Trimethylsilyl Phosphite Research Articles

Solvent-Free Synthesis of α-Cyanophosphonates from β-Nitro­styrenes by Using a Deep-Eutectic Solvent Catalyst

Abstractα-Cyanophosphonates, which are useful reagents for the Horner–Wittig reaction, were synthesized under solvent-free conditions by using a choline chloride–zinc chloride deep-eutectic solvent (DES) as a catalyst. This is only the second report on the synthesis of these compounds. In the previous report, diethyl trimethylsilyl phosphite was used as a reagent and TiCl4 as a catalyst, whereas in this study, both the reagent (triphenylphosphine) and the catalyst (choline chloride–zinc chloride DES) are cheaper, more readily available, and less harmful than those used in the previous work. Moreover, the process involves an interesting cascade reaction between a β-nitrostyrene and two equivalents of triphenyl phosphite, leading to the desired product by a new synthetic route. The products can be used in the pharmaceutical and agricultural industries, in addition to their synthetic applications in the preparation of α,β-unsaturated nitriles. The reactions were completed on using 20 mol% of DES at 80 °C in six hours. Ten different β-nitrostyrenes were synthesized in yields of 55–87% after purification. β-Nitrostyrenes containing electron-donating groups showed higher yields. The reaction failed when aliphatic or heteroaromatic nitroalkenes or β-nitrostyrenes with electron-withdrawing substituents were employed. Finally, three plausible mechanistic routes are proposed for the reaction, starting with the nucleophilic addition of triphenyl phosphite to the carbon, nitrogen, or oxygen atom in the α-position.

Ag-coated 3D groove as a study platform in evaluating the throwing power of electrolytes for Li metal batteries

Selecting electrolytes is critical before assembling a cell to achieve good performance in a Li metal battery. An Ag-coated groove with hill and valley features is prepared by magnetron sputtering on a 3D structure array pattern laying on a commercial Cu foil to act as a platform to evaluate liquid electrolytes in Li//Cu half-cell configuration. The 3D Ag-coated groove with hill and valley feature provides the capability to determine the uniformity in terms of throwing power (TP) of various electrolytes, which is correlated with their electrochemical performance. The increase in TP value after applying fluoroethylene carbonate (FEC) (−3.59%) and tris(trimethylsilyl) phosphite (TMSP) (−49.60%) as an additive is in contrast to the TP value of the pristine electrolyte w/o additive (−66.84%), which is in line with the higher average coulombic efficiency achieved (95.39% for FEC and 94.87% for TMSP) compared to LiPF6 alone (91.89%). Moreover, the FEC-contained electrolyte achieves the lowest value of resistance (18.76 Ω and 10.92 Ω) and average surface roughness Ra (24.8 and 22.4 nm) on hill and valley, respectively, among the investigated electrolytes. Applying the design of an Ag-coated groove gives significant insight into how a platform can be built to comply with the effort in screening the good options for liquid electrolytes in Li metal battery application.

Development of Electrolyte Additives to Enable High-Voltage LiNi0.5Mn1.5O4 Lithium Ion Batteries

Electrochemical energy storage (EES) is still key to realize wide spread use of renewable energies. For large-scale EES production, the development of high energy density, non-toxic, cost-effective materials is necessary. In this study, a cobalt free active material, Lithium Nickel Manganese Oxide, LiNi0.5Mn1.5O4 (LNMO), was employed in the production of cathodes for high voltage lithium ion battery (LIB) applications. LNMO is an attractive cathode active material due to its high operating potential (~4.7 vs. Li/Li+ [1]), non-toxicity and low cost. The practical application of LNMO cathodes in LIBs has been relatively limited, especially for large scale application, due challenges associated with the material (i.e. electrolyte decomposition at high voltage, self-discharge and dissolution of the transition metals [2]).Electrolyte additives are an effective way to address these challenges, without major cost increase or changes to the production approach. In this study the role of different electrolyte additives in high-voltage full-cell LIBs with both graphite and silicon-graphite anodes is investigated. Additives known for their solid electrolyte interphase (SEI) forming ability (i.e. vinylene carbonate (VC) and fluoroethylene carbonate (FEC)), as well as additives that play additional roles such as cathode electrolyte interface formation or HF scavenging (i.e. tris(trimethylsilyl) phosphite (TMSP) and succinate anhydride (SA)), are used [3]. Galvanostatic cycling measurements were performed in 3-electrode cells in order to investigate the rate capability and long term cycling stability of LMNO/Gr and LMNO/Gr-Si full-cells with different electrolyte additives. The electrochemical characterization was verified with post mortem analysis to confirm the SEI composition, chemical and mechanical stability of the electrodes and lack of lithium plating. Post mortem investigations were done with Raman spectroscopy, scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX) and optical microscopy. Improved rate performance and better long term cycling stability of both full-cell chemistries was achieved for electrolytes containing the TMSP additive.

