| HS Code | 511834 |
| Product Name | Bis(Chlorosulfonyl)Imide |
| Chemical Formula | Cl2HNO4S2 |
| Molecular Weight | 214.05 g/mol |
| Cas Number | 15873-42-4 |
| Iupac Name | N-(chlorosulfonyl)sulfamoyl chloride |
| Appearance | White to off-white crystalline solid |
| Physical State At 25 C | Solid |
| Melting Point | 36-38 °C |
| Boiling Point | 90-92 °C at 0.1 mmHg |
| Density | 1.98 g/cm³ at 25 °C |
| Refractive Index | 1.526 (n20/D) |
| Solubility | Reacts with water; soluble in polar organic solvents |
| Storage Conditions | Keep cool, dry, under inert gas |
| Moisture Sensitivity | Moisture sensitive |
| Corrosivity | Corrosive to skin, eyes, and metals |
| Hazard Classification | Danger; causes severe skin burns and eye damage |
As an accredited Bis(Chlorosulfonyl)Imide factory, we enforce strict quality protocols—every batch undergoes rigorous testing to ensure consistent efficacy and safety standards.
| Packing | Bis(Chlorosulfonyl)Imide supplied in 100 g amber glass bottles with PTFE-lined caps under inert gas, labeled corrosive. |
| Container Loading (20′ FCL) | Bis(Chlorosulfonyl)Imide is loaded in a 20′ FCL container using suitable drums, properly secured, kept dry, and protected from moisture. |
| Shipping | Ship as a corrosive, moisture-sensitive inorganic hazardous material under UN3264, Class 8, with packing group per SDS. Use UN-approved leakproof packaging, absorbent, secondary containment, and corrosive labels. Keep dry, cool, ventilated; segregate from water, bases, oxidizers. Follow DOT/IATA/IMDG rules. Trained personnel only. |
| Storage | Store Bis(chlorosulfonyl)imide in a cool, dry, well-ventilated, fire-resistant area away from water, moisture, bases, oxidizers, and organic matter. Keep in sealed, corrosion-resistant containers under inert gas (nitrogen or argon), with secondary containment. Protect from light and impacts. Use acid-resistant cabinets, appropriate ventilation, and clear corrosive/moisture-sensitive labeling. |
| Shelf Life | Moisture-sensitive; store sealed under inert gas at low temperature. Typical shelf life 6–12 months when protected from moisture and heat. |
On a production line configured for LiFSI, bis(chlorosulfonyl)imide is transferred under dry nitrogen at −20 °C from a sealed IBC into a 2,000 L reactor. The vessel is lined with PTFE and fitted with a Hastelloy C-276 agitator; the mechanical seal is purged with dry nitrogen at 50 mL/min to exclude moisture. Anhydrous hydrogen fluoride is charged at 0.8–1.0 mol per chlorine centre while the mass temperature is held at −10 °C during the first 30 min of addition. The reaction mass is then warmed to 25–35 °C and held at 0.2–0.4 MPa gauge for 8 h. A caustic scrubber charged with 10 wt% potassium hydroxide captures HCl and SO₂ off-gas. Conversion is monitored by argentometric titration of chloride in an ice-cold aliquot; complete fluorination releases 2 mol chloride per mole of imide. The accepted endpoint for battery-grade LiFSI is a residual S–Cl content below 0.5 mol%; higher residuals appear as chloride defects after neutralization and cause aluminium current collector failure. The resulting bis(fluorosulfonyl)imide is neutralized at 0–5 °C with lithium hydroxide monohydrate dispersed in 1,2-dimethoxyethane. The aqueous phase is separated and washed twice with ice-cold solvent. The organic extract is concentrated on a wiped-film evaporator at 60–70 °C under 0.5–1.0 kPa, then dried in a conical vacuum dryer at 110 °C until water by ISO 760:1978 is below 80 ppm. Finished LiFSI is qualified by ion chromatography for chloride below 50 ppm and sulfate below 200 ppm. An electrolyte blend containing 1.0 M LiFSI in ethylene carbonate/ethyl methyl carbonate (3:7 vol:vol) is evaluated in coin cells against a LiNi₀.₈Mn₀.₁Co₀.₁O₂ cathode and graphite anode over 2.8–4.2 V per IEC 62660-1:2018. Aluminium current collectors are tested separately by linear sweep voltammetry to 5.0 V versus Li/Li⁺ at 60 °C; a pitting current below 10 µA·cm⁻² at 4.2 V is accepted. Batch-to-batch S–Cl residual variance on production lines is typically 0.1–0.4 mol% depending on moisture ingress in the HF feed, which is the principal source of failure in this downstream track.
