Intramolecular rearrangement of organosilyl groups between oxygen and nitrogen in aminosiloxanes - a joint experimental-theoretical study, part II

Lithium amino-di-tert-butylsilanolate reacts with halosilanes to give 1-silylamino-1,3-siloxanes (1-7). The tetrakis(1-silylamino)siloxane thermally condenses yielding a spirocyclic six-membered ring (8). One six-membered ring of 8 forms a boat and the other has a twist conformation. Lithium salts of amino-disiloxanes form silylamino-silanolates or amido-disiloxanes. The first includes a 1,3-silyl group migration from the oxygen to the nitrogen atom. The energies of the isomeric lithium salts of model compounds are calculated and show that the lithium-trimethylsilylamino-dimethylsilanolate III is 0.7 kcal/mol more stable than the isomeric lithium-1,3-disiloxaneamide V. Experiments show that the lithium salts of amino-1,3-disiloxanes, (Me₃C)₂SiNH₂-O-R (R = SiMe₃, SiMe₂Ph, SiF₂CMe₃) reacts with ClSiMe₃, FSiMe₂Ph or F₃SiCMe₃ under a 1,3-O-N-silyl group migration to give the 1-silylamino-1,3-disiloxanes 9-11. If the trimethylsilyl group is substituted by SiMeF₂, the difference between the isomers III′ and V′ is even smaller, 0.12 kcal/mol, and the barrier to reaction via the dyotropic transition state is calculated to be 10.1 kcal/mol. Interestingly, the fluorine atoms allow for two other isomers VI and VIII which are even lower in energy. The low difference in the energies of III and V respectively VI and VIII explains that in absence of steric and/or electronic restraints the lithium salts of amino-1,3-disiloxanes react halosilanes to give both isomeric silylamino-1,3-disiloxanes, e. g. the lithiated (Me₃C)₂SiNH₂-O-SiF₂CMe₃ reacts with F₂SiMe₂ or F₃SiPh to give the structural isomers 12, 13, and 14, 15.The silyl group migration can be prevented kinetically, e. g. the lithium salts of (Me₃C)₂SiNH₂-O-R (R = SiF(N(CHMe₂)₂)₂, SiH(CMe₃)₂) react with F₂SiMe₂ or F₂Si(CMe₃)₂ to 16 and 17. A thermodynamically prevented rearrangement is observed in the reaction of lithiated (Me₃C)₂SiNH₂-O-SiMe₃ with F₃SiR (R = CMe₃ (18), Ph (19), N(SiMe₃)₂ (20), C₆H₂ (CMe₃)₃ (21). 18-21 ((Me₃C)₂SiNHSiF₂R)-O-SiMe₃) are formed.LiF-elimination from (Me₃C)₂SiNHLiO-SiF₂Me leads to the formation of the eight-membered (SiOSiN)-ring 22. The most stable lithium salts of 1-silylamino-1,3-disiloxanes form amides. This explains that in further reactions with halosilanes, the new ligand is bonded with the nitrogen atom (28-30). In results of crystal structure determinations new lithium-1-fluorosilylamino-1,3-disiloxanes of 20, (21, 23-25) are presented. 23 crystallizes as tricyclic, 24 as an unknown pentacyclic, and 25, as monomeric compound. In 25 the shortest Si-N bond length (157.9 pm) with four coordinate silicon is found. Lithium salts of 1-fluorosilylamido-1,3-disiloxanes lose thermally LiF with formation of siloxane substituted cyclodisilazanes, 26 and 27. Crystal structures of 4, 8, 17, 20, 21, 22, 23, 24, 25, 26, 28 are presented.     

