A comparison of local structures in crystalline P(EO)3LiCF3SO3 and glyme-LiCF3SO3 systems

The newly discovered crystal structures of CH₃(OCH₂CH₂)OCH₃(LiCF₃SO₃)₂, monoglyme:(LiTf)₂, and CH₃(OCH₂CH₂)₃OCH₃(LiCF₃SO₃)₂, triglyme:(LiTf)₂, are briefly described. The coordination of lithium cations and the CF₃SO₃⁻ anions in these structures is compared with the cation and anion coordination in the crystalline phase of high molecular weight P(EO)₃LiCF₃SO₃. Comparison is also made with the previously reported crystalline phase of CH₃(OCH₂CH₂)₂OCH₃LiCF₃SO₃, diglyme:LiTf. A tendency to form trans-gauche-trans conformations for the bond order -O-C-C-O- is noted in adjacent ethylene oxide sequences interacting with a five-coordinate lithium ion.     

The System LiSO3CF3/RbSO3CF3: Phase Diagram,Solid State NMR Investigations,and Ionic Conductivity

In the system LiSO₃CF₃/RbSO₃CF₃ four different quasi‐ternary phases occur: Li_0.7Rb_0.3SO₃CF₃, Li_0.55Rb_0.45SO₃CF₃, LiRb₂(SO₃CF₃)₃, and Li_0.2Rb_0.8SO₃CF₃. These have been identified, and characterized by means of X‐ray powder diffractometry and DSC. LiSO₃CF₃ is trimorphic, LiRb₂(SO₃CF₃)₃ is dimorphic and RbSO₃CF₃ exists in four different modifications. The cation dynamics has been studied using ⁷Li‐NMR line shape analysis and ⁷Li‐spin lattice relaxation (T₁) measurements. The pure and mixed trifluoromethylsulfonates in the system LiSO₃CF₃/RbSO₃CF₃ are solid electrolytes. Their ionic conductivities below 475 K increase with the rubidium content. Above this temperature, the conductivity of β‐LiRb₂(SO₃CF₃)₃ exceeds the one of δ‐RbSO₃CF₃.     

Substituent effects on the disproportionation—combination rate constant ratios for gas‐phase halocarbon radicals,Part 5: Reactions of CF3 + CF3CH2CHCH3 and CF3CH2CHCH3 + CF3CH2CHCH3

Rate constant ratios, k_d/k_c for the disproportionation/combination reaction have been measured as 0.07 ± 0.02 when an H is removed from the CH₂ position of the CF₃CH₂CHCH₃ radical and as 0.24 ± 0.03 when the H is removed from the CH₃ position in the reaction with the CF₃ radical. For the self‐reaction between two CF₃CH₂CHCH₃ radicals, k_d/k_c has been measured as 0.27 ± 0.03 when the H is removed from the CH₂ position and as 0.47 ± 0.04 when the H is removed from the CH₃ position. The branching fraction, corrected for the number of hydrogens at each site, is 0.70 favoring the methyl position when the acceptor radical is CF₃ and 0.54 when CF₃CH₂CHCH₃ is the acceptor radical. Branching fraction results show that the CF₃ substituent on the CF₃CH₂CHCH₃ radical hinders disproportionation when CF₃ is the acceptor radical. When the accepting radical is CF₃CH₂CHCH₃ the CF₃ substituent may slightly impede the disproportionation reaction, but the branching ratio is nearly statistical. The effect of substituents on the donor radical, CF₃CH₂CHX, will be discussed for the series X = H, CF₃, Cl, and CH₃ when the acceptor radical is CF₃. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 549–557, 2001     

Comparaison entre la protolyse du diméthylcadmium et celle d'un alcoolate mixte. Étude des équilibres et des réactions d'échange.

