Trimethylsilyl Isocyanate Research Articles

The manipulation of ring-open polymerization process to boost the electrochemical performance for solid-state lithium metal batteries.

Solid-state polyether electrolytes formed by in-situ ring-opening polymerization (ROP) of 1,3-dioxolane (DOL) have attracted great attention due to their high lithium-ion conductivity, and good interface compatibility. However, DOL ring-opening polymerization is difficult to control, resulting in the formation of poly(1,3-dioxolane) (PDOL) with high molecular weight and high crystallinity, which hinder Li+ diffusion and deteriorate the interfacial contact. Herein, trimethylsilyl isocyanate (IPTS) was introduced into DOL ring-opening system as a moisture eliminating agent to weaken the Li salt-based initiating system and regulate the polymerization process. Based on this, the resultant PDOL electrolytes with 3 vol% IPTS exhibit ionic conductivity of 2.8×10-4 S cm-1, a high Li+ transference number (0.68) and excellent stability with Li anode. The Li|PDOL-3%IPTS|Li battery exhibits a stable cycling performance for more than 1100 h under 0.5 mA cm-2 and 0.5 mAh cm-2. Furthermore, the LiFePO4|PDOL-3%IPTS|Li cell shows a capacity retention rate of 89.2% after 200 cycles (25 °C, 1 C) and 94.5% (60 °C, 1 C) after 500 cycles, which is much higher than that of PDOL (6.6%) after 70 cycles (25 °C, 1 C). This work provides guidance for the manipulation of ROP process further to enhance the performance of solid-state lithium metal batteries.

Electrolyte additive strategy to eliminate hydrofluoric acid and construct robust cathode electrolyte interphase for 4.6 V Li||LiCoO2 batteries

The high voltage of Li||LiCoO2 battery can increase the energy density. However, the cycling performance associated with cathode structural stability remains challenging. To address this question, we proposed an electrolyte strategy for improving the performance of 4.6 V Li||LiCoO2 battery by using trimethylsilyl isocyanate (TMIS) as electrolyte additive. The trimethylsilyl group of trimethylsilyl isocyanate can trap HF while the isocyanate group brings polyamide components to the CEI and the SEI. By the synergistic action, the Co3+ dissolution problem of the LiCoO2 cathode was effectively curbed. Furthermore, TMIS regulates the construction of anion-dominated LiF-rich SEI by influencing the solvation structure of Li+. As expected, the 4.6 V Li||LiCoO2 battery with trimethylsilyl isocyanate retains 77.9% initial capacity after 200 cycles at 0.5 C.

Activation and functionalisation of carbon dioxide by bis-tris(pyrazolyl)borate-supported divalent samarium and trivalent lanthanide silylamide complexes.

Synthesis and reactivity with carbon dioxide (CO2) of divalent samarium in the bis-tris(pyrazolyl)borate ligand environment has been reported. In addition, CO2 activation and functionalisation by lanthanide silylamides in the bis-tris(pyrazolyl)borate ligand environment was demonstrated. Reduction of the Sm(III) precursor [Sm(Tp)2(OTf)] (Tp = hydrotris(1-pyrazolyl)borate; OTf = triflate) with KC8 yielded the insoluble Sm(II) multi-metallic coordination polymer [{Sm(Tp)2}n] 1-Sm. Addition of 1,2-dimethoxyethane (DME) to 1-Sm enabled isolation of the monomeric complex [Sm(Tp)2(DME)] 1-Sm(DME). Complex 1-Sm(DME) reduced CO2 to yield the oxalate-bridged dimeric Sm(III) complex [{Sm(Tp)2}2(μ-η2:η2-O2CCO2)] 2-Sm. The reactions of heteroleptic Ln(III) silylamide complexes [Ln(Tp)2(N'')] (Ln = Y, Sm; N'' = N(SiMe3)2) with CO2 yielded monomeric Ln(III) silyloxides [Ln(Tp)2(OSiMe3)] 3-Ln and trimethylsilyl isocyanate (OCNSiMe3). Complexes 3-Ln are the first crystallographically characterised examples of Ln(III)-OSiMe3 bonds accessed via CO2 activation and functionalisation. Full characterisation data are presented for all complexes, including solid-state molecular structure determination by single-crystal X-ray diffraction.

