yield), bismuth (82% yield), or antimony (97% yield) reduction. A modification of a published procedure for reduction of WCl6 with red phosphorus, which improves (WCl4)x purity, is also described. Highly reactive (WCl4)xpowder can be prepared in 99% yield via tin reduction of WCl6 in 1,2-dichloroethane. (WCl4)x powder was readily converted in high yields to the known WCl4(MeCN)2 and W2Cl4(OMe)4(HOMe)2. The molecular structure of (WCl4)x, as determined by single-crystal X-ray diffractometry, consists of a polymer of opposite-edge-sharing bioctahedra with alternating short (W(1)-W(1A), 2.688(2) ?) and long (W(1)?W(1B), 3.787(3) ?) tungsten - tungsten distances. The acute W(1)-Cl(2)-W(1A) angle (69.4(2)°), obtuse C1(1)-W(1)W(1A) angle (94.99(12)°), short axial Cl(1)?Cl(1A) nonbonded distance (3.085(10) ?, substantially less than twice the Cl van der Waals radius), and short W(1)-W(1A) distance are consistent with a strong W(1)-W(1A) interaction best described as a W=W bond for this d2-d2 compound. Crystal data: Cl4W, a = 11.782(3) ?, b = 6.475(1) ?, c = 8.062(2) ?, β= 131.14(1)°, V = 463.2(2) ?3, monoclinic, C2/m, Z = 4.
- Kolesnichenko, Vladimir,Swenson, Dale C.,Messerle, Louis
-
-
Read Online
- Two tungsten nitride chlorides: W2NCl8 and W 2NCl9
-
A solid state reaction of tungsten(VI)chloride and cyanamide yielded black crystals of W2NCl8 and red plate-like crystals of W 2NCl9. The structures of these compounds were determined by single crystal X-ray diffraction. The crystal structure of W 2NCl8 contains [Cl2/2Cl3WNWCl 3Cl2/2]-units forming chains along the c-axis. The tungsten atoms are linked by a symmetric nitrido bridge (d(W-N) = 1.8203(4) A). The crystal structure of W2NCl9 contains a dichloro-bridged dimer of a nitride-bridged ditungsten unit [Cl 5WNWCl3Cl2/2]2 with two different W-N distances of 1.726(9) A and 2.012(9) A.
- Weisser, Martina,Tragl, Sonja,Meyer, H.-Juergen
-
-
Read Online
- Compounds with the electron-rich [W6Cl18] 2- cluster anion
-
Cluster compounds of the general formula A2[W6Cl 18] containing singly charged A cations (A = K, Rb, Ag, Tl, NH 4, N(C2H5)4, N(n-C3N 7)4, N(n-Cs
- Tragl, Sonja,Stroebele, Markus,Glaser, Jochen,Vicent, Cristian,Llusar, Rosa,Meyer, H.-Juergen
-
-
Read Online
- Unprecedented W2(0) quadruply bonded complex supported by π-donor ligands
-
A quadruply bonded complex W2(DippF)2K2 with a W2(0) core was synthesized and structurally characterized. The observed W-W distance of 2.407(1) ? and DFT calculations are consistent to the unprecedented electronic structure in D2h symmetry of σ2π2π2δ2 δ2δ?2 where the HOMO is the δ? orbital.
- Ventura,Prat,Aguirre Quintana,Goos,Villagran
-
supporting information
p. 3974 - 3976
(2016/03/16)
-
- Salt-free reducing reagent of bis(trimethylsilyl)cyclohexadiene mediates multielectron reduction of chloride complexes of W(VI) and W(IV)
-
We developed a salt-free reduction of WCl6 using 1-methyl-3,6-bis(trimethylsilyl)-1,4-cyclohexadiene (MBTCD) in toluene to give a low-valent trinulcear tungsten complex involving W(II) and W(III) centers, while in the presence of redox active ligands such as α-diketone and α-diimine the same reduction produced W(IV) complexes with the corresponding redox-active ligands, (α-diketone)WCl4 and (α-diimine)WCl4. A W(VI) complex with two α-diketone ligands, (α-diketone)2WCl2, was found to be synthetically equivalent to low-valent W(IV) species that trapped azopyridine to give (α-diketone)WCl2(azopyridine).