PMR studies show that CH₃CdOC(CH₃)₃ is formed more rapidly than symmetrical alkoxide from (CH₃)₂Cd and (CH₃)₃COH. Spectra of CH₃CdOC(CH₃)₃ in different solvents show that this product is less solvated that (CH₃)₂Cd. An interpretation based on exchange of methyl groups in various cases is proposed.     

Determination of the maximum monolayer dispersion and dispersed state for WO3 on γ-Al2O3

The maximum monolayer dispersion (the threshold) for WO₃ on γ-Al₂O₃ calcined at 500°, 550°, 600°, and 640°C has been determined quantitatively by XRD (amount of crystalline phase) and XPS (intensity ratios I_w4f/I_Al2). The results show that if the amount of WO₃ loaded is lower than the maximum monolayer dispersion, WO₃ will react with γ-Al₂O₃ to form surface compound due to mutual ionic interaction, and will be dispersed on γ-Al₂O₃ surface as monolayer then. In case the amount is higher than this value, the residual crystalline WO₃ will remain. The maximum monolayer dispersion (threshold) is 0.21 g and 0.20 g WO₃/100 m² γ-Al₃O₃ by XRD and XPS respectively. It agrees with the value (0.189 g WO₃/100 m² or 4.90 × 10^?18 W atoms/m²) calculated from the model on assumption that the WO₃ is dispersed as a closed-packed monolayer on γ-Al₂O₃ surface. Inasmuch as WO₃/γ-Al₂O₃ system is stable up to higher temperature, e.g. 700°C, than MoO₃/γ-Al₂O₃ system, WO₃ seems unfavorable to form new bulk compound with γ-Al₂O₃ at that temperature. However, Al₂(MoO₄)₃ forms perceptibly in MoO₃/γ-Al₂O₃ system at 500°C. Besides, the size of residual crystalline WO₃ in WO₃/γ-Al₂O₃ is much smaller than that of MoO₃ in MoO₃/γ-Al₂O₃. It might be the reason that WO₃/γ-Al₂O₃ catalyst is superior to MoO₃/γ-Al₂O₃ in hydrodesulfurization (HDS) or hydrodenitrogenation (HDN) in some cases.     

Vanadium (III), oxovanadium (IV) and oxovanadium (V) trifluoro-methanesulfonates

V(SO₃CF₃)₃, VO(SO₃CF₃)₂ and VO(SO₃CF₃)₃ have been prepared by reacting V(O₂CCF₃)₃, VO(O₂CCF₃)₂ and VOC1₃ with HSO₃CF₃. The i.r. data suggest a bridging bidentate nature for SO₃CF₃ groups. The diffuse reflectance spectrum of V(SO₃CF₃)₃ suggests hexacoordination of vanadium, whilst that of VO(SO₃CF₃)₂ is comparable to either five or six coordinated oxovanadium (IV) systems. The magnetic moments of V(SO₃CF₃)₃ and VO(SO₃CF₃)₂ are slightly lower than the spin-only values. Thermal decomposition of these triflates is simple. All the three triflates form coordination complexes with pyridine, 2, 2′-bipyridyl and triphenylphosphine oxide.     

Synthese und Strukturen neuer Ringverbindungen des Bismuts mit Tris(trimethylsilyl)silyl und ‐stannylresten – [(Me3Si)3Si]4Bi4 und [(Me3Si)3Sn]6Bi8

Synthesis and Structures of Novel Ring Compounds of Bismuth with Tris(trimethylsilyl)silyl and ‐stannyl Substituents – [(Me₃Si)₃Si]₄Bi₄ and [(Me₃Si)₃Sn]₆Bi₈ A bicyclo[3.3.0]octane‐like core consisting of eight bismuth atoms is found in the novel octabismuthane Bi₈[Sn(SiMe₃)₃]₆. It is prepared like Bi₄[Si(SiMe₃)₃]₄ by reduction of BiBr₃ with Li(thf)₃E(SiMe₃)₃ (E = Si, Sn) together with (Me₃Si)₆E₂. Both bismuth ring compounds have been characterized by single crystal X‐ray crystallography.     