Palladium(II)?NHC complexes containing benzimidazole ligand as a catalyst for C?N bond formation

The reaction of 2‐(2‐bromoethyl)‐1,3‐dioxane with 1‐alkylbenzimidazole derivatives results in the formation of the new benzimidazolium salts (1). The reaction of Pd(OAc)₂ with 1,3‐dialkylbenzimidazolium salts (1a–c) yields palladium N‐heterocyclic carbene (NHC) complexes (2a–c). All synthesized compounds were characterized by ¹H NMR, ¹³ C NMR, IR and elemental analysis techniques which support the proposed structures. As catalysts, these new palladium complexes offer a simple and efficient methodology for the synthesis of triarylamines and secondary amines from anilines and amines and in a single step with potassium tertiary butoxide as a base. Copyright © 2010 John Wiley & Sons, Ltd.     

Dynamics of lithium electrode passivation in aprotic organic electrolytes,studied by electrochemical noise method

Lithium electrode passivation is studied in different organic electrolytes, namely, 1 M LiClO₄ in 1,3-dioxolane, 1 M LiN(CF₃SO₂)₂ in 1,3-dioxolane, 1 M LiPF₆ in an ethylene carbonate-diethyl carbonate mixture, 1 M LiPF₆ in an ethylene carbonate-dimethyl carbonate mixture, using the electrochemical noise method. The dynamics of passive film formation on the lithium surface in the mentioned electrolytes that differ in their corrosivity towards lithium is followed.     

Reactivity of a Tetra(o‐tolyl)diborane(4) Dianion as a Diarylboryl Anion Equivalent

Lithium and magnesium salts of tetra(o‐tolyl)diborane(4) dianion, having B=B double bond character, were synthesized. It was clarified that the lithium salt of the dianion has a high‐lying HOMO and a narrow HOMO–LUMO gap, which were perturbed by dissociation of Li⁺ cation, as judged by UV/Vis spectroscopy and DFT calculations. The lithium salt of the dianion reacted as two equivalents of a diarylboryl anion with CH₂Cl₂ or S₈ to give boryl‐substituted products.     

Phosphoryl‐Rich Flame‐Retardant Ions (FRIONs): Towards Safer Lithium‐Ion Batteries

The functionalized catecholate, tetraethyl (2,3‐dihydroxy‐1,4‐phenylene)bis(phosphonate) (H₂‐DPC), has been used to prepare a series of lithium salts Li[B(DPC)(oxalato)], Li[B(DPC)₂], Li[B(DPC)F₂], and Li[P(DPC)₃]. The phosphoryl‐rich character of these anions was designed to impart flame‐retardant properties for their use as potential flame‐retardant ions (FRIONs), additives, or replacements for other lithium salts for safer lithium‐ion batteries. The new materials were fully characterized, and the single‐crystal structures of Li[B(DPC)(oxalato)] and Li[P(DPC)₃] have been determined. Thermogravimetric analysis of the four lithium salts show that they are thermally stable up to around 200 °C. Pyrolysis combustion flow calorimetry reveals that these salts produce high char yields upon combustion.     

Preparation and Characterization of N,N′-Dialkyl-1,3-propanedialdiminium Chlorides,N,N′-Dialkyl-1,3-propanedialdimines,and Lithium N,N′-Dialkyl-1,3-propanedialdiminates

We describe convenient preparations of N,N′-dialkyl-1,3-propanedialdiminium chlorides, N,N′-dialkyl-1,3-propanedialdimines, and lithium N,N′-dialkyl-1,3-propanedialdiminates in which the alkyl groups are methyl, ethyl, isopropyl, or tert-butyl. For the dialdiminium salts, the N₂C₃ backbone is always in the trans-s-trans configuration. Three isomers are present in solution except for the tert-butyl compound, for which only two isomers are present; increasing the steric bulk of the N-alkyl substituents shifts the equilibrium away from the (Z,Z) isomer in favor of the (E,Z), and (E,E) isomers. For the neutral dialdimines, crystal structures show that the methyl and isopropyl compounds adopt the (E,Z) form, whereas the tert-butyl compound is in the (E,E) form. In aprotic solvents all four dialdimines (as well as the lithium dialdiminate salts) adopt cis-s-cis conformations in which there presumably is either an intramolecular hydrogen bond (or a lithium cation) between the two nitrogen atoms.     