- Tsurugi, Hayato,Tanahashi, Hiromasa,Nishiyama, Haruka,Fegler, Waldemar,Saito, Teruhiko,Sauer, Andreas,Okuda, Jun,Mashima, Kazushi
-
p. 5986 - 5989
(2013/05/23)
-
- Kinetic study of Hubnerite (MnWO4) chlorination
-
The kinetics of Argentinean Hubnerite (MnWO4) chlorination using gaseous chlorine as chlorination agent was studied between 750 and 950 °C. The relative mass change during the chlorination reaction was continuously monitored using a high resolution thermogravimetric system. The starting temperature for the reaction of the manganese tungstate with chlorine was determined at about 650°C. The influence of gaseous flow rate, sample mass, chlorine partial pressure, and temperature on the reaction rate was analyzed. The dependence of the reaction rate with sample mass clearly indicates that the reaction is not occurring under chemical control, so the reaction proceeds under mixed control for sample masses greater than 0.5 mg. In those conditions, an apparent activation energy of 198 ± 9 kJ mol-1 was obtained with an isoconversional method. Concerning the influence of chlorine partial pressure, it was determined that pressures greater than 35 kPa do not modify the kinetic regime. For the experiment at 850°C, it was found that the chlorination rate was proportional to a potential function of the partial pressure of chlorine whose exponent is around 0.85. Finally, a global rate equation that includes these parameters was developed.
- Fouga,Taddeo,Bosco,Bohé
-
-
- W6Cl18: New Syntheses, New Structure Refinement, Electronic Structure, and Magnetism
-
Pure W6Cl18 was synthesized after two methods, by oxidizing W6Cl12 with CCl4 in an autoclave, and by reaction of W6Cl12 in a chlorine gas flow. At temperatures above 400°C and under atmospheric pressure W6Cl18transforms into W6Cl12. The crystal structure of W6Cl18 was refined aft er the Rietveld method on X-ray powder data. The unusual electronic conditions of the 18 electron cluster [W6Cl12]Cl6 are compared with those ofthe electron-precise 24 electron cluster [W6Cl8]Cl4. The compound exhib its paramagnetic behaviour with two electrons in antibonding energy levels.
- Naegele, Andreas,Glaser, Jochen,Meyer, H.-Juergen
-
-
- Crystal Structures of Transition-Metal Halides TiCl4, α-TiCl3, WCl4, and TiI2
-
The crystal structures of halides TiCl4, α-TiCl3 (low-temperature modification), WCl4, and TiI2 are determined. The crystals of TiCl4 are built of tetrahedral molecules with Ti-Cl distances of 2.156-2.172 A?. The phase transition in the three-layered modification α-TiCl3 below 220 K is accompanied by the distortion of the symmetry to triclinic and formation of the Ti?Ti pairs spaced by 3.43 A?. The structure of WCl4 contains linear chains of WCl6 octahedra that share opposite edges with the distances of 2.69 A? in the W-W pairs. In the layered structure of TiI2, the titanium atoms occupy the octahedral cavities in the two-layer packing of iodine atoms with a Ti-I distance of 2.903 A?.
- Troyanov,Snigireva
-
p. 580 - 585
(2008/10/08)
-
- Thermal, spectroscopic and kinetic characterization of reaction products of copper(II) chloride with photoproducts of octacyanocomplexes of Molybdenum(IV) and Tungsten(IV) with ethylenediamine
-
The thermal dissociation of complexes formed by copper(II) chloride with photoproducts of M(CN)4-8 [where M=Mo or W] and ethylenediamine has been studied by thermogravimetry (TG), differential scanning calorimetry (DSC) and IR spectroscopy. The observed IR bands for different groups support the assigned composition. Both Mo(IV) and W(IV) show the same stoichiometric behaviour towards complex formation but a different decomposition behaviour. In case of Mo(IV) decomposition takes place in four steps with cyanide and oxide of copper and tetrachloro molybdenum(IV) as residue, while in case of W(IV) the decomposition occurs only in three steps up to 298°C. The copper cyanide along with tetrachloro tungstate(IV) is found as residue. DSC for Mo complex displays four transitions, two exothermic and two endothermic. In case of W, DSC displays three endothermic transitions corresponding to three decomposition steps with three different ΔH values. On the basis of TG and DSC, mechanism for decomposition of each complex has been proposed. Kinetic parameters like activation energy (Ea), frequency factor (A), entropy of activation (ΔS#) for each step has been calculated involving differential methods like Doyle, Coats and Redfern and Arrhenius. The heat of the reaction is obtained from DSC curves.
- Ali,Majid, Kowsar
-
p. 173 - 181
(2008/10/09)
-
- Microwave-assisted Solid-state Reactions involving Metal Powders
-
The ability of metal powders to couple to microwave radiation at 2450 MHz has been used to accelerate a range of solid-state reactions.Although metal objects cause extensive arcing within a microwave cavity, metal powders couple in a more conventional manner with the microwave radiation and experience high heating rates.This property has been utilised for the synthesis of metal chalcogenides and metal cluster compounds of the Group 5 and 6 elements.
- Whittaker, A. Gavin,Mingos, D. Michael P.