Multifunctionalizing electrolytes in situ for lithium metal batteries

Lithium metal batteries (LMBs) are next-generation high-energy rechargeable batteries, in which an ideal multifunctional electrolyte additive has been desired to simultaneously stabilize the electrolyte salt, scavenge the electrolyte detrimental impurities, and protect both the lithium anode and cathode. Here, we report a new concept of introducing Lewis acid-base coordinations into electrolytes to synthesize Lewis acid-base complexes in situ as multifunctional electrolyte additives for LMBs. For proof of concept, by introducing fluoroethylene carbonate (FEC) as the Lewis acid and tris(trimethylsilyl) phosphite (TMSP) as the Lewis base into a conventional carbonate electrolyte, an acid-base complex (TMSP: FEC) is formed in situ to act as an electrochemically-clean environment for cleaning and stabilizing the electrolyte while reinforcing the electrode surface coatings with multi-components from the complex. The preferential reduction and oxidation of the complex derive mechanically strong and lithium-ion conductive surface coatings to protect the lithium anode and cathode, respectively. Synergistically, these multifunctionalities of the complex ensure an extraordinary Li platting/stripping with an extremely low polarization overpotential of 11 mV for over 16,000 h, and thereby enable high-performance LMBs based on a high-potential LiNi0.5Mn1.5O4, high-capacity LiNi0.8Mn0.1Co0.1O2, or high-safety LiFePO4 cathode with a high packing and high areal capacity. This work opens up a new avenue for in-situ multifunctionalizing electrolytes for LMBs and beyond.

Tris(trimethylsilyl) Phosphite and Lithium Difluoro(oxalato)borate as Electrolyte Additives for LiNi0.5Mn1.5O4‐Graphite Lithium‐Ion Batteries

AbstractRaising the energy density of lithium‐ion batteries (LIBs) through the operation of high‐voltage cathodes presents a challenge in terms of practical use due to electrolyte degradation. Consequently, it is imperative to explore new materials to circumvent this issue. In this study, a combination of tris(trimethylsilyl) phosphite (TMSPi) and lithium difluoro(oxalato)borate (LiDFOB) is presented as film‐forming additives in a conventional LiPF6‐containing carbonate‐based electrolyte solution in high‐voltage LiNi0.5Mn1.5O4‐graphite full cells. At high voltage, TMSPi oxidizes on the LiNi0.5Mn1.5O4 (LNMO) cathode surface prior to the decomposition of electrolyte solvents, promoting the formation of a stable cathode electrolyte interphase (CEI) layer. In tandem, given that LiDFOB has a lower reduction potential than ethylene carbonate (EC), it has the possibility of forming a solid electrolyte interphase (SEI) on the graphite anode surface. Combining the two additives was found to suppress the degradation of the electrolyte to a large extent. Among the investigated concentration of the additives, the combination of 1 wt. % TMSPi and 2 wt. % LiDFOB added to LP40 electrolyte exhibits improved capacity retention of 80 % after 400 cycles at 0.3 C, compared to the electrolyte with no additive with 67 % capacity retention over the same period. Thereby, the combination of TMSPi with LiDFOB provides an improvement for high voltage LIBs.