微波辐射下合成3-芳基-9-氨基-1,2,3,4-四氢吖啶-1-酮衍生物

在微波辐射和对甲基苯磺酸的催化作用下, 5-芳基-1,3-环己二酮与邻氨基苯甲腈进行缩合反应, 得到了N-取代的2-氨基苯甲腈衍生物, 在K₂CO₃和Cu₂Cl₂的催化作用下进一步合环, 得到3-芳基-9-氨基-1,2,3,4-四氢吖啶-1-酮衍生物, 用LiAlH₄还原羰基得到3-芳基-9-氨基-1,2,3,4-四氢吖啶-1-醇衍生物. 新合成化合物的结构均经元素分析、红外光谱和核磁共振光谱予以确认.     

Apparent Molar Volume, Heat Capacity, and Conductance of Lithium Bis(trifluoromethylsulfone)imide in Glymes and Other Aprotic Solvents

Lithium bis(trifluoromethylsulfone)imide (LiTFSI) is a promising electrolyte for high-energy lithium batteries due to its high solubility in most solvents and electrochemical stability. To characterize this electrolyte in solution, its conductance and apparent molar volume and heat capacity were measured over a wide range of concentration in glymes, tetraethylsulfamide (TESA), acetonitrile, -butyrolactone, and propylene carbonate at 25°C and were compared with those of LiClO₄ in the same solvents. The glymes or n(ethylene glycol) dimethyl ethers (nEGDME), which have the chemical structure CH₃–O–(CH₂–CH₂–O) _n –CH₃ for n = 1 to 4, are particularly interesting since they are electrochemically stable, have a good redox window, and are analogs of the polyethylene oxides used in polymer-electrolyte batteries. TESA is a good plasticizer for polymer-electrolyte batteries. Whenever required, the following properties of the pure solvents were measured: compressibilities, expansibilities, temperature and pressure dependences of the dielectric constant, acceptor number, and donor number. These data were used in particular to calculate the limiting Debye-Hückel parameters for volumes and heat capacities. The infinite dilution properties of LiTFSI are quite similar to those of other lithium salts. At low concentrations, LiTFSI is strongly associated in the glymes and moderately associated in TESA. At intermediate concentrations, the thermodynamic data suggests that a stable solvate of LiTFSI in EGDME exists in the solution state. At high concentrations, the thermodynamic properties of the two lithium salts approach those of the molten salts. These salts have a reasonably high specific conductivity in most of the solvents. This suggests that the conductance of ions at high concentration in solvents of low dielectric constant is due to a charge transfer process rather than to the migration of free ions.     

A Simple Route to New N(3)-Substituted 5-Aryl-2-(dialkylamino)-1,3-oxazolium Salts and N(1)-Substituted 4-Aryl-2-(dialkylamino)-1H-imidazoles

In the reaction of N,N-dialkyl-dichloromethaniminium chlorides 11 with 2-aminoacetophenones 12 , a general and simple route to heretofore unknown 5-aryl-substituted 2-(dialkylamino)-1,3-oxazolium salts 13 and 5-aryl-substituted 2-(dialkylamino)oxazoles 14 was found. From the 2-(dialkylamino)-1,3-oxazoles 14 , the corresponding oxazolium salts 13 were obtained after alkylation with (MeO)₂SO₂. The new oxazolium salts 13 were converted to 1-substituted 4-aryl-2-(dialkylamino)-1H-imidazoles 9 by treatment with NH₄OAc. The possible use of these 1H-imidazoles as dye educts was explored. Analytical data, as well as AM1 calculations, reveal some remarkable differences between the structures of the neutral imidazoles 9 and their positively charged oxazolium precursors 13 .     