-
p. 2073 - 2080
(2007/10/02)
-
- Synthesis and structure of W3S4Cl4
-
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
-
p. 253 - 264
(2008/10/08)
-
- 2-Anilinopyridine complexes of dimolybdenum(II) and ditungsten(II)
-
The reaction of Mo2(O2CCH3)4 with the lithium salt of 2-anilinopyridine in tetrahydrofuran has led to the formation of Mo2(PhNPy)4 (9). The tungsten analogue (10) was prepared by the reduction of WCl4 with 2 equiv of sodium amalgam in tetrahydrofuran followed by the addition of a slight excess of LiPhNpy. Their structures have been determined by X-ray crystallography. The dark red dimolybdenum complex crystallizes in the monoclinic space group P21/c with the following cell dimensions: a = 19.867 (1) ?, b = 9.763 (1) ?, c = 20.082 (1) ?, β = 100.4 (1)°, V = 3831 (2) ?3, Z = 4. The average of the two crystallographically independent Mo-Mo quadruple bond lengths is 2.071 (2) ?. The black-red ditungsten analogue, which crystallizes with two THF molecules per unit cell in the P1 space group, shows the following cell dimensions: a = 10.535 (2) ?, b = 19.194 (3) ?, c = 18.598 (3) ?, α = 107.4 (1)°, β = 99.7 (1)°, V = 103.6 (1)a, V = 3369 (3) ?3, Z = 3. The average W-W quadruple bond length is 2.165 (2) ? (average for three independent molecules per asymmetric unit, located on inversion centers at 0, 0, 0; 1/2, 0, 1/2; and 1/2, 1/2, 1/2). The average M-N(py) and M-Na bond lengths are 2.156 (8) and 2.141 (8) ?, respectively, for the dimolybdenum complex and 2.144 (14) and 2.123 (8) ?, respectively, for the ditungsten complex. The M-M′-N angles lie in the range 91.4-93.0°. Electronic absorption bands that we assign to the δ → δ* transitions were observed at 467 nm for 9 and 520 nm for 10. In 9 there is also a band at 440 nm that is possibly due to a δ → π* transition. Compound 9 in THF displays two one-electron quasi-reversible oxidative responses at 0.00 V (ΔEp = 200 mV) and +0.475 V (ΔEp = 150 mV) vs. Ag-AgCl at 100 mV s-1 with tetrabutylammonium perchlorate as the supporting electrolyte. The oxidation processes are due to successive removal of two electrons from the δ level: (Formula Presented) The ditungsten analogue undergoes a one-electron oxidation at -0.067 V (ΔEp = 130 mV) due to the couple (Formula Presented) and the one-electron reduction at -0.84 V (ΔEp = 140 mV) may be due either to the couple (Formula Presented) or to a ligand reduction. The relationships between the observed δ → δ* transitions and the formal potentials are discussed.
- Chakravarty, Akhil R.,Cotton, F. Albert,Shamshoum, Edwar S.
-
p. 4216 - 4221
(2008/10/08)
-
- Preparation of W2Cl84- and several of its derivatives
-
The sodium amalgam reduction of WCl4 in tetrahydrofuran in the presence of a tertiary phosphine (L = PMe3, PBu3, PMe2Ph, PMePh2) produces a family of compounds of the type W2Cl4L4, which contain a tungsten-tungsten quadruple bond. W2Cl4(dmpe)2 and W2Cl4(dppe)2 must be prepared by the reaction between W2Cl4(PBu3)4 and dmpe or dppe. In the absence of phosphine, WCl4 can be reduced to W2Cl6(THF)4. W2Cl6(THF)4 reacts with phosphine to produce W2Cl6L4, and W2Cl6L4 can be reduced cleanly to W2Cl4L4. In the absence of phosphine W2Cl6(THF)4 can be reduced to deep blue Na4(THF)xW2Cl8. Several other derivatives such as Na4(TMEDA)4W2Cl8 have also been prepared. All derivatives that contain the W2Cl84- ion decompose within a few minutes at 25°C in solvents in which they dissolve. Na4(THF)xW2Cl8 reacts rapidly with phosphine to produce W2Cl4L4, with 6-methyl-2-hydroxypyridine in the presence of triethylamine to produce W2(mhp)4, and with pivalic acid in the presence of triethylamine to produce W2(O2CCMe3)4. We have shown that complexes of the type W2Cl4L4 can be oxidized readily to monocations. An attempt to prepare W2(O2CCH3)4 from W2Cl4(PBu3)4 and acetic acid also led to oxidation of the metal to give W3O3Cl5(O2CCH3)(PBu 3)3.
- Schrock, Richard R.,Sturgeoff, Lynda G.,Sharp, Paul R.
-
p. 2801 - 2806
(2008/10/08)
-