Synthesis of cationic dialkylgold(III) complexes: nature of the facile reductive elimination of alkane

A series of gold(III) cations of the type cis-[CH₃)₂AuL₂]⁺ X^? where L  Ph₃, PMePh₂, PMe₂Ph, PMe₃, AsPh₃, AsPh₃, SbPh₃, $\text{1}\text{2}$H₂NCH₂CH₂NH₂, $\text{1}\text{2}$ Ph₂PCH₂CH₂-PPh₂, $\text{1}\text{2}$ Ph₂AsCH₂CH₂AsPh₂, and $\text{1}\text{2}$o-C₆H₄(AsMe₂)₂ and X  BF₄^?, PF₆^?, ClO₄^?, and F₃CSO₃^? has been prepared. In addition, the cis complexes [(CH₃)(CD₃)-Au(PPh₃)₂]F₃CSO₃, [(C₂H₅)₂Au(PPh₃)₂]F₃CSO and [(n-C₄H₉)₂Au(PPh₃)₂]F₃-CSO₃ have been synthesized. All have been characterized by PMR, Raman and infrared spectroscopy. These [R₂AuL₂]X compounds yield only ethane, butane, or octane via reductive elimination, and no disproportionation is observed. The alkane eliminations have been studied in CHCl₃, CH₃Cl₂, and CH₃COCH₃ solution as a function of temperature, concentration of the complex, and concentration of added ligand L. Elimination is fastest when L is bulky (PPh₃ > PMePh₂ > PMe₂Ph > PMe₃), decreases in the sequence SbPh₃ > AsPh₃ > PPh₃, is slow with chelating ligands, is inhibited by excess ligand, and there is small anion effect as X is varied. As R is varied, the rate of elimination decreases Bu ? Et > Me. An intramolecular dissociative mechanism is proposed which involves rapid elimination of alkane from an electron deficient dialkylgold(III) complex with nonequivalent gold—carbon bonds and produces the corresponding [AuL₂]X complex.     

Synthese,Eigenschaften und Struktur von cis-Dihydridoazido-tris(triphenylphosphino)-iridium

Synthesis, Properties, and Structure of cis-Dihydrido Azido Tris(triphenylphosphino) Iridium cis-IrH₂(N₃)(PPh₃)₃ is formed from IrCl₃(PPh₃)₃ and NaN₃ in alcohol. The solvent transfers the hydride ions whereby aldehyde is formed. The creme-colored cis-IrH₂(N₃)(PPh₃)₃ is a diamagnetic low-spin complex. Exposure to light yields H₂ and Ir(N₃)(PPh₃)₃ in a reversible process. The cis position of the hydrido ligands is confirmed by the i.r. and H-N.M.R. spectra. Cis-IrH₂(N₃)(PPh₃)₃ crystallizes in the monoclinic system with the space group P2₁/c. The crystal structure exhibits isolated octahedral complexes, in which one hydrido ligand is located trans to the azido group. The other one being trans to one of the phosphine ligands.     

Cyclothiazeno-Komplexe des Wolframs mit Phosphaniminatound tertiär-Butoxyliganden