Tailoring solvation chemistry in carbonate electrolytes for all-climate, high-voltage lithium-rich batteries

High-voltage Li-rich layered oxide materials (LLOs) are considered as the promising next-generation cathode materials because of their high energy density and low cost. However, their electrochemical performance continues to deteriorate under high voltages when using traditional lithium hexafluorophosphate (LiPF6)-based carbonate electrolytes, mostly due to the detrimental reactions with free anions, unstable electrode interface and limited Li+ kinetic process. Here, we demonstrate a highly oxidation-resistant carbonate electrolyte by incorporating multifunctional lithium difluoro(oxalato)borate (LiDFOB) and Tris(trimethylsilyl) Phosphite (TMSPi) additives. It is discovered that the introduction of LiDFOB and TMSPi can manipulate the electrolyte solvation structure by reducing the number of coordinated solvent molecules and free PF6−anions at the electrolyte-electrode interface, thus promoting the desolvation process of Li+, suppressing the generation of harmful HF species and conducive to forming a thin and robust cathode electrolyte interphase (CEI) layer. As a result, the Li||LLO cells with dual additives show excellent cycle stability and improved rate capability in a wide temperature ranged from -20 °C to 55 °C, and the retention rate of LLO||graphite pouch cell (2.5 Ah) using EEDB-TMSPi electrolyte is up to 91.1% after 200 cycles. It is anticipated that the work provides a promising strategy for realizing long-cycle stability of layered cathode materials under high-voltage and wide-temperature conditions.

Highly Durable and Ultrafast Cycling of Dual‐Ion Batteries via In Situ Construction of Cathode–Electrolyte Interphase

AbstractDual‐ion batteries have shown promising prospect in energy storage, owing to their low material costs, high power capability, and environmental friendliness. However, graphite as the cathode always suffers from structural damage and electrode/electrolyte interface instability, which greatly deteriorate their electrochemical performance. Here, tris(trimethyl‐silyl) phosphite (TMSP) is added as an electrolyte additive to improve the electrochemical performance. TMSP not only scavenges the deleterious species generated by electrolytes, but also produces a thin and uniform cathode–electrolyte interphase layer on graphite. Hence, the electrochemical performance is greatly promoted. In graphite||graphite, the capacity retention is ≈96.8% at 30 °C or 92.5% after 3000 cycles in the presence of TMSP, much better than those without TMSP (62% at 30 °C or 27% after 200 cycles).

Evolution of Interfacial Phenomena Induced by Electrolyte Formulation and Hot Cycling of Anode-Free Li-Metal Batteries

Even though the anode-free lithium metal battery (AFLMB) is the next promising energy-storage device because of its high energy density, the irreversible interfacial phenomena at the Cu/electrolyte interface are the key failure mechanisms of the AFLMBs. To the best of our knowledge, the interfacial phenomena associated with the capacity fading of AFLMBs are not reported yet. Herein, hot cycling combined with electrolyte formulation using 1% tris(trimethylsilyl) phosphite (TMSP) additive has been used as a protocol to systematically investigate the Cu/electrolyte interfacial phenomena of Li nucleation, compactness of deposited Li, inactive Li (“dead Li” and Li for solid–electrolyte interphase (SEI) formation “SEI-Li”), electrolyte decomposition, and SEI layer formation using a scanning electron microscope, scanning electron microscope-focused ion beam, titration gas chromatography, in situ gas chromatography–mass spectroscopy, and X-ray photoelectron spectroscopy, respectively. The synergy of hot cycling and the TMSP additive lowers the nucleation barrier in Li/Cu from 76.2 to 21.7 mV and increases the compactness of deposited Li from 32.3 to 43.8% and decreases “dead Li” from 45.18 to 10.86% and SEI-Li from 31.04 to 12.49% of anode-free Cu/NMC111. Because of the synergy effects, the Cu/NMC111 cell provides over 100 cycles with an average coulombic efficiency (avg. CE) of 98.6% for the first 60 cycles and a capacity retention (CR) of 60.4% at the end of the 60th cycle at 0.2/0.5 mA cm–2 charger/discharge current density, while the cell with 1 M LiPF6 EC/DEC at 25 °C offers only an avg. CE of 92.8% for the first 15 cycles with a CR of 40.4% at the 15th cycle. The results suggest that the synergy of hot cycling and electrolyte formulation decreases the surface area of deposited Li and stabilizes the interface that suppresses inventory Li loss. This work probes the Cu/electrolyte interfacial phenomena, attributed to the failure mechanisms of AFLMBs. It also sheds light on suitable strategies to stabilize the Cu interface for stable cycling of AFLMBs.

Synergistic Effect of TMSPi and FEC in Regulating the Electrode/Electrolyte Interfaces in Nickel-Rich Lithium Metal Batteries.