Electrophilically Trapping Water for Preventing Polymerization of Cyclic Ether Towards Low-Temperature Li Metal Battery.

Cyclic ether, such as 1,3-dioxolane (DOL), are promising solvent for low-temperature electrolytes because of the low freezing point. Their use in electrolytes, however, is severely limited since it easily polymerizes in the presence of lithium inorganic salts. The trace water plays a key role via providing the source (proton) for chain initiation, which has, unfortunately, been neglected in most cases. In this work, we present an electrophile, trimethylsilyl isocyanate (Si-NCO), as the water scavenger, which eliminates moisture by a nucleophilic addition reaction. Si-NCO allows DOL to maintain liquid over a wide temperature range even in high-concentration electrolyte. Electrolyte with Si-NCO additive shows promising low-temperature performance. Our finding expands the use of cyclic ether solvents in the presence of inorganic salts and highlights a large space for unexplored design of water scavenger with electrophilic feature for low-temperature electrolytes.

Electrophilically Trapping Water for Preventing Polymerization of Cyclic Ether Towards Low‐Temperature Li Metal Battery

AbstractCyclic ether, such as 1,3‐dioxolane (DOL), are promising solvent for low‐temperature electrolytes because of the low freezing point. Their use in electrolytes, however, is severely limited since it easily polymerizes in the presence of lithium inorganic salts. The trace water plays a key role via providing the source (proton) for chain initiation, which has, unfortunately, been neglected in most cases. In this work, we present an electrophile, trimethylsilyl isocyanate (Si−NCO), as the water scavenger, which eliminates moisture by a nucleophilic addition reaction. Si−NCO allows DOL to maintain liquid over a wide temperature range even in high‐concentration electrolyte. Electrolyte with Si−NCO additive shows promising low‐temperature performance. Our finding expands the use of cyclic ether solvents in the presence of inorganic salts and highlights a large space for unexplored design of water scavenger with electrophilic feature for low‐temperature electrolytes.

Behavior of morpholine and its trimethylsilyl derivative in reactions with trimethylsilyl isocyanate

Objectives. To study the patterns of behavior of morpholine and its trimethylsilyl derivative in reactions with trimethylsilyl isocyanate.Methods. The study employed infrared and nuclear magnetic resonance spectroscopy, as well as elemental analysis.Results. The formation of mixtures of tautomeric forms of silicon-containing urea—N-(trimethylsilyl) morpholine-4-carboxamide and trimethylsilylmorpholine-4-carboximidoate—was established.Conclusions. It is shown that the composition and structure of the resulting products are determined both by the presence of a morpholine substituent at the nitrogen atom and by the type of isocyanate used. Unlike the trimethylsilyl derivative of morpholine, morpholine itself reacts with trimethylsilyl isocyanate to form a mixture of tautomeric forms.

Dinitrogen Cleavage and Functionalization with Carbon Dioxide in a Dititanium Dihydride Framework.

The activation and functionalization of dinitrogen (N2) with carbon dioxide (CO2) are of great interest and importance but highly challenging. We report here for the first time the reaction of N2 with CO2 in a dititanium dihydride framework, which leads to N-C bond formation and N-N and C-O bond cleavage. Exposure of a dinitrogen dititanium hydride complex {[(acriPNP)Ti]2(μ2-η1:η2-N2)(μ2-H)2} (1) (acriPNP = 4,5-bis(diisopropylphosphino)-2,7,9,9-tetramethyl-9H-acridin-10-ide) to a CO2 atmosphere at room temperature rapidly yielded a nitrido/N,N-dicarboxylamido complex {[(acriPNP)Ti]2(μ2-N)[μ2-N(CO2)2]} (2, 28%) and a diisocyanato/dioxo complex {[(acriPNP)Ti]2(NCO)2(μ2-O)2} (3, 52%) with release of H2. When the reaction of 1 with CO2 (1 atm) was carried out at -50 °C, complex 2 was selectively formed in 82% yield within 5 min. Heating 2 at 80 °C under 1 atm CO2 for 30 min afforded 3 in 67% yield. When 1 was allowed to react with 1.5 equiv of CO2 at room temperature, an isocyanato/nitrido/oxo complex {[(acriPNP)Ti]2(NCO)(μ2-N)(μ2-O)} (4) was exclusively formed in 89% yield within 5 min. The reaction of 4 with CO2 at room temperature almost quantitatively yielded the dioxo/diisocyanato complex 3 within 5 min. The mechanistic details were clarified by the 15N- and 13C-labeled experiments and density functional theory (DFT) calculations, providing unprecedented insights into the reaction of N2 with CO2. A titanium-mediated cycle for the synthesis of trimethylsilyl isocyanate Me3SiNCO from N2, CO2, and Me3SiCl using H2 as a reducing agent was also established.