Cyclothiazeno Complexes of Tungsten with Phosphoraneiminato and t-Butoxy Ligands The cyclothiazeno complex [WCl₃(N₃S₂)]₂ reacts with the silylated phosphaneimine Me₃SiNPPh₃ in THF solution forming the cyclothiazenophosphoraneiminato complex [Cl₂W(N₃S₂)(NPPh₃)]_n which forms green crystals of [Cl₂W(N₃S₂)(NPPh₃)(Py)] ( 1 ) when pyridine is added. The corresponding reaction with Me₃SiNPMe₃ leads to the methyl derivative which is analogous to 1 and which is obtained as dark green crystals along with the tetrakis(phosphoraneiminato) complex of the crystal composition [W(NPMe₃)₄]Cl₂ · 2 [Cl₂W(N₃S₂)(NPMe₃)(Py)] · 2 CH₂Cl₂ ( 2 ). According to the crystal structure analyses the phosphoraneiminato ligands NPR₃^– cause as a result of the short WN bonds of approximately 180 pm a strong trans influence on one of the WN bonds of the planar WN₃S₂ rings and alternatingly long SN bonds. With LiOCMe₃ [WCl₃(N₃S₂)]₂ reacts forming the centrosymmetrically dimeric cyclothiazeno alkoxy complex [(Me₃CO)₄W(N₃S₂)Li₂Cl]₂ ( 3 ) the ion ensemble of which is linked via the lithium and the chlorine atoms.     

Bulky Phenyl Modifications of the Silanide Ligand Si(SiMe3)3 – Synthesis and Reactivity

The synthesis and structural characterization of bulkier variations of the very common organometallic compound MSi(SiMe₃)₃, namely MSi(SiMe₃)(SiPh₃)₂ 3 and MSi(SiPh₃)₃ [M = Li ( 1 ), K ( 5 )] are presented, which can be synthesized via a step by step exchange of SiMe₃ groups by bulkier SiPh₃ groups. This synthetic route is high selective and is performed in good yields via the silanes Si(SiMe₃)₂(SiPh₃)₂ ( 2 ) and Si(SiMe₃)(SiPh₃)₃ ( 4 ). Additionally, the corresponding silanes HSi(SiMe₃)(SiPh₃)₂ ( 6_H ) and HSi(SiPh₃)₃ ( 7_H ) are obtained via the reaction of 3 and 5 with aqueous HCl, respectively. Oxidation of 6_H with CCl₄ gives the chlorsilane Cl‐Si(SiMe₃)(SiPh₃)₂ ( 6_Cl ). The bulkiest chlorsilane Cl–Si(SiPh₃)₃ ( 7 ) is obtained by the reaction of 5 with ECl₂ (E = Sn, Pb).     

Zur präparativen Bildung des Tri-tert.-butyl-nonaphosphans(3); P9(CMe3)3

Formation of Tri-tert.-butyl-nonaphosphane (3); P₉(CMe₃)₃ P₉(CMe₃)₃ 1 is formed by the reaction of “Na₃P/K₃P” with (Me₃C)PCl₂ [maximum yield 20% with regard to (Me₃C)PCl₂]. The molar ratio of the reactants used on this synthesis is Na/K:P₄:(Me₃C)PCl₂ is 4:1:2. The method of preparation is described.     

Reassignment of the infrared spectra of SnPh3Cl. An infrared method to characterize SnPh3Cl 1—1 adducts

The stretching vibrations of the SnC₃Cl group in the infrared spectrum of SnPh₃Cl have been reassigned on the basis of an SnC₃ group belonging to the C_3ν point group which is replaced by D_3h in SnPh₃Cl₂TMN (TMN = tetramethylammonium). The important shift (108 cm⁻¹) of ν_sSnC₃ from SnPh₃Cl to SnPh₃Cl₂ TMN is due to a “C_3ν point group inversion” (ν_sSnC₃ is higher in frequency than ν_asSnC₃ in the i.r. spectrum of SnPh₃Cl).     

MnS-Ln2S3 (Ln = La, Nd, or Gd) phase diagrams; thermodynamics of phase transitions

The MnS-La₂S₃ phase diagram has been constructed where the incongruently melting compound Mn₂La₆S₁₁ is formed. Complex sulfide Mn₂La₆S₁₁ is characterized by monoclinic structure; its incongruent melting temperature is 1535 K. Eutectic coordinates are 31 mol % La₂S₃, 1490 K. The extent of the ??-La₂S₃ based solid solutions at 1570 K is 8 mol % MnS; at 770 K, ??-La₂S₃ dissolves 3 mol % MnS. The MnS-Gd₂S₃ system is a eutectic with limited solid solutions. Eutectic coordinates are 35.5 mol % Gd₂S₃, 1640 K. Solubility in ??-Gd₂S₃ is 28 mol % MnS at 1570 K, in ??-Gd₂S₃ is 13 mol % MnS at 1170 K, and in MnS is 1 mol % Gd₂S₃. Thermochemical equations have been composed for eutectic and eutectoid phase transformations. A MnS-Nd₂S₃ phase diagram has been predicted.     