Funktionelle Siloxane und Cyclotetrasiloxane – Kristallstruktur eines Cycloboratrisiloxans

Functional Siloxanes and Cyclotetrasiloxanes – Molecular Structure of a Cycloboratrisiloxane Lithium salts of di-tert-butyl-fluorosilanol and -silandiol react with fluorosilanes to give 1,3-di- ( 1 , 2 ), 1,3,5-tri- ( 3 , 4 ), and 1,3,5,7,9-pentasiloxanes ( 5 ). Reactions of the dilithium salt of the silandiol with SiF₄ and CH₃SiF₃ lead to the formation of fluorofunctional cyclo-1,3,5,7-tetrasiloxanes ( 6 , 7 ). The cyclotetra-siloxane 8 is obtained by thermal LiF elimination from 1,1-difluoro-1,3-disiloxane-3-ol ( 2 ). The eight-membered ring systems 9 and 10 are formed in the reaction of dilithiated 1,3,5-trisiloxane-1,5-diol with SiF₄ ( 9 ) and BF₃ ( 10 ). The crystal structure of the cyclo-1-bora-3,5,7-trisiloxane 10 is reported and discussed.     

Die Kristallstrukturen der Monohydrate von Lithiumchlorid und Lithiumbromid

Crystal Structure of the Monohydrates of Lithium Chloride and Lithium Bromide Using single crystal analysis and powder diffraction data the crystal structures of the monohydrates of lithium chloride and lithium bromide were solved. Both compounds crystallise isotypic in the space group Cmcm (LiCl·H₂O: single crystal analysis; T = 100 K; a = 758, 35(2); b = 768, 07(2); c = 762, 35(2) pm; Z = 8; 1179 unique reflections; R₁ = 0, 0196. LiBr·H₂O: Rietveld‐refinement; T = 220 K; a = 806, 15(1); b = 799, 44(1) und c = 794, 61(1) pm; Z = 8; 157 unique reflections; R_p = 0, 0922; R_wp = 0, 0979; R_exp = 0, 0657). The structure derives from the perowskite structure according to the formula X(H₂O)Li□₂ (X = Cl, Br). The orientation of the water molecules is linked clearly to the distribution of the lithium cations and vice versa. The high level ionic conductivity in the cubic high temperature phase of LiBr·H₂O is related to the initial rotation of the water molecules during the phase transformation. This motion favours the lithium ion hopping and the melting of the lithium substructure respectively.     

The Formation of Surface Lithium–Iron Ternary Hydride and its Function on Catalytic Ammonia Synthesis at Low Temperatures

Lithium hydride (LiH) has a strong effect on iron leading to an approximately 3 orders of magnitude increase in catalytic ammonia synthesis. The existence of lithium–iron ternary hydride species at the surface/interface of the catalyst were identified and characterized for the first time by gas‐phase optical spectroscopy coupled with mass spectrometry and quantum chemical calculations. The ternary hydride species may serve as centers that readily activate and hydrogenate dinitrogen, forming Fe‐(NH₂)‐Li and LiNH₂ moieties—possibly through a redox reaction of dinitrogen and hydridic hydrogen (LiH) that is mediated by iron—showing distinct differences from ammonia formation mediated by conventional iron or ruthenium‐based catalysts. Hydrogen‐associated activation and conversion of dinitrogen are discussed.     

The synthesis and characterization of some new vic-dioximes and their transition metal complexes

In this study, three new vic-dioximes, [L¹H₂], N-(5-chloro-2-methoxyphenyl)amino-1-acetyl-1-yclohexenylglyoxime, [L²H₂],N-(3-chloro-4-methoxyphenyl)amino-1-acetyl-1-cyclohexenylgly-oxime and [L³H₂], N-(3-chloro-2-methoxyphenyl)amino-1-acetyl-1-cyclohexenylglyoxime were synthesized from 1-acetyl-1-cyclohexeneglyoxime and the corresponding substituted aromatic amines. Metal complexes of these ligands were also synthesized with Ni(II), Cu(II) and Co(II) salts. The structures of these new compounds (ligands and complexes) were characterized with FT-IR, magnetic susceptibility measurement, molar conductivity measurements, mass spectrophotometer measurements, thermal methods (TGA), ¹H NMR and ¹³C NMR spectral data and elemental analyses.     