Nickel-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) with respect to Li metal can enhance the energy density of lithium batteries effectively. However, the unstable Li deposition, together with the dissolution and migration of transition metal (TM) ions toward the anode deteriorate the cycle performance of NCM811||Li battery, especially when commercial carbonate electrolyte is used. Herein, tris(trimethylsilyl)phosphite (TMSPi) and fluoroethylene carbonate (FEC) are used to construct a dual-additive electrolyte, by which both electrodes can be protected. It is found that TMSPi can be preferentially adsorbed on the cathode surface through its strong coordination with Ni4+, playing the role as a HF scavenger and suppressing TM ions dissolution, as well as mitigating the structural degradation of the cathode effectively. When it comes to the lithium anode, the presence of TMSPi may lead to side reactions with Li metal, accompanied by fast dendrite growth. The introduction of FEC could facilitate the formation of stable electrode/electrolyte interfaces on both sides. Particularly, reduce the direct contact between TMSPi and Li anode, thus ameliorate the incompatibility issue. Consequently, the NCM811||Li cell with dual-additive demonstrates excellent capacity retention of 81.2% after 500 cycles at 1 C rate. As a sharp contrast, it only retains 13.9% in the one with blank electrolyte. The findings of this work provide a new insight into enhancing the cycle performance of NCM811||Li system via the synergistic effect between additives.

Tris(trimethylsilyl) phosphite (TMSPi) as an electrolyte additive for LiNi0.5Co0.2Mn0.3O2 cathode materials at elevated voltage and temperature

Electrolyte additive tris(trimethylsilyl) phosphite (TMSPi) was used to promote the electrochemical performances of LiNi[Formula: see text]Co[Formula: see text]Mn[Formula: see text]O2 (NCM523) at elevated voltage (4.5 V) and temperature (55[Formula: see text]C). The NCM523 in 2.0 wt.% TMSPi-added electrolyte exhibited a much higher capacity (166.8 mAh/g) than that in the baseline electrolyte (118.3 mAh/g) after 100 cycles under 4.5 V at 30[Formula: see text]C. Simultaneously, the NCM523 with 2.0 wt.% TMSPi showed superior rate capability compared to that without TMSPi. Besides, after 100 cycles at 55[Formula: see text]C under 4.5 V, the discharge capacity retention reached 87.4% for the cell with 2.0 wt.% TMSPi, however, only 24.4% of initial discharge capacity was left for the cell with the baseline electrolyte. A series of analyses (TEM, XPS and EIS) confirmed that TMSPi-derived solid electrolyte interphase (SEI) stabilized the electrode/electrolyte interface and hindered the increase of interface impedance, resulting in obviously enhanced electrochemical performances of NCM523 cathode materials under elevated voltage and/or temperature.

Dimethyl trimethylsilyl phosphite as a novel electrolyte additive for high voltage layered lithium cobaltate-based lithium ion batteries

The addition of 0.5 wt.% of DMTMSP to the electrolyte could improve the low-temperature discharge and cycling performances of high voltage layered lithium cobaltate-based lithium ion batteries.

Phosphorus-containing star-shaped polymer conjugates for biomedical applications

A novel phosphorus-containing biocompatible and biodegradable star-shaped polymer was designed as a precursor polymer for obtaining sugar or drug conjugates. The star polymer bearing three arms was synthesized applying the “coupling on” approach. Linear oligo(oxyethylene H-phosphonate) with a terminal hydroxyl group was prepared and used as functional arms able to react with tris(2,3-epoxypropyl) isocyanurate as core in the presence of boron trifluoride etherate as catalyst. The H-phosphonate moieties in the arm chains were transformed into trimethylsilyl phosphite groups and further via Staudinger reaction they were converted into phosphoramidates bearing specific residues. When the Staudinger reaction was carried out with a glucose-containing azide, i.e. 2-p-azidobenzamide-2-deoxy-1,3,4,6-tetra-O-trimethylsilyl-alpha-D-glucopyranose, the product was a star-shaped glycopolymer. The conjugation of AZT yielded a star-shaped polymer-drug conjugate. Multinuclear NMR spectroscopy was applied as a powerful tool for determination of the conversion and structure of the reaction products. Analytical ultracentrifugation, dynamic and electrophoretic light scattering techniques were used for characterization of the star polymers and conjugates, as well as in binding studies with Concanavalin A. Drug release measurements and cytotoxicity tests were also performed. The obtained results evidenced feasible synthetic procedures for preparation of biocompatible phosphorus containing star-shaped glycopolymer and drug conjugate.