Bis(chlorosulfonyl)imide is first converted to bis(fluorosulfonyl)imide and then cation-exchanged with a quaternary ammonium or pyrrolidinium hydroxide to yield room-temperature ionic liquids such as 1-ethyl-3-methylimidazolium FSI or N-butyl-N-methylpyrrolidinium FSI. The neutralization is run in aqueous or alcoholic media at 0–10 °C because the imide anion undergoes slow hydrolysis at pH above 9 and temperature above 40 °C. The crude ionic liquid is extracted with dichloromethane, washed with water until chloride is below 20 ppm, and dried on a rotary vacuum evaporator at 60 °C and ≤1 kPa. Water removal is critical because residual water shifts the electrochemical window and increases capacitance fade. In a symmetrical two-electrode cell with activated carbon electrodes, the electrolyte is filled under a −0.08 MPa vacuum and conditioned by galvanostatic cycles at 0.5 A·g⁻¹ between 0 V and 2.5 V. Production facilities dry the finished ionic liquid to <50 ppm water by ISO 760:1978; values above 500 ppm produce measurable gas evolution at carbon electrodes and reduce capacity retention after 5,000 cycles. Viscosity is measured per ASTM D445-21, and conductivity is determined by impedance spectroscopy at 1 kHz and 25 °C.
| Ionic liquid cation | Viscosity at 25 °C (mPa·s) | Conductivity at 25 °C (mS·cm⁻¹) |
|---|---|---|
| 1-Ethyl-3-methylimidazolium FSI | 18–22 | 15–17 |
| N-Butyl-N-methylpyrrolidinium FSI | 40–50 | 5.5–6.5 |
| N-Propyl-N-methylpyrrolidinium FSI | 38–44 | 6.0–7.0 |
Published data for specific production lots is limited; the ranges above reflect values reported under dry conditions. The direct use of bis(chlorosulfonyl)imide as an electrolyte additive is not viable because hydrolysis generates HCl and amidosulfuric acid. This boundary forces downstream users to maintain transfer-line moisture at ≤10 ppm and to avoid protic solvent carry-over.
Medicinal chemistry teams accept the dual electrophilicity of bis(chlorosulfonyl)imide as a route to unsymmetrical sulfamide cores. A typical batch procedure uses 1.0 eq of the imide in dichloromethane at −20 °C; a primary amine is added dropwise with 2.0 eq of N,N-diisopropylethylamine over 45 min. The first substitution generates a monosulfonamide intermediate that retains the second S–Cl site; its solution lifetime is 2–4 h at −20 °C but falls below 30 min at 0 °C. A second amine is introduced at −10 °C to produce the unsymmetrical sulfamide, which is quenched with 0.1 M hydrochloric acid. Ethyl acetate extraction, sodium sulfate drying, and concentration below 40 °C give a crude product with 70–85% UPLC area purity. Silica gel purification and precipitation from methyl tert-butyl ether increase purity above 95%. Isolated yields are substrate-dependent and fall between 35% and 55% for less nucleophilic anilines; the primary byproduct is the symmetrical disubstituted sulfamide from double addition of the first amine. This route is selected when the sulfamide motif is being evaluated as a zinc-binding replacement for a sulfonamide in carbonic anhydrase inhibition, but downstream process groups require chloride removal because residual chlorosulfonyl groups can quench later palladium-catalyzed coupling steps.
Agrochemical lead optimization transfers the same two-step aminolysis to continuous flow when a batch intermediate is unstable above −5 °C. The first feed—bis(chlorosulfonyl)imide in acetonitrile at 0.5 M—is held at −10 °C and mixed with a primary heterocyclic amine through a static mixer. Pyridine is added as acid scavenger at 0.9 eq relative to the amine. The stream enters a PFA tube of 2 mm internal diameter and 10 m length at a total flow rate of 10 mL/min, giving a residence time of 60 s at 0 °C. The monosulfonamide intermediate is cooled further to −15 °C before a second amine solution is combined at 0.5 mL/min and passed through a second tube with 90 s residence time. The output is quenched in-line into 5 wt% sodium bicarbonate at 0 °C, extracted with 2-methyltetrahydrofuran, and washed with brine. UPLC-MS area purity before preparative chromatography is 85–92%. Residual chlorosulfonyl species are tracked by ion chromatography after alkaline hydrolysis; the hydrolysis trap outlet is held below 0.2 area% before neutralization. This configuration reduces symmetrical sulfamide formation compared with batch mode and allows a narrower thermal window for heterocyclic amines that decompose at ambient temperature. Published data for specific agrochemical actives is limited, but the transformation is grounded in standard sulfamide bond-forming chemistry.