Two Energetic Ionic Salts of en·PA·H2O and en·TNR: Preparation,Structural Characterization,and Properties

Energetic salts of en · PA · H₂O and en · TNR were synthesized by using ethylenediamine and picric acid (PA) or 2,4,6‐trinitroresorcinol (TNR) as raw materials, and their structures were characterized by elemental analysis and FT‐IR spectroscopy. Single crystals of the title salts were obtained and their structures were determined by single‐crystal X‐ray diffraction. The thermal decomposition behaviors were investigated by DSC and TG‐DTG technologies, furthermore the non‐isothermal kinetic parameters and enthalpies of formation for the salts were calculated. Their combustion heats were measured by oxygen bomb calorimetry and their enthalpies of formation were also calculated based on the combustion heat data. In addition, the detonation pressure (P) and detonation velocities (D) of the salts were predicted by using the K‐J equations. The results indicated that the title salts have potential applications in the field of energetic materials.     

Mixed fluoroamine complexes of chromium(III)

Summary Mixed difluoro(diamine)(diamme)chromium(III) complexes have been synthesized with ethylenediamine (en), 1,3 propanediamine(tn) and 1,2-cyclohexanediamine(chxn):trans-[CrF₂(aa)(bb)]Br (aa=en, bb=tn; aa=tn, bb= chxn) andcis-[CrF₂(aa)(bb)]Br (aa=en, bb=chxn). The corresponding fluoroaqua(diamine) (diamine)chromium(III) complexes have been prepared by acid hydrolysis as perchlorate or iodide salts. All have been characterized by chemical analysis, electronic and i.r. spectra and conductivity measurements.     

2,2,4,4-Tetramethyl-2,4-disila-cyclo-butylzinkchlorid · TMEDA und verwandte Verbindungen

2,2,4,4-Tetramethyl-2,4-disila-cyclo-butylzinc Chloride · TMEDA and Related Compounds The reaction of (tmeda)lithium 2,2,4,4-tetramethyl-2,4-disila-cyclo-butanide with anhydrous zinc(II) chloride in pentane in the molar ratio of 2:1 does not yield the expected dialkylzinc derivative but the monosubstitution product 2,2,4,4-Tetramethyl-2,4-disila-cyclo-butylzinc chloride · tmeda 1 . This derivative crystallizes in the orthorhombic space group Pnma with a = 1 235.0(1); b = 1 696.8(2); c = 1 148.0(1) pm and Z = 4. The Zn? C bond lengths lie with 198,4 pm in the characteristic region for compounds containing a tetrahedrally coordinated zinc atom. The thermolysis of 1 leads under elimination of ZnCl₂ to the formation of Bis(2,2,4,4-tetramethyl-2,4-disila-cyclo-butyl)zinc · tmeda 2 . (tmeda)LiCH(SiMe₃)₂ reacts analogously with one equivalent of ZnCl₂ to Bis(trimethylsilyl)methylzinc chloride · tmeda 3 . Lithium methanide or Lithium butanide add to a Si-C bond of 1,1,3,3-tetramethyl-1,3-disila-cyclo-butane, and these acyclic lithium alkanides 4 ( a : R = Me, b : R = n-Bu) yield with zinc(II) chloride the destillable dialkyl zinc compounds Bis(2,2,4,4-tetramethyl-2,4-disilapentyl)- 5 a and Bis(2,2,4,4-tetramethyl-2,4-disila-octyl)zinc 5 b .     