PECULIARITIES OF ISOCYANATES INTERACTION WITH HYDRAZINE DERIVATIVES

The results of studies on chemical transformations of organic and organosilicon isocyanates in their interaction with hydrazine derivatives have been summarized in this review. It is shown that hydrazine and its derivatives including organosilicon compounds reacting with organic isocyanates form corresponding semicarbazides readily enough. The reaction conditions that effect the composition, structure and yield of the resulting target products are presented. A significant difference in the interaction of trimethylsilyl isocyanate with organic and organosilicon derivatives of hydrazine is demonstrated. It is demonstrated that the reason for the impossibility to isolate trimethylsilyl derivatives of semicarbazide is their low hydrolytic stability, as well as high silylating ability. Peculiarities of the reaction of trimethylsilyl isocyanate and dimethylchloromethyl isocyanate silane with 1,1-dimethylhydrazine, its trimethylsilyl analog and isoniazid are given. Possible schemes for the formation of a previously unknown O-trimethylsilyl-1,1-dimethylhydrazinecarboximidoate are presented. The results of using carbofunctional organosilicon isocyanates in these processes are discussed. Basic trends in practical use of the prepared compounds as physiologically active preparations in polymer chemistry and agriculture are shown.

Selective Conversion of CO2 into Isocyanate by Low‐Coordinate Iron Complexes

AbstractDiscovery of the mechanisms for selective transformations of CO2 into organic compounds is a challenge. Herein, we describe the reaction of low‐coordinate Fe silylamide complexes with CO2 to give trimethylsilyl isocyanate and the corresponding Fe siloxide complex. Kinetic studies show that this is a two‐stage reaction, and the presence of a single equivalent of THF influences the rates of both steps. Isolation of a thermally unstable intermediate provides mechanistic insight that explains both the effect of THF in this reaction, and the way in which the reaction achieves high selectivity for isocyanate formation.

Selective Conversion of CO2 into Isocyanate by Low-Coordinate Iron Complexes.

Discovery of the mechanisms for selective transformations of CO2 into organic compounds is a challenge. Herein, we describe the reaction of low-coordinate Fe silylamide complexes with CO2 to give trimethylsilyl isocyanate and the corresponding Fe siloxide complex. Kinetic studies show that this is a two-stage reaction, and the presence of a single equivalent of THF influences the rates of both steps. Isolation of a thermally unstable intermediate provides mechanistic insight that explains both the effect of THF in this reaction, and the way in which the reaction achieves high selectivity for isocyanate formation.

Supersize Cp! Tetrabenzo[a,c,g,i]fluorenyl complexes of yttrium

The synthesis of tetrabenzo[a,c,g,i]fluorenyl (Tbf) yttrium dialkyl complexes, (Tbf)Y(CH2SiMe3)2(L) (L = tetrahydrofuran (THF), 1; L = bipy, 2), by direct protonolysis of the tris(alkyl) complex, Y(CH2SiMe3)3(THF)2, are reported. The X-ray crystal structures of 1 and 2 display the helical twisting typically observed for the Tbf ligand. Dynamic nuclear magnetic resonance (NMR) studies on 1 show a barrier to Tbf helical inversion (epimerization or “wagging”) of 38.1 ± 0.5 kJ mol−1. The reaction of 1 with acidic hydrocarbons such as 1,3-bis(trimethylsilyl)cyclopentadiene or trimethylsilylacetylene results in protonolysis to form the mixed Cp derivative [(Tbf){C5H3(SiMe3)2}Y(CH2SiMe3)(THF)] (3) or [(Tbf)Y(CCSiMe3)2(THF)]n (4), respectively. In the case of 4, a small amount of the trinuclear cluster (Tbf)Y3(μ3-CCSiMe3)2(μ2-CCSiMe3)3(CCSiMe3)3(THF)2 (5) was isolated and characterized by X-ray crystallography. Dialkyl 1 undergoes smooth insertion of trimethylsilyl isocyanate to afford [(Tbf)Y{κ2-(N,O)-Me3SiN(Me3SiCH2)CO}2(THF)] (6) but it does not react with alkenes. Treating 1 with [Ph3C]+[B(C6F5)4]− in bromobenzene generates a moderately active ethylene polymerization catalyst (36 kg mol−1 h−1 bar−1).