Parallel production of sodium bis(fluorosulfonyl)imide (NaFSI) for sodium-ion cells uses the same fluorinated intermediate and a sodium methoxide neutralization route. The HFSI is neutralized with 30 wt% sodium methoxide in methanol at 0–5 °C; the sodium salt is precipitated by solvent exchange with tert-butyl methyl ether. The slurry is filtered under nitrogen and dried at 100–120 °C in a vacuum oven. Electrolyte blending uses 1.0 M NaFSI in propylene carbonate with 2 wt% fluoroethylene carbonate. Half-cell testing against hard carbon electrodes starts with a formation cycle at 0.1 C between 1.0 V and 4.0 V, followed by cycling at 1 C. The chloride limit is set at <100 ppm because residual chloride accelerates aluminium current collector pitting above 3.8 V. Water content in the final salt by ISO 760:1978 is held below 120 ppm. Recrystallization from acetonitrile/toluene is used when methanolic neutralization leaves sulfate above 200 ppm; this step reduces chloride and sulfate and narrows batch-to-batch variation in sodium-ion electrolyte qualification.
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Bis(Chlorosulfonyl)imide (CAS 15267-77-3; molecular formula HN(SO2Cl)2; molecular weight 214.04 g mol−1) is a hygroscopic, low-melting solid supplied primarily as an intermediate for bis(fluorosulfonyl)imide salts and as a bifunctional sulfonylating reagent. The product is available in two model grades: BCSI-98 with a minimum assay of 98.0 wt% and BCSI-99.5 with a minimum assay of 99.5 wt%. In anhydrous form the compound appears as a white to pale yellow crystalline mass with a melting range of 36–40 °C. It reacts with water and protic solvents, releasing hydrogen chloride and sulfonyl-derived acid species. Closed containers are purged with dry nitrogen to a dew point below −40 °C and sealed in fluoropolymer-lined or Hastelloy C-276 packaging. The substance is classified as a corrosive solid under transport and supply regulations; the relevant safety data sheet must be consulted before handling.
The presence of two -SO2Cl groups bound to a single nitrogen center distinguishes bis(chlorosulfonyl)imide from chlorosulfonic acid, sulfuryl chloride, and aryl sulfonyl chlorides. Chlorosulfonic acid contains one sulfonyl chloride function and a strongly acidic O-H group; it is a dense fuming liquid with a boiling point near 152 °C. Sulfuryl chloride is a distillable liquid with a boiling point of 69 °C and is better described as a chlorinating agent than as a direct sulfonyl chloride monomer. In contrast, BCSI remains solid at ambient temperature and provides two electrophilic sulfur sites per molecule, allowing a single reagent to install two sulfonyl groups or to form the conjugated sulfonimide anion after fluoride exchange. The imide N-H is strongly acidic because both sulfonyl groups withdraw electron density; aqueous extracts exhibit a pH below 1 at 25 °C for a 1 wt% dispersion. This acidity and the absence of aromatic carbon make BCSI more suitable than aromatic mono-sulfonyl chlorides for electrolyte-salt processes where organic residues must be excluded.
Table 2 provides a comparative profile relevant to reagent selection.
| Property | Bis(Chlorosulfonyl)imide | Chlorosulfonic acid | p-Toluenesulfonyl chloride |
|---|---|---|---|
| CAS number | 15267-77-3 | 7790-94-5 | 98-59-9 |
| Physical state at 25 °C | Low-melting crystalline solid | Fuming liquid | Crystalline solid |
| Melting/boiling point | mp 36–40 °C | bp 151–152 °C | mp 67–69 °C |
| Sulfonyl chloride functions per molecule | 2 | 1 | 1 |
| Aromatic carbon | Absent | Absent | Present |
| Principal hydrolytic by-products | Hydrogen chloride and sulfonimidic acid derivatives | Hydrogen chloride and sulfuric acid | Hydrogen chloride and p-toluenesulfonic acid |
A representative specification profile for both model grades is shown in Table 1. The values are typical of bulk supply documentation; individual certificates of analysis take precedence.
| Parameter | BCSI-98 | BCSI-99.5 | Test method |
|---|---|---|---|
| Assay (wt%) | ≥98.0 | ≥99.5 | Non-aqueous acid-base titration |
| Moisture (mg/kg) | ≤500 | ≤200 | ISO 760 |
| Free chloride (mg/kg) | ≤1000 | ≤100 | ISO 10304-1 |
| Sulfate (mg/kg) | ≤500 | ≤50 | ISO 10304-1 |
| Iron (mg/kg) | ≤20 | ≤5 | ISO 11885 |
| APHA color | ≤100 | ≤50 | ASTM D1209 |
| Chlorosulfonic acid (wt%) | ≤0.5 | ≤0.1 | ISO 10304-1 after hydrolysis |
At chloride concentrations approaching the electrolyte-grade limit, the final lithium bis(fluorosulfonyl)imide specification imposes an upper bound on chloride in the chlorinated precursor. BCSI-99.5 with free chloride below 100 mg/kg reduces the burden on downstream precipitation and crystallization steps. In fluoride-exchange processes, chloride is released as HCl; incomplete conversion leaves residual -SO2Cl groups that later hydrolyze in the lithium salt finishing train. Batch end-point monitoring by in-situ FTIR or Raman spectroscopy is specified for the sulfonyl chloride S-Cl stretching region; conversion is considered complete when the residual BCSI signal falls below 0.05 wt% in the reaction mass. For BCSI-98, the same process may require an additional distillation or recrystallization step because free chloride and sulfate levels frequently exceed finishing column feed limits. Published data for this specific configuration is limited; process validation at pilot scale is recommended before scale-up.