Theoretical Studies of Inorganic Compounds. 361) Structures and Bonding Analyses of Beryllium Chloro Complexes with Nitrogen Donors

Quantum chemical calculations at various levels of theory (BP86, B3LYP, MP2, CCSD(T), CBS‐QB3) of the beryllium complexes [BeCl₂(NHPH₃)], [BeCl₂(NHPH₃)₂], [BeCl₃(py)]^?, [BeCl₂(NH₃)], [BeCl₂(NH₃)₂], [BeCl₃(py)]^? and [BeCl₃(NH₃)]^? as well as the boron compounds [BCl₃(py)] and [BCl₃(NH₃)] show that BeCl₂ is a very strong Lewis acid. The theoretically predicted bond dissociation energy at CBS‐QB3 of Cl₂Be‐NH₃ (D_e = 32.5 kcal/mol)is even higher than that of Cl₃B‐NH₃ (D_e = 28.6 kcal/mol). Even the second ammonia molecule in [BeCl₂(NH₃)₂] still has a strong bond with D_e = 24.2 kcal/mol. The theoretically predicted bond strengths for the phosphaneimine ligands in [BeCl₂(NHPH₃)₂] are D_e = 46.7 kcal/mol for the first ligand and D_e = 29.8 kcal/mol for the second. The anion BeCl₃^? is a moderately strong Lewis acid which has bond energies of D_e = 14.1 kcal/mol in [BeCl₃(py)]^? and D_e = 14.2 kcal/mol in [BeCl₃(NH₃)]^?. The higher bond energy of [BeCl₂(NH₃)] compared with [BCl₃(NH₃)] comes from less deformation energy for BeCl₂ than for BCl₃. The intrinsic attraction between BeCl₂ and NH₃ calculated with frozen geometries of the complex geometry is ～5 kcal/mol less than the attraction between BCl₃ and NH₃. The bonding analysis with the EDA method shows that the attractive energy of the beryllium complexes comes manly from electrostatic attraction. The larger contribution of the electrostatic term is the most significant difference between the nature of the donor‐acceptor bonds of the beryllium and boron complexes.     

Diphenyl-bis(P-trimethylphosphinimino)-phosphoniumchlorid

Diphenyl-bis(P-trimethylphosphinimino)-phosphonium Chloride The reaction of Na⊕(CH₃)₃Si? N? P(C₆H₅)₂? N? Si(CH₃)₃? III with (CH₃)₃PCI₂ results in the elimination of NaCI and (CH₃)₃SiCI and the formation of (CH₃)₃P = N? P(C₆H₅)₂? N = P(CH₃)₃ ⊕CI? VII . The mechanism of the reaction is discussed. (CH₃)₃P = N? P(C₆H₅)₂ = N? Si(CH₃)₃ V can be obtained as an intermediate. This intermediate, when synthesized by an other independent route, is found to react with (CH₃)₃PCI₂ to give the same product VII .     