A new three-step procedure for the synthesis of cyanuric acid from urea

A new procedure for preparing high-purity cyanuric acid from urea was suggested and experimentally checked. The procedure is based on urea silylation, followed by pyrolysis of the silyl derivative and fractional distillation of the trimethylsilyl isocyanate formed, for which the temperature limits of mild hydrolysis were determined.

ChemInform Abstract: An Efficient Synthesis of 15N-Hydroxyurea.

Abstract Treatment of trimethylsilyl isocyanate with 15N-hydroxylamine hydrochloride produces 15N-hydroxyurea, a valuable pharmacological tool, in an efficient, one-pot procedure in 74% yield. Recrystallization of the crude product yields analytically pure material in 47% overall yield.

ZrO<SUB align=right>2 nanocomposites from polyzirconosiloxanes

Polyzirconosiloxanes were synthesised trough the hydrolytic co-condensation of tetraethoxysilane (TEOS), methyltriethoxysilane (MTES) and zirconium isopropoxide (ZIP) (Process A) or tetramethoxysilane (TMOS), trimethylsilyl isocyanate (TMSI) and ZIP (Process B). In both processes, ethylacetoacetat was added to provide ethylacetato derivatives of polyzirconosyloxanes. When the obtained hybrids were subjected to heat treatment, the zirconia component crystallises in nano size. The XRD, FTIR and 29Si NMR showed that the crystallisation depends on the random and block sequence in the main chain of the polyzirconosiloxanes derived from Processes A and B, respectively.

Design, Synthesis, and Evaluation in Vitro of Quinoline-8-carboxamides, a New Class of Poly(adenosine-diphosphate-ribose)polymerase-1 (PARP-1) Inhibitor

Poly(ADP-ribose)polymerase-1 is an important target enzyme in drug design; inhibitors have a wide variety of therapeutic activities. A series of quinoline-8-carboxamides was designed to maintain the required pharmacophore conformation through an intramolecular hydrogen bond. 3-Substituted quinoline-8-carboxamides were synthesized by Pd-catalyzed couplings (Suzuki, Sonogashira, Stille) to 3-iodoquinoline-8-carboxamide, an efficient process that introduces diversity in the final step. 2-Substituted quinoline-8-carboxamides were prepared by selective Pd-catalyzed couplings at the 2-position of 2,8-dibromoquinoline, followed by lithium-bromine exchange of the intermediate 2-(alkyl/aryl)-8-bromoquinolines and reaction with trimethylsilyl isocyanate. The intramolecular hydrogen bond was confirmed by X-ray and by NMR. The SAR of the 3-substituted compounds for inhibition of human recombinant PARP-1 activity showed a requirement for a small narrow group. Substituents in the 2-position increased potency, with the most active 2-methylquinoline-8-carboxamide having IC(50) = 500 nM (IC(50) = 1.8 microM for 5-aminoisoquinolin-1-one (5-AIQ, a standard water-soluble inhibitor)).

Preparation of nanostructured porous SiO2-Al2O3 oxycarbonitride materials obtained by a new chemical precursor method

AbstractNanostructured hybrid materials containing Al2O3 were synthesized via a sol-gel method through hydrolysis and co-condensation reactions using trimethylsilyl isocyanate (TMSI) as a new silica source in the presence of tetramethoxysilane (TMOS) and three different quantities (10, 20 and 30 wt.%) of aluminum sec-butoxide (Al(OBusec)3 as a modifying agent. The xerogel nanostructured materials are pyrolyzed in nitrogen atmosphere in the temperature range from 400°C to 1100°C. The transformation of the xerogel hybrid networks into Al-Si oxycarbonitride materials has been investigated by XRD, FTIR, SEM, AFM, and 29Si MAS-NMR. To the best of our knowledge, the work reported here is the first synthesis of porous di-urethanesils modified with aluminum and one of the few examples of alumosilica oxycarbonitride materials