On a 10 m³ fluorination line, BCSI is melted in a jacketed feed vessel at 42–45 °C under a dry nitrogen pad with a dew point below −40 °C. Transfer lines are heat-traced with surface temperature capped at 48 °C; low points in 316L stainless steel piping have caused solidification blockages when the product cooled below 38 °C. The material is therefore recirculated through a PTFE-lined loop until feed flow stabilizes above 1.5 t h−1. Anhydrous hydrogen fluoride is metered into the static mixer at a molar ratio of 2.05–2.2:1 relative to BCSI. The reaction mass is held in a C-276 reactor with external cooling at 5–10 °C and pressure below 1.5 bar g. The hydrogen chloride byproduct is routed to a packed scrubber operating with 20 wt% potassium hydroxide at pH 12–13. Frequent failure modes on this equipment include gasket swelling in fluoropolymer-lined pumps and acid creep through mechanical seals; double mechanical seals with barrier fluid at 1.0–1.5 bar above process pressure are specified. The process control window is narrow because low feed temperature causes line blockage, while high temperature above 55 °C accelerates hydrolytic decomposition and generates SO2 pressure excursions. Operators maintain the entire transfer and reaction system below 10 ppm water content in the gas phase, monitored by line-dew-point analyzers.
Hydrolysis of BCSI is fast and exothermic; contact with liquid water generates HCl and sulfonyl-derived acids. Bulk storage vessels are dried before filling and purged with nitrogen to maintain internal humidity below 5% RH at 25 °C. When ambient humidity exceeds 60% RH, transfer operations are suspended unless closed charge chutes with desiccant traps are used. The product is incompatible with alcohols, amines, DMSO, and alkaline aqueous solutions; combination with amine-based additives causes immediate sulfonamide formation and heat release. Materials compatibility data support PTFE, PFA, PVDF, and Hastelloy C-276 for wetted surfaces; 316L stainless steel is acceptable for short-term transfer at temperatures below 40 °C, but chloride stress-corrosion cracking risk increases with temperature and residual water. Ethylene propylene diene monomer seals are not recommended; perfluoroelastomer seals are specified for all flanges and pump casings.
Beyond the electrolyte-salt route, the compound is used in the preparation of sulfonimide ionic liquids and as a reagent for introducing bis(sulfonyl)imide functionality into organic substrates. Condensation with primary amines in anhydrous dichloromethane at 0–5 °C proceeds through the sulfonyl chloride groups; the second sulfonyl group is retained for further substitution or ring closure. Reaction control requires the addition rate to be limited so that the internal temperature remains below 5 °C; laboratory-scale calorimetric data show that exceeding this threshold increases the proportion of N-sulfonylated side products. Because the compound is a bifunctional electrophile, stoichiometric control of 1.00–1.05:1 molar ratio of BCSI to substrate is required for selective monosubstitution. The absence of aromatic carbon in BCSI allows downstream ionic liquids to be purified by aqueous extraction without introducing UV-active organic impurities.
Continuous fluorination of BCSI requires equipment selection that accounts for simultaneous HCl and HF corrosion. Bench-scale glass reactors are limited to screening reactions with fluoride sources such as anhydrous triethylamine trihydrofluoride; production lines instead use C-276 or PTFE-lined vessels. Because the reaction mass is highly acidic, glass-lined steel is not specified for fluoride-exchange service. The feed system is designed for viscosity behavior that changes sharply around the solid–liquid transition; at 50 °C the molten product flows under gravity, while at 35 °C it forms a crystalline plug. This property cliff imposes a minimum line temperature of 42 °C and a maximum of 48 °C for the jacketed pipe network. Start-up from cold requires heating the entire loop before introducing material; the procedure specifies a 2 h dwell at 45 °C and confirmation of no closed valves before feed begins. In continuous operation, the residence time is controlled between 20 min and 40 min by pump speed and reactor level; shorter residence times leave unconverted BCSI in the crude bis(fluorosulfonyl)imide stream, while longer times increase thermal degradation. The crude product is neutralized with lithium carbonate or lithium hydroxide in aqueous solution; the lithium salt is then crystallized and dried to moisture below 100 mg/kg under vacuum at 80–90 °C. Residual chloride in the final LiFSI is measured by combustion ion chromatography according to ASTM D7359.