Understanding the Roles of Tris(trimethylsilyl) Phosphite (TMSPi) in LiNi0.8Mn0.1Co0.1O2 (NMC811)/Silicon–Graphite (Si–Gr) Lithium‐Ion Batteries

AbstractThe coupling of nickel‐rich LiNi0.8Mn0.1Co0.1O2 (NMC811) cathodes with high‐capacity silicon–graphite (Si–Gr) anodes is one promising route to further increase the energy density of lithium‐ion batteries. Practically, however, the cycle life of such cells is seriously hindered due to continuous electrolyte degradation on the surfaces of both electrodes. In this study, tris(trimethylsilyl) phosphite (TMSPi) is introduced as an electrolyte additive to improve the electrochemical performance of the NMC811/Si–Gr full cells through formation of protective surface layers at the electrode/electrolyte interfaces. This is thought to prevent the surface fluorination of the active materials and enhance interfacial stability. Notably, TMSPi is shown to significantly reduce the overpotential and operando X‐ray diffraction (XRD) confirms that an irreversible “two‐phase” transition reaction caused by the formed adventitious Li2CO3 layer on the surface of NMC811 can transfer to a solid‐solution reaction mechanism with TMSPi‐added electrolyte. Moreover, influences of TMSPi on the cathode electrolyte interphase (CEI) on the NMC811 and solid electrolyte interphase (SEI) on the Si–Gr are systematically investigated by electron microscopy and synchrotron‐based X‐ray photoelectron spectroscopy which allows for the nondestructive depth‐profiling analysis of chemical compositions and oxidation states close to the electrode surfaces.

Electrolyte Additives in Lithium Ion EV Batteries and the Relationship of the SEI Composition to Cell Resistance and Lifetime

Sulphur, boron and phosphorous containing electrolyte additives were evaluated in cells containing pristine electrodes from a commercial EV lithium ion cell against a standard baseline electrolyte. Following formation and a full cell ageing step, cycling performance and impedance spectroscopy were used to elucidate the most effective additives. The additive tris trimethyl silyl phosphite (TTSPi) showed the most promise; with improved cell capacities and reduced impedances observed after formation. X-ray photoelectron spectroscopy (XPS) measurements on anode elemental surface profiles were correlated with the electrochemical performance. It was observed that increased lithium fluoride content on the surface of the anodes typically produced cells with lower impedance. Sulphur containing additives also showed improved cell behaviours; and the decomposition and chemical reactions of these compounds at the anode surface is discussed in detail. The main influence of TTSPi was to reduce the amount of oxygen (C=O) and sulphur in the electrolyte interphase (SEI) layer; to be replaced with hydrocarbons.

Synthesis of new functionalized aryl and pyridyl aminomethylenebisphosphonic acids and their derivatives via silicon-assisted methodology

The new convenient synthesis of functionalized aryl and pyridyl aminomethylenebisphosphonic acids and their derivatives has been developed via silicon-assisted methodology. New functionalized aminomethylenebisphosphonic acids containing pyridines moieties were obtained using unique reaction of tris(trimethylsilyl) phosphite with N-formyl aminopyridines and trimethylsilyl triflate as a catalyst under mild conditions. Intermediates – tetra(trimethylsilyl) aminomethylenebisphosphonates formed, were converted to the target acids by further treatment with methanol excess. In contrast the corresponding tetraethyl aminomethylenebisphosphonates were synthesized under heating (130 °C) of four component mixture (diethyl trimethylsilyl phosphite, triethyl orthoformate, aryl- or pyridylamine, and diethyl phosphite) in the presence of zinc chloride catalyst. The catalytic schemes of target substances formation are proposed and thoroughly discussed.