Design of new heteroscorpionate ligands and their coordinative ability toward Group 4 transition metals; an efficient synthetic route to obtain enantiopure ligands

The reaction of different types of bis(pyrazol-1-yl)methane derivatives with Bu(n)Li and alkyl or aryl-containing-isocyanates or isothiocyanates, some of these as chiral reagents, gives rise to the preparation of new heteroscorpionate ligands in the form of the lithium derivatives [Li(NNE)]2 (1-10), although a similar process with trimethylsilyl isocyanate or isothiocyanate gave the complexes [Li(NCX)(bdmpzs)(THF)](X = O, 11; X = S, 12)[bdmpzs = bis(3,5-dimethylpyrazol-1-yl)trimethylsilylmethane]. Compounds 1-8 reacted with [TiCl4(THF)2] or [MCl4](M = Zr, Hf) to give a series of cationic complexes [MCl3{kappa3-NNE(H)}]Cl (13-36) where the heteroscorpionate ligand contains either an acetamide or thioacetamide group resulting from the protonation of the corresponding acetamidate or thioacetamidate. However, under appropriate experimental conditions neutral Ti complexes were isolated-namely [TiClx(NMe2)3-x(S-mbbpam)](37-39)[S-mbbpam =(S)-(-)-N-alpha-methylbenzyl-2,2-bis(3,5-dimethylpyrazol-1-yl)acetamidate]. Finally, two alkoxide-containing titanium complexes [TiClx(OR)3-x(S-mbbpamH)]Cl (40-41) were also prepared. The structures of these complexes have been determined by spectroscopic methods and, in addition, the X-ray crystal structures of 1, 12, and 19 were also established.

Mechanism of the alternating copolymerization of epoxides and CO2 using beta-diiminate zinc catalysts: evidence for a bimetallic epoxide enchainment.

A series of zinc beta-diiminate (BDI) complexes and their solid-state structures, solution dynamics, and copolymerization behavior with CO(2) and cyclohexene oxide (CHO) are reported. Stoichiometric reactions of the copolymerization initiation steps show that zinc alkoxide and bis(trimethylsilyl)amido complexes insert CO(2), whereas zinc acetates react with CHO. [(BDI-2)ZnOMe](2) [(BDI-2) = 2-((2,6-diethylphenyl)amido)-4-((2,6-diethylphenyl)imino)-2-pentene] and (BDI-1)ZnO(i)Pr [(BDI-1) = 2-((2,6-diisopropylphenyl)amido)-4-((2,6-diisopropylphenyl)imino)-2-pentene] react with CO(2) to form [(BDI-2)Zn(mu-OMe)(mu,eta(2)-O(2)COMe)Zn(BDI-2)] and [(BDI-1)Zn(mu,eta(2)-O(2)CO(i)Pr)](2), respectively. (BDI-2)ZnN(SiMe(3))(2) inserts CO(2) and eliminates trimethylsilyl isocyanate to give [(BDI-2)Zn(mu-OSiMe(3))](2). [(BDI-7)Zn(mu-OAc)](2) [(BDI-7) = 3-cyano-2-((2,6-diethylphenyl)amido)-4-((2,6-diethylphenyl)imino)-2-pentene] reacts with 1.0 equiv of CHO to yield [(BDI-7)Zn(mu,eta(2)-OAc)(mu,eta(1)-OCyOAc)Zn(BDI-7)]. Under typical polymerization conditions, rate studies on the copolymerization exhibit no dependence in [CO(2)], a first-order dependence in [CHO], and orders in [Zn](tot) ranging from 1.0 to 1.8 for [(BDI)ZnOAc] complexes. The copolymerizations of CHO (1.98 M in toluene) and 300 psi CO(2) at 50 degrees C using [(BDI-1)ZnOAc] and [(BDI-2)ZnOAc] show orders in [Zn](tot) of 1.73 +/- 0.06 and 1.02 +/- 0.03, respectively. We propose that two zinc complexes are involved in the transition state of the epoxide ring-opening event.

ChemInform Abstract: Interaction of Trimethylsilyl Isocyanate with Xenon Difluoride and Fluoroxenonium Triflate in the Presence of Alkenes.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform Abstract: Xenon Difluoride—Trimethylsilyl Isocyanate—Triflic Acid as a New System for the Amination of Aromatic Compounds.

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.