[(Ph3Sn)3VO4]·CH3CN und [(Ph3Sn)3VO4]·2 DMF,Triphenylzinnvanadate mit neuartigen Kettenstrukturen

[(Ph₃Sn)₃VO₄]·CH₃CN and [(Ph₃Sn)₃VO₄]·2 DMF, Triphenyltin Vanadates with Novel Chain Structures The reaction of Na₃VO₄ with Ph₃SnCl in a water/CH₂Cl₂ mixture leads to the formation of [(Ph₃Sn)₃VO₄] ( 1 ). Recrystallization of 1 from toluene/CH₃CN gives pale yellow crystals of [(Ph₃Sn)₃VO₄]·CH₃CN ( 2 ). 2 crystallizes as coordination polymer which consists of infinite chains composed of corner‐sharing VO₄ tetrahedra and Ph₃SnO₂ trigonal bipyramides. Additionally the VO₄ groups are connected to two terminal SnPh₃‐Groups containing tin atoms in a tetrahedral environment. [(Ph₃Sn)₃VO₄]·2 DMF ( 3 ) which is obtained from Na₃VO₄ and Ph₃SnCl in a water/DMF mixture contains a polymeric chain structure similar to 2 and additionally one of the terminal SnPh₃ groups is coordinated to a DMF solvent molecule.     

Solubilities of lanthanum oxide in fluoride melts: Part I. Solubility in M3AlF6 (M = Li, Na, K)

Solubility of lanthanum oxide was measured by thermal analysis. The solubility in alkali cryolites is rather high, because of chemical reactions between lanthanum oxide and cryolites. In Li₃AlF₆-La₂O₃, alumina precipitates, in the other systems the mixed oxide LaAlO₃ is formed. In La₂O₃-Li₃AlF₆ the eutectic point is at 9.5 mol% La₂O₃ and 755 °C. The eutectic points in La₂O₃-Na₃AlF₆ and La₂O₃-K₃AlF₆ are at 11.5 mol% La₂O₃, and at 937 and 934 °C, respectively.     

A PHOSPHORUS-31 NUCLEAR MAGNETIC RESONANCE STUDY OF TERTIARY PHOSPHINE DERIVATIVES OF GROUP VI METAL CARBONYLS. IV. SUBSTITUTED TRIARYLPHOSPHINES

Abstract

Thirty compounds of the type (ZC₆H₄)₃PM(CO)₅ where Z is 3-CH₃, 4-CH₃, 3-CH₃O, 4-CH₃O, 3-CF₃, 4-CF₃, 4-Cl, 4-F, 4-CH₃S, or 4-(CH₃) C and M is Cr, Mo, or W are reported, in addition to [4-(CH₃)₃SiC₆H₄]₃ PW(CO)₅ and [(2-CH₃C₆H₄)n(C₆H₅)3–n P] M(CO)₅ where n is 1 or 2 and M is Cr, Mo, or W. Phosphorus-31 NMR and infrared data are presented. In general, the compounds containing the more effective electron withdrawing substituents on the tertiary arylphosphines exhibit the larger ³¹P coordination chemical shifts, the higher carbonyl stretching frequencies, and the larger phosphorus-31-tungsten-183 coupling constants.     

F3SiSH and (F3Si)2S: Conflicting Observations Resolved by Unambiguous Syntheses

The reaction between liquid F₃SiI and red HgS mainly yields the disilylsulfane (F₃Si)₂S and, in smaller amounts, hitherto unknown (F₃SiS)₂SiF₂. These fluorosilylsulfanes have different thermal stabilities. (F₃Si)₂S is a versatile precursor for F₃Si derivatives, and at ambient temperature it is stable, while (F₃SiS)₂SiF₂ decomposes rapidly. F₃SiSH has been obtained, along with F₃SiBr, by selective cleavage of one of the Si–S bonds in (F₃Si)₂S with HBr in the liquid phase and was for the first time unambiguously characterized. Contrary to previous reports, (F₃Si)₂O rather than (F₂SiS)₂ is formed when SiF₄ is passed over SiS₂ at 1298 K in a quartz tube. Raman and infrared spectra of (F₃Si)₂S, F₃SiSH and its deuterated derivative F₃SiSD have been measured and assigned to vibrational fundamentals. Multinuclear NMR spectra have been recorded.