Improving cyclic stability of LiNi0.6Co0.2Mn0.2O2-SiOx/graphite full cell using tris(trimethylsilyl)phosphite and fluoroethylene carbonate as combinative electrolyte additive

Fluoroethylene carbonate (FEC) has been proven an effective electrolyte additive for silicon-based Li-ion cells. However, studies have shown that it will promote the formation of acid during storage and cycling in LiPF6-based electrolyte, thus deteriorating the performance of cell. Herein, tris(trimethylsilyl)phosphite (TMSPi) and fluoroethylene carbonate (FEC) are used as combinative electrolyte additive for LiNi0.6Co0.2Mn0.2O2-SiOx/graphite (NCM622-SiOx/Gr) coin-type full cell. Electrolyte storage experiments show that TMSPi can eliminate the acid present in FEC-containing electrolyte. Theoretical calculations and electrochemical analysis confirm that TMSPi could be oxidized previously on NCM622 to optimize the cathode electrolyte interphase (CEI) and FEC can also be reduced in advance on SiOx/Gr to modify the solid electrolyte interphase (SEI). Such a full cell with 3% TMSPi + 5% FEC as electrolyte additive has the best electrochemical performance; the specific discharge capacity is maintained at 156.1 mAh g−1 after 200 cycles at rate of 1 C between 2.8 and 4.25 V. X-ray photoelectron spectroscopy results of electrode surface show that CEI has a certain amount of Li2CO3 and LixPOyFz and lower LiF, while SEI has a certain amount of Li2CO3 and LiF and less LixPOyFz, which could be beneficial to improve the cyclic stability of NCM622-SiOx/Gr full cell.

Elucidating the Reactivity of Tris(trimethylsilyl)phosphite and Tris(trimethylsilyl)phosphate Additives in Carbonate Electrolytes—A Comparative Online Electrochemical Mass Spectrometry Study

The electrolyte additives tris(trimethylsilyl)phosphite (TMPSi) and tris(trimethylsilyl)phosphate (TMSPa) have shown their potential to improve lifetime and decrease impedance build-up in lithium i...

A novel hydroxy-bisphosphonic acid prodrug as a candidate for the delivery of ibuprofen to bone

Active targeting with controlled delivery of anti-inflammatory drugs to the bone is not sufficiently explored. In this study, concise and novel synthesis of a hydroxy-bisphosphonic acid (HBPA) prodrug containing ibuprofen is described. The key step consisted of preparing the HBPA function from a carboxylic acid precursor, in mild conditions and using appropriate Arbuzov reactions with tris(trimethylsilyl)phosphite. This prodrug would be an excellent candidate for the treatment of bone inflammation diseases such as rheumatoid arthritis.

Deciphering the Interface of a High‐Voltage (5 V‐Class) Li‐Ion Battery Containing Additive‐Assisted Sulfolane‐Based Electrolyte

AbstractNext generation high energy density lithium‐ion batteries have aroused great interests worldwide. Herein, in a high‐voltage (5 V‐class) LiNi0.5Mn1.5O4/MCMB (graphitic mesocarbon microbeads) battery system using 1 m lithium difluoro(oxalate)borate/sulfolane, tris(trimethylsilyl) phosphite (TMSP) additive is added to significantly improve room/high temperature cycling performances. The unchanged X‐ray diffraction patterns suggest the bulk crystal structure of cycled MCMB anode and LiNi0.5Mn1.5O4 cathode are well preserved. Moreover, soft X‐ray absorption spectroscopy (XAS) taken from bulk sensitive fluorescence‐yield (FY) mode reveals the unchanged bulk electronic structure of cycled LiNi0.5Mn1.5O4 cathode. Therefore, it is concluded that only interface instability contributes to capacity fading of full‐cells. However, electrode/electrolyte interface and corresponding interfacial reaction processes are always “enigmatic.” First, X‐ray photoelectron spectroscopy (XPS) and in situ differential electrochemical mass spectrometry (DEMS) are used to more accurately decipher the TMSP additive action mechanism in MCMB/electrolyte interfacial reaction processes, by identifying the interfacial solid and gas byproducts, respectively. Then, the crucial role of TMSP additive in modifying cathode/electrolyte interface is revealed by XPS and soft XAS taken from surface sensitive total electron yield (TEY) mode. This paper provides valuable perspectives for formulating novel electrolytes, and for more accurately depicting additive action mechanism in “enigmatic” electrode/electrolyte interfacial reaction processes.

New Synthesis of Diethyl Trimethylsilyl Phosphite

Diethyl phosphonate rapidly reacted with hexamethyldisilazane at 20°C in the presence of 52 mol % of zinc(II) chloride to give 76% of diethyl trimethylsilyl phosphite.