Anionic polymerization of methacrylate monomers initiated by lithium dialkylamides

The anionic polymerization of methacrylate monomers has been investigated with lithium dialkylamides as initiators in THF and toluene, respectively. Theoretical arguments and previous studies of mixed aggregates of lithiated organic compounds support the complexity of these systems. Lithium diisopropylamide (LDA) shows the highest initiation efficiency (e.g., f = 75% in THF at −78°C). Interestingly enough, lithium chloride has a remarkable beneficial effect on the methacrylates polymerization in THF at −78°C, due to the formation of 1 : 1 mixed dimer with LDA, which promotes a well-controlled anionic polymerization (M_w/M_n = 1.05) with a high initiation efficiency (94%). The less bulky lithium–diethylamide (LDEA) is much less efficient (f = 26%), essentially as a result of some associated “dormant” species and side reactions on the carbonyl group of MMA. Although various types of ligands have been screened, no remarkable improvement of LDEA efficiency has been observed. Lithium bis(trimethylsilyl)amide (LTMSA) has also been used to increase the steric hindrance of the initiator. This compound is, however, unable to initiate the methacrylates polymerization, more likely because of a too low basicity and a too strong Li—N bond. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3637–3644, 1997     

Structure and properties of lithium n-butyl amidinates

Lithium n-butyl amidinates (formally lithium salts of N',N-disubstituted amidoimides of pentanoic acid) with various substituents were prepared and characterized in solution by ¹H, ⁷Li, ¹³C and ¹⁵N NMR spectra parameters in C₆D₆, THF-d₈ and Et₂O-d₁₀. The characteristic spectral parameters were compared with parent carbodiimides and amidines prepared by hydrolysis, where large solvent effects were described. Five of studied compounds were studied by X-ray diffraction techniques in the solid state. Lithium n-butyl amidinates containing less bulky substituents like isopropyl or cyclohexyl crystallize with Et₂O or THF as centrosymmetric dimers with mutually parallel amidinate moieties. The lithium N,N'-bis[2,6-di(propan-2-yl)phenyl]n-butylamidinate crystallizes from Et₂O solution as an asymmetric dimer. The first unit is composed by one ligand coordinated to one of lithium atoms. The lithium atom is also coordinated by one of the nitrogen atoms of the second ligand. The second nitrogen atom of the same ligand is coordinated to the second lithium atom which is also connected to the Et₂O molecule and the aromatic ring of the ligand in a η³-fashion. The same compound crystallizes from the THF solution as a monomeric bis-tetrahydrofuranate.     

New molecular magnetic metals: κ-(BDH-TTP)4CuCl4·(H2O)n and κ-(BDH-TTP)2[CuCl4]0.67·(H2O)0.33 (BDH-TTP is 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene)

New radical cation salts based on 2,5-bis(1,3-dithiolan-2-ylidene)-1,3,4,6-tetrathiapentalene (BDH-TTP), viz., κ-(BDH-TTP)₄CuCl₄·(H₂O) _n (1) and κ-(BDH-TTP)₂[CuCl₄]_0.67· ·(H₂O)_0.33 (2), were synthesized and structurally characterized. Single crystals were prepared by the electrochemical oxidation of BDH-TTP under galvanostatic conditions. The X-ray diffraction study showed that the salts have layered structures characterized by the presence of κ-type BDH-TTP conducting layers. These layers alternate with the complex anions composed of [CuCl₄]²⁻ units and water molecules. Both salts exhibit the temperature dependence of the metallic conductivity down to 4.2 K. Spin-spin antiferromagnetic correlations in the Cu²⁺ subsystem were observed in the crystals of 2.     

Dipheno-silyliminoquinones - A 14π-system

Lithium salts of 2.6-dialkylanilines react with di-tert-butylfluorosilanes to give mono (1-3) - and bis (7, 8)-(2.6-dialkylphenylamino)silanes. Amino-2.6-dimethylphenyl-(di-tert-butylfluoro)silane (1) forms with BuLi a dimeric lithium salt (4) containing an eight-membered (LiFNSi)₂ ring system. Thermally, 4 loses LiF and a bicyclic compound (9) via iminosilenes is obtained. The lithium salt of the bulkier amino-2.6-diisopropylphenyl-(di-tert-butylfluorosilanes) (5-7) thermally loses LiH and iminosilanes (10-12) with a 14π-system are isolated. The reaction mechanisms and crystal structures are